Calling Buckshot (and others)

[Rick N Bama]

In another post you told Keeper89 that he could get away with half the lube he used on a Loverin style boolit. Do I understand that all the lube grooves do not need to be filled for the lube to work properly?

Thanks

Rick

[David R]

I am not buckshot, but too much lube can cause trouble. I lube about the first 3 grooves. If its a light load, only 2 depending on boolit style. I have never filled all the grooves on my 311466.

My TC contender shoots better groups with only one groove filled in the C309113F (lee soupcan).

David

[XBT]

Rick, I am using a Loverin style boolit (Lyman # 266469) in my Swedes, seated out to an OAL of 2.800. This leaves the top two grooves exposed and unlubed. It works fine for me.

[beagle]

I only use 2 grooves on the 311465 and 311466. Usually, I'll do 3 on the 311467. So far, it's done well for me in the 30/06.

Lubes have really progressed since the old days when most of these designs were made./beagle

[Rick N Bama]

Well shoot, I never figured this could be part of the whole equation. I guess it's something else to test as if we didn't have enough things to ponder upon already. I'm just beginning to use this style of boolit myself being the owner of a new 311407 Group Buy mold.

Even if y'all ain't Buckshot, thanks.

Rick

[44man]

I have to wonder if it is because there is still too much lube in the grooves when it leaves the barrel, throwing the boolit out of balance in flight! I hesitate to say there is too much lube for the bore, just after it leaves.
Have any of you tried a very soft lube in all the grooves that would spin off the boolit when it leaves the muzzle? Might be a way to prove what is happening. Since I have no boolits like those, I can't test.

[45 2.1]

Have any of you tried a very soft lube in all the grooves that would spin off the boolit when it leaves the muzzle? Might be a way to prove what is happening. Since I have no boolits like those, I can't test.

I do the very soft lube with the loverins in all the grooves. If I use a slicker/heavier bodied lube, I use less. I have had no problems with the soft lube in all the grooves in my testing, but have had trouble with the harder lubes on this.

[StarMetal]

This lube spin off discussion has made me think. First let me say that I use to use Javelina, and that's a soft lube, especially during the summer, and I've found both rifle and pistol bullets with lube still in the grooves. Okay, here's what I was thinking. In another thread we got to talking about how many times a bullet would make a complete turn inside an animal's or human's body if hit with one. Let's say it's a 30-06 bullet shot from a rifle with a 1/10 twist. So theoretically that means the bullet would make one revolution in every 10 inches of flesh. If you remember I disagreed and said a bullet is really spinning. Then someone come up with, yeah the bullet in really spinning, but rpms means revolutions per minute. Okay fellows...if you go with that, then tell me how in the hell lube is going to SPIN off a bullet because first off rarely is a bullet in flight for a minute and if you figure the revoluitons for micro or even hundreths of a second, they are very very very low. Okay explain it to me.

Joe

[XBT]

I can’t explain it, Joe. I don’t know if the lube is spun off or not. I do know when I use soft lube my chronograph gets splattered with small bits of the lube. I don’t know if it’s being blown out the barrel or coming off the boolit in flight.


Rick, if you leave the top grooves of the Loverin style boolits unlubed, you can seat them farther out without the lube being exposed and making a mess. In my Swedes the longer OAL loads are much more accurate, that’s why I do it.

Jim

[StarMetal]

Jim,

My chrono too has lube on it, but think about it, your chrono is directly inline with the muzzle, if the lube was spun off I think the pattern would be so great it wouldn't hit the chrono, thus I think it's blown off from the gases and they would push it more straight ahead then scattered. Just my opinion.

Joe

[9.3X62AL]

I recall a conversation many years ago with a rangemaster of another agency, a small department in the Coachella Valley. They authorized just about every revolver, autopistol, or caliber that holsters were made for--and a number of the officers used S&W M-29's. To feed these beasts, Stan set up one of their loaders to seat Lyman #429421's over enough 2400 to enable 1200 FPS. He remarked that the loads worked fine, but splattered the 25 yard targets with bullet lube noticeably.

FWIW, he has advanced to high admin rank after transferring to my agency, and remains one of the good guys.

[StarMetal]

Well Deputy Al....if we're getting bullet lube on 25 yard target, which I certainly have too, that seems to eliminate muzzle gas blowing it that far. Soooo....that brings me back to bullets are spinning faster then what Buckshot says.

Joe

[felix]

The math is not hard, Joe, is it? Assume the RPM does not slow down much, surely no more than 10 percent by the time it reaches a resonable range. Assume the foward speed is 1000 fps by the time a 150,000 RPM boolit hits the target. Assume the boolit is going 200 fps when the target is exited, and at 100,000 RPM. Assume we are talking about target 3 feet thick. OK, now, just what is the question? ... felix

[StarMetal]

Okay Felix,

The arguement is that a bullet only makes one revolution equal to it's rifling twist. In other words if you have a 30-06 with a 1 in 10 twist, that bullet, when in flight or whether in the barrel yet, only turns one revolution in 10 inches. When you figure up rpms for a bullet the letters rpm meand revolutions per minute. So let's take an answer that gives you 150,000 rpms that you figured up using the data of muzzle velocity and rifling twist rate. Now if you divide that 60, which there are 60 seconds in a minute, that give you 2500 revolutions per second (rps I guess we can say). Well we know that generally a bullet is not in flight for a minute unless you're shooting it straight up in the air or at a very steep angle. Time of flight to a target say at 100 yards is very short. Let's use the Lyman 311284 bullet at 2000 fps shot out a 30-06 with 1/10 twist. That gives us an rpm of 144,000. Now divide that by 60 seconds and that gives us 2400 revolutions per second. Okay, in the Lyman cast book it says time of flight to a 100 yard target is .159134 second. So we can round that off to .2 seconds. Now let's figure how fast the bullet is turning in tenths (1/10) of a second. We divide 2400 by 10 equals 240 revolutions per 1/10 second. So Lyman says it takes .2 seconds to get to a 100 yard target so we multiply that 240 by 2 and get 480 revolutions. That supposely is what the bullet is spinning hitting the 100 yard target. Am I correct or even close? So why is that bullet revolutions are figured per minute? I stll think bullets are spinning faster when they hit things. That's the arguement Fellx.

Joe

[357tex]

starMetal
look at it this way a 30 06 with 1 in 10 twist, ever 10 in to the target it makes one revolution.100yd is 300 ft or 3600in.and you divide that by 10 .Your bullet turns over 360 times .in a real short time.

[grumble]

Joe, the argument you're making reminds me a whole lot of your support for the term "starboard." <GGG>

[StarMetal]

Grumble

It's a fact that any caliber with a faster twist has more bullet impact energy then the same caliber with a slower twist with the same componants and velocity. So far nobody seems to know why on the forum...I say it has to do with bullet rpms.

If you have an idea or theory to contribute..please, by all means do so.

Joe

[felix]

There is no argument, Joe. What you figured is pretty darn close. You have to keep in mind the boolit can still be rotating when at a dead stop in the foward direction. In soft meat and with an unequal expanding boolit, you can get a buzz saw effect. There is no doubt about that. I see it in river mud all of the time. ... felix

[grumble]

Ok Joe, you want serious instead of joking? I can do that. Sometimes, anyway.

You're wrong. There is NO more "impact energy" in a spinning boolit than in a non-rotating bullet. Energy is a function of weight and velocity, nothing else. A spinning boolit may be thrown off its axis, causing a gyroscopic tumble. The tumble may impart a small amount of rotational energy to the resistive mass it hits, but that will be negligable. The effects you see in game is because the boolit is no longer in a nose foreward attitude, but instead is presenting its profile (or a portion of the profile, depending on its yaw and pitch) to the tissue as it passes.

RPM is insignificant, other than to stabilize the boolit in flight. And, the boolit can never spin at a faster rate per unit distance travelled than the pitch of the rifling.

Did that help? At least it was serious. <G>

[StarMetal]

Well....just got off the phone with Sierra ballistic lab. Told him of our little debate about bullet rpms. He got a good laugh, but bottom line is he said all of you that think that what ever the rifling twist is, is all that bullet turns in that distance....example: 30-06 with 1 in 10 twist so the bullet only turns 1 time in 10 inches of whatever it's going through....ARE ALL WRONG , that I was right. The bullet is spinning those very high rpms, in other words if you have a 30-06 shooting a 150 gr bullet at 2700 fps out of a 1 in 10 twists the bullet is spinning 2700 x 720 divided by 10 to equal 194,400 rpms as soon as it comes out of the muzzle!!!!!

Well I'm finished, you nay sayers take it up with Sierra, Hornady, Speer and any other ballistics engineer you wish to discuss it with.

Faster the twist, the more energy impartedin the bullet, the more destruction on the target.

Joe

[45 2.1]

Joe is correct. Work thru the units and it will give his answer.

FT/SEC X 60 SEC/MIN X 1 ROTATION/10" X 12"/FT = ROTATIONS PER MIN.

[StarMetal]

What most shooters who go to the overly heavy and overly long bullets
never stop to realize is when you rotate a projectile 25% faster the
quality of the bullet must be several times better quality to fly
equally well. Which they are not! A 165 grain 7 mm jacket is just as
ununiform as a 140 grain. Quality match bullet jackets will run from
.0002 to .0005 thicker on one side than the other. This goes for a 240
grain 30 cal bullet. If you fire a 240 gr. 30 call bullet at 2600 fps
out of a 1 in 8 twist the rotational spin is 207,999.99rpm as compared
with a 190gr. fired out of a 1 in 12 twist at 3000fps doing 180,000
rpm. With both bullets being of the same quality and having the same
variation of bullet jacket thickness it doesn't take a Ph.D. to know
which one will fly the truest. Calculate the centrifugal force on a
jacket rotating 207,999 rpm. When you rotate a thin jacket that fast
out of eve 20 rounds you will sling a jacket loose and the core will
rotate at a different speed than the jacket. Ask any high power shooter
who shoots a 7 mm mag how many times he has been drilling the 10 ring
and have a round never get to the target. I spent 30 days working with
the Navy Seals evaluating the 240 and 250 gr. 30 cal bullets out of a
300 W ma. I built two rifles identical except one was an 8 twist and
one was a 12 twist. One to shoot 240 and 250 gr. bullets and one to
shoot 190 gr.We laid two shooters on the line with instructions to take
a dead hold and fire on command of the coach. The coach tried to call
the most opposite conditions that he could. When we scored each target
and figured the most drift the 190s out shot the heavy bullets by a
considerable amount. Since that test the Navy has adapted the 180 gr.
match king. This was not just a few targets but 8 hr. a day 5 days a
week for a month. When it was completed I rebarreled their 1 in 8
barrel to a 1 in 12. Things like the tests we ran is what keeps me from
being a heavy bullet fan.You can imagine what would happen to a 190 shot
out of the 1 in 8 at 300 fps faster and that increase in rotational
speed over a 250 gr.

Gale McMillan

[StarMetal]

Guys, here's simple explanation. Remember the big toy spinning tops whe had as children (this is if you're 55 or older). They were made of metal and were about 8 or inches round and had a knob handle on top that you pulled up on and a shaft would come up and have spiral grooves cut into it and the way they worked is you would pump that grooved shaft up and down into the top and because it had male grooves that engaged those female grooves in the shaft it would impart a spin to the top. Now if you remember that top would spin pretty damn fast.....alot faster then whatever the twist was on that grooves shaft. A rifled barrel does the same thing to a bullet, that bullet is spinning faster then whatever turn in whatever inches the rifling twist dictates.

I rest my case.

Joe

[44man]

Joe, I was searching for my information on spin and could not find it and then I read your last post which is correct. The higher the velocity is will also increase the rate of spin. So let's face it, the bullet is HUMMING and it will spin off a soft lube very easy. A real hard lube will also spin off but can leave traces left in the grooves that are not even.
A friend sent me some boolits with a red lube in the grooves. Most had fallen off into the bottom of the box he shipped them in. The rest was a job to remove with some having to be scraped out of the grooves. I would not shoot that brittle stuff! I can picture chunks of it flying off and the rest remaining on the boolit to throw it out of kilter.
The solution is to get the consistancy right so the lube leaves evenly and anything left is distributed in a balanced condition.

[grumble]

I think I've figured out why Joe's guns are so accurate. He makes boolits that GAIN energy after they leave the muzzle. Now, that's something we should all aspire to! <GGG>

[StarMetal]

Grumble

They don't gain eneryg, it's already imparted into it from the powder and the rifling twist, which basically is still the powder burning and pushing it through the barrel, which makes it spin.

You can all laugh, but you all know I'm right too.

Thanks to enterprising experimenters and rookie scientist like myself, you benefit from my labor and thinking Grumble.....and you're welcome.

Joe

[grumble]

Grumble
...

Thanks to enterprising experimenters and rookie scientist like myself, you benefit from my labor and thinking Grumble.....and you're welcome.

Joe

Can't tell you how much I appreciate the free education, Joe. <GGG>

Now you got me confused, though. I thought you had bee saying all along that the boolit was turning more than one revolution per foot of travel when shot from a 12-twist barrel? That's what everyone has been trying to say, that the spin on the boolit can't exceed the twist of the barrel.

[StarMetal]

Well it does, by alot.

Joe

[grumble]

Well, in a way, I supose. The boolit's forward velocity slows down much faster than the rotation, so while the boolit may start out at the same number of rotations as the twist per foot traveled, as it slows down along its path, it will still be spinning at about the same rate, so it may turn more than that number of revs per foot.

But, it won't be going at a higher rate of spin, just more spin per foot traveled.

[StarMetal]

That's were your old mummified thinking is wrong...but you go right ahead and keep thinking along those lines. Guess you never got your top to speed up so you tossed it into the toy junk pile.

Joe

[grumble]

Sigh. OK.

[waksupi]

Guys, here's simple explanation. Remember the big toy spinning tops whe had as children (this is if you're 55 or older). They were made of metal and were about 8 or inches round and had a knob handle on top that you pulled up on and a shaft would come up and have spiral grooves cut into it and the way they worked is you would pump that grooved shaft up and down into the top and because it had male grooves that engaged those female grooves in the shaft it would impart a spin to the top. Now if you remember that top would spin pretty damn fast.....alot faster then whatever the twist was on that grooves shaft. A rifled barrel does the same thing to a bullet, that bullet is spinning faster then whatever turn in whatever inches the rifling twist dictates.

I rest my case.

Joe

Joe, that's BS. If you remember, you would reach a point where the top wouldn't go any faster. A bullet does not spin fgaster when it leaves the bore. It immediately begins loosing rotational speed, as did the top.

Physics 101

[StarMetal]

Ric,

Yeah, that's why you claim those long 6.5 cast bullets get bent by high bullet spin rpms huh.

Remember beagle compared the 6.5 bending as it exited the bore to spinning a copper wire in a drill? Well Ric I hate to tell you that 3, 4, or 500 rpms isn't going to bend a bullet or a copper wire in a drill.

The top can't be spun any faster because you can't pump the shaft much faster.

You all need to go to physics class.

Joe

[StarMetal]

Oh yeah Ric,

One more thing, if increasing the velocity on the Swede causes the bullet to bend from higher rotational forces how can that be if it has a fixed rifling twist? hmmmm? 1 in 6.75 or 1 in 7 is still 1 in 6.75 or 1 in 7 no matter how fast forward the bullet is going, so you fellows say.

Joe

[waksupi]

All I am saying, is rotational speed does not increase after the bullet leaves the barrel. It's the difference of pushing a bullet through the bore with a cleaning rod, or shooting it. Still the same rate of twist. The bullets bending after they leave the bore, or AS they leave the bore, has nothing to do with increased rotation in the air.

[StarMetal]

What bends them then Ric?

Joe

[357tex]

StarMetal
Lets take a 1 in 12 30 cal.twist .If we are shooting at 100 yards.At 1500fps. it rotation is one turn in one foot so it turns over300 times to get there. Then we shoot it at3000fps and it gets there 2 times as fast, But still only turns over 300 times befor it gets there,the rpms are double but it still only turns over 300 times.
:redneck:

[porkchop bob]

What bends them then Ric?

Joe
To my thinking, the bullet is supported by the barrel. That support stops upon exit of the bullet. On longer bullets, the tail end is still supported by the barrel and the front end is not. At that point a thin jacket is most likely to fail. At very fast speeds, the bullet may travel a bit before the inital crack extends and the bullet just comes apart. At slower speeds, it just bends.
Bob

[Blackwater]

Joe, I think what's happening is simply that the faster twists impart enough centrifugal force to the bullet that it causes the bullet to come apart and fragment more easily, thus producing the "hand grenade inside the chest cavity" effect. A bullet's spin around its longitudinal axis is sorta' trying to "throw off" the outermost surface layers of metal due to the spin rate, just like Little David's sling that he slew Goliath with. At some point, a bullet, cast or otherwise, CAN be spun fast enough (velocity helps here, of course, since it accelerates spin as well as the twist rate) that it'll just sling itself apart due to centrifugal force. This, as I understand it at least, is why the Swift and .22/.250's are notorious for "blowing up bullets in flight."

As the swifty bullet is fired, it's impelled at high velocity, and spun at a very high rate. It's said that the core becomes molten due to friction with the air and other factors, and that the nose cap of a PSP type bullet remains solid only due to the extremely high air pressure at the tip. The air, more or less, keeps the pressure high enough that the little lead tip can't go molten.

If the jacket, in the case of J-bullets, is thin enough, and the core soft enough, and the spin rate (regardless of how it's measured and cited) high enough, the bullet will simply come apart by the molten core breaking out the sides. When the centrifugal force is high enough, and the heated jacket (again due to friction) gets soft enough, the bullet becomes a gray-blue puff of smoke and the bullet doesn't ever hit the target, except maybe in molten droplets if it waits until it gets close enough to the target to completely blow. The jacket split, the extremely high air pressure catches the flattened pieces of jacket material, and they go wafting off somewhere like mishapen frisbees, so rarely hit the target.

Lead bullets having no jacket to retain them longer, will generally just show poor accuracy if cast too soft and driven too fast before blowing up in a blue-gray mist, but at some point, any bullet, according to its mixture, diameter, etc., CAN be spun fast enough to cause the centrifugal force around the longitudinal axis to simply start deforming, I'd think, thus inducing wobble, yaw, or whatever. It'd take a hard bullet metal to withstand really high velocities with a cast bullet, which seems to be proven out by experience, if only vicariously in my case. I'm still learning the applications of cast bullets, but the physics are pretty clear, or at least seem to be to me.

Now, who's gonna' blow THIS theory all to helenback??? ;)

[Blackwater]

Well just DUH! I didn't read page 2 until after posting. Nevermind.

I think I'm gonna' go pour myself a small adult beverage, and set back an' watch.

[StarMetal]

357tex,

Wrong....let's take that example for the lyman book, that 311284 shot at 2000 feet per second. So we are working with a one in 10 twist...that's one turn in ten inches. So let's figure how much of a foot 10 inches is, so we divide 10 by 12 inches so that's 10 divided by 12 = .8333333 so 10 inches is .8333333 foot. So how many of those .8333333 feet are there in 2000 feet. 2000 divided by .8333333 = 2400 or them. That means it did 2400 ten inches in one second, right? And that also means that bullet turned one time in every 10 inches in 2000 feet in one second and thats 2400 turns. Now that we are speaking turns and we want rpms we have to multiply that 2400 by 60 being there are 60 seconds in a minute. 2400 X 60 = 144000 rpms. Now if you go back up to my post where I calculated the rpms of that bullet you will see it is indeed 144000.

Voila !!!!!!!!!

Telling you, you fellows are wrong.

Joe

[StarMetal]

Blackwater,

Exactly, I agree with you. But these fellows are saying that a bullet isn't really spinning 100's of thousands of rpms. They say if you have a rifling twist of say 1 turn in 10 that, that bullet only turns one complete turn in 10 inches of travel through flesh, if it happens to be hitting flesh and they are full of horse hockey. That bullet is spinning many many complete revolutions.

Joe

[Maxthompson]

Fellas,

The reason the the boolit is going more than one revolution through the ten inches of flesh is because once it hits something it slows down dramaticaly in forward motion but does not slow down spinning.
If it hits a bone or hard object it still spins at whatever rpm it was started at.

Granted the spin will slow down but not nearly as quickly as forward progress.
I have spoken.

Mike

[357tex]

starMetal
you sure we are not saying the same thing ,just in different ways? :lovebooli

[StarMetal]

357tex

Positive...that example of the lyman 311284 at 2000 fps is indeed spinning 144,000 rpms...here call Sierra, ask them 1-800-223 8799. I warn you, they will laugh at you.

Joe

[StarMetal]

The real truth is the bullet is spinning 720 X velocity divided my the twist, but you fellows are dummies and can't see it.

Joe

[357tex]

starMetal
I could be wrong ,often am. It is easy for me to get in over my head.But I need to understand things.Often can't rest untill I do. :-?

[waksupi]

What bends them then Ric?

Joe

It might be little Swedish demons dancing on the nose, for all I know. Centrifugical force would be my guess, though.

That wasn't my point. My point was, once the bullet leaves the barrel, there is no outside influence to increase it's speed of rotation. If you can make them do that, you have the makings of a perpetual motion machine. As far as rotation passing through a body, they may well indeed spin faster than when they left the barrel, due to the penetration of mass, as was mentioned.

Rotational force is also lost, the further the bullet gets from the launch platform.

Where's Sir Isaac Newton, when we need him?

[357tex]

StarMetal
You are right it is spinning at 144k
But like I said you cut the speed in half it cuts the rpms in half.
Do the math 720x 1000fps divided by 10 = 72k rpms
So we were saying the same thing. And maybe I am not a dummy.

[StarMetal]

Ric,

Leaving the barrel and gaining speed isn't my point either, that is in rpms. It's already got those in the barrel just as it got it's velocity in the barrel. What you fellows are missing is the time here. The rifling twist is a mechanical mechanism to give a bullet the rpms it needs. You all are hung up on this 1 in so many inches things. Let's try this, lets go to cars.

Let's say we have a car with small tires. Let's say the circumferance on those tires are 10 inche. So that tire makes one complete revolution in ten inches. Nothing is going to change that except rubber wear. Don't give me any smartass answers like burning rubber and the tire is slipping then. Okay. Now lets speed that vehicle up to 200 mph. Those tires are still making one turn every ten inches. Now 200 mph is 12,672,000 inches per hour. Divide that by the 10 inches it takes for the tire to make one revolutions and we find that is 1,267,200 revolutions. Now we divide that number by 60 to get rpms which is 27,720 rpms. That's the rpms of that tire or tires. Now, if you happen to hit a man crossing the road while you're doing that 200 mph did your tires go through him/over him one turn in 10 inches or at 27,720 rpms????

....and just to make your heads spin (no pun) or is the answer both?

Joe

[StarMetal]

357tex

No you're not a dummy, what the arguement here is Buckshot says, although that bullet is spinning 144,000 rpms, it is only making one turn in 10 inches of flesh when inside someone's body...and that is wrong, it's really spinning....whatever the 144,000 rpms have degraded to by air resistance, gravity, and friction from the flesh. . Like I said that 1 in 10 rifling twist is a mechanism to get that bullet to that 144,000 rpms at that velocity of 2000 fps.

Yes you are correct if you cut the velocity or twist, the rpms are going to drop big time.

Joe

[Buckshot]

...............Please forgive me if this has been answered. I only read the first few replys to the post before resopnding to the issue of a slug spinning off lube or not. I suppose I'll find out if I'm being redundant or not, as after I post this I'll go back and read the entire thread.

For the sake of my rather simple math abilities (if I'd have been rich, I'd have paid some other kid to sit my math classes!) please allow me some easy numberes to deal with here. While possibly NOT exact, they should suffice to prove the premise.

1) While a bullet is only making one turn in 10 inches (say), we'll suppose it's spinning at 200,000 rpms. Can it spin off lube? Most definately it can.

As an example we have a tire that is 30" tall. It's circumfrence is 94.2". If you turn off a muddy road onto pavement can you hear the mud being slung off? And you're doing maybe 15 mph?

Lets take that tire and compare it to our 30 cal bullet doing 200,000 rpms. At 60 MPH, which is 1 mile per minute it travels 5,280 feet in one minute. Divide 5,280 feet but the 94" diameter of the tire. We then find in one mile the tire rotates 674 times, or 674 RPM.

Has anyone ever seen a hubcap come off a wheel? Does it just flop right there on the ground, or does it have rotational energy which causes it to roll on down the road or bound off in some direction if it hits something?

So okay now, you say sure my tire slings off mud and hubcaps and wheel weights and stuff but it's so big the centrifical force is huge. I will grant you that. On those merry go rounds at school or the park, if you stand close to the center of rotation you feel less then if you were standing on the rim.

So we have a .308" bullet, which is .96" in diameter. It's about 1/100th the circumfrence of our tire. If it were spinning at 674 rpms I will most unscientificly suppose it MIGHT have 1/100th the rotaional force to eject lube. But it is in fact spinning at 200,000 rpms (for at least a portion of it's flight).

To give an idea for apples to apples comparison lets use SFM or Surface Feet per Minute. This gives us a comparison of surface rotation past a fixed point. If you will, as if the object had 0 forward motion but was merely spinning in position with a pointer indicating one spot. Our bullet and the tire each have a pointer pointing at them as they spin in place and a dial ticks off one RPM for each complete rotation.

Clear as mud 8)?

So we take the tire of 94" diameter and draw a chalk mark across the tread and while it spins there in the tire balancer doing an indicated 60 mph, or 674 rpm's, that gives us 5,280 SPM or Surface Feet per Minute.

Now take our bullet and put it on the Ultra super full race tire balancer and spin it at 200,000 rpm. The bullet is .96" in circumfrence as we figured earlier. So each rotation is .96" vs the one tire rotation of 94". So we multiply our 200K rpm by the .96" circumfrence and we get 192,000 inches. We then divide by 12 to get feet and the result is 16,000 Surface Feet per Minute for the bullet.

So we'll say the bullet is then rotating at 3.03 times the Surface Feet per Minute of our tire. 16,000 / 5,280 = 3.030303 etc, etc.

So why can we still find lube on our bullets at 50 or 100 yards or maybe further? We can see that while 200,000 rpms is extremely fast, in actuality the surface feet per minute past a certain point is only 3 times that of a car tire at 60 MPH. But a point of fact is that while it's SPM rotation is only 3 times the tire's, it's forward velocity is an equine of an entirely different hue :-)

At 3000 fps it takes our slug only about 1/20 second to go 150 ft/50yds, and about 1/15 second to go 300 ft/100yds, etc. As may be seen, the spinning force is minor compared to the forward energy of our spinning slug.

And yes, if the barrel has a 1 turn 10" twist, upon exit the bullet will also make only one revolution per each 10" of forward travel. It cannot be otherwise or it would violate a bunch of physics. It's rotation can only slow as a result of friction with the air, and friction there is. If the bullet were to suddenly INCREASE it's rotational velocity, it would have had to gotten an addition of energy from some source outside the firearms' influence.

..................Buckshot

[shooter575]

I have read this entire thread,My head hurts and I got to go to work

[45 2.1]

Sounds like you didn't skip most of your science classes there Rick.

[XBT]

I don’t know about the boolits, but after reading this thread my head is sure spinning.

One thought: I have seen many high-speed pictures of boolits hitting things and have never saw a target react to the spin of the boolit.

I have also seen lots of recovered boolits that had the classic mushroom shape, but I have never saw one that showed any twist or directional set on the pedals of the expanded boolit.
This seems to indicate that regardless of how fast the boolit is spinning, the spin has little or no effect on the target.

[felix]

Bravo, Buckshot! Very good job. YOu have a couple of typos where you meant circumference instead of the word diameter. A typical 15 inch tire is around 90 inches in circumference, not diameter. Your logic corrects for the typo, so the expo is easy to understand. ... felix

[Char-Gar]

You boys shure are having fun on this one. It is a dicussion worth having and I wish we could come to agreement. I am an artist, phlosopher type who is concerned about the mysteries and angst of life and leave all the numbers and physical stuff alone.

However...I have always held the opinion that once a bullets is free from the constraints of the barrel, it would pick up RPS for a while. Certainly down range, gravity and air resistance will start to degrade that. But, for a time, the bullets enjoys it's freedom and that pent up energy expresses itself in more spin.

This is why too much spin on an alloy bullet can twist them into screws or cause them to come to bits.

Don't shoot me boys..I am just a simple minded country preacher who likes the smell of burning gunpowder.

"Why is a mouse when he spins?..The higher the more."

[StarMetal]

Buckshot says: So we have a .308" bullet, which is .96" in diameter. It's about 1/100th the circumfrence of our tire. If it were spinning at 674 rpms I will most unscientificly suppose it MIGHT have 1/100th the rotaional force to eject lube. But it is in fact spinning at 200,000 rpms (for at least a portion of it's flight).

Then he says: And yes, if the barrel has a 1 turn 10" twist, upon exit the bullet will also make only one revolution per each 10" of forward travel.

Geez, talk about tongue twisters and mind bogglers.

First lets tackle the hubcap coming off a wheel. Yes indeed I've seen a hubcab come off and move the once. And yes it has alot energy too, scoots down the road (which I'll mention more about here) bangs things, bounces all over the place. I sure wouldn't want to get hit by one. Now what I wanted to say about it spinning down the road, ever notice that the car it comes off of is say doing 60 mph and the hubcap comes off and then spins past the car it come off of.....duh....how can that be when it. We all know the answer to that huh.

Another thing I read when I use to get the Chevy High Performance magazine is about the 200 mph club. That is were you build a car to do 200 mph or more. This one fellow had a Chevy Impala. One day he's testing at I think it was 190 mph and the left front tire blew (Grumble..for you that is forward port tire) and everyone was amazed at the damage it did. First it tore off the whole fender. The amazing thing is part of the tire made it through the firewall. Lot of energy there.

So what is it Rick, the bullet is spinning 200,000 rpms or just one turn in 10 if it was fired fromt hat twist? I think you too need to call Sierra 1-800-223-8799.. Ask for the ballistics tech...they're the dummies that don't know crap.

XBT

Just exactly what would you expect a target to do being hit by high rotational force of a bullet? I'll tell you what to expect, ok? Same thing as when you drill a hole in a piece of wood for example, you pull the trigger on the drill the bit starts spinning fast, you touch the wood and it starts boring a hole in it. That's it. Now if you want a picture of a bullet (hollow point) that expanded and the pedals show rotation force I have one and will take a pic of it and show you. It was shot into water. It was a 115 gr 9mm hollowpoint.

Felix

Whatya mean Bravo Buckshot? All he explained with his usual long winded post is that centrifical force flings things off a spinning object. He didn't explain what rpms a bullet is really doing, but he did say at one point it was doing 200,000 rpms, yet at another on one turn in 10 inches. Typos , hypos...we're all old and sometimes your fingers just do what they want. I don't pay attention to other's typos...its nothing.

So I guess someone is going to have to call MIT or NASA and get to bottom of this bullet spin.

Joe

[felix]

Joe, go ahead and call NASA. In 1986 at Redstone you'd might have talked to me. ... felix

[StarMetal]

Well then Felix...figure it out for us. We have inquiring minds.

Joe

[grumble]

OK, one last try.

For ease of calculations, let's say we have a boolit spinning at 120k RPM. Divide by 60 serconds/minute, and that's 2000 revs per second (RPS).

Now let's say the boolit is travelling along at a velocity of 1000 fps. That means it will take the boolit 1/1000 of a second to travel one foot. So, the number of times the boolit will spin in that .001 seconds is (.001sec x 2000 RPS) or 2 turns.

You can plug in other numbers using a simple equation:

(RPM/60) x (distance in feet/velocity in FPS)=number of revolutions in that distance.

If we can't agree now, I REALLY give up.. <G>

[sundog]

yea, been following along here. And, rotation and velocity will begin to degrade as the boolit leaves the muzzle. In fact, because the pressure curve decreases before the boolit clears the bbl, it can actually be decelerating while it is in the bbl. Rotation remains constant until it leaves the bbl. Neither velocity nor rotation can increase after it leaves the bbl as there is no force acting on it to do that.

A body at rest tends to remain at rest, and a body in motion tends to remain in motion..., UNLESS ACTED ON BY A FORCE. Did I get that right?

I missed something on the hub cap thing. How can it accelerate after it is detached? sundog

[Pilgrim]

I wish I could figure out what the argument is about!

A bullet cannot spin faster than the rotational forces placed upon it in the barrel. Those rotational forces in the barrel are represented by the spin as all of you have calculated. A faster spin is physically impossible. If it spun faster, some force outside of the barrel would have to act on the bullet, and there ain't any of those. Similarly, a slower rate of spin could only result by the bullet stripping, and that ain't happening in this discussion or all of your calculations re: rpm's would also be hosed up. That said, at the instant the bullet leaves the barrel, the twist and linear distance traveled have to mathematically be identical as they are physically linked and inseperable. At an infinitesimal distance outside the barrel, the linear velocity will have decreased as will the rotational velocity. HOWEVER, the forces that retard linear velocity are much greater than those that act on the rotational velocity. Thus, the linear velocity will decrease more rapidly than will rotational velocity. As a result, at whatever distance outside the barrel you select, the turns per unit length will be greater than the turns per unit length that existed when the bullet left the barrel. In other words, if the twist was 1:10, at the instant the bullet left the barrel the twist would match the linear distance (in this case one turn in 10" of travel). At 100 yards, the velocity may have decreased by a factor of say 0.2 (3000 fps down to 2400 fps)while the rotational velocity may have decreased by a factor of maybe .05 (200,000 rpm's down to 190,000 rpm's). As a result the bullet will turn more than once while traveling the same 10". BUT the bullet can NEVER turn faster than the original 200,000 rpm's. To do otherwise would violate all of the laws of physics.

BTW - Starmetal...lest you insinuate I also am an idiot, you should know that I've studied those laws of physics (all of them) up through quantum mechanics and beyond, as well as the thermodynamics that accompanies those studies, as well as the mathematics needed to understand quantum mechanics and thermodynamics (and other stuff). It is highly unlikely (although not impossible) that the technicians at Sierra have acquired anywhere close to the formal education that either felix or I have suffered through. If they had, they wouldn't likely be at Sierra answering phones as they would be making much more $$ elsewhere. FWIW..Pilgrim

[9.3X62AL]

Pilgrim--

THANK YOU for clearing up a question that occurred to me long ago--whether the spin rate degraded at a faster, slower, or same rate as the forward velocity. I had a general empirical feeling that spin rate did NOT degrade as fast as velocity did for the reasons you indicate--fewer forces acting on the projectile to cause such a degradation. Not having the benefit of deep study in mathematics and related scientific fields that you and Felix have, I can only guess at such things.

[Scrounger]

If I interpret Pilgrim's learned reply correctly, what he's saying is that if two bullets leave the barrels at the same time and same velocity, the bullet with the 7" twist (.223) will have a highr RPM down range than the bullet with the 14" twist (.22-250). The higher initial velocity will factor into that equation but it is probably less than you think, probably 500 to 600 FPS. Both bullets will naturally lose velocity the farther they go, further degrading the velocity difference between the two.

[StarMetal]

Well there you have exactly what I've been saying, the formula to figure out rotational spin is correct and the bullet is spinning very high, like for example 200,000 rpms...and if it's that when it hits the target that's what it is spinning at, 200,000 revolutions. So there is some rotational energy put into a target. That explains why my 1 in 7 twist AR tears up more game.

Joe

[grumble]

"...So there is some rotational energy put into a target. That explains why my 1 in 7 twist AR tears up more game."

Aaarrrrggggghhhhh!!!!

[StarMetal]

Pilgrim said: A bullet cannot spin faster than the rotational forces placed upon it in the barrel. Those rotational forces in the barrel are represented by the spin as all of you have calculated.

That's what I have been saying all along. That the rifling twists imparts the rotational spin to the bullet. Just because it's 1 in 10 doesn't mean that the bullet is only turning one time in every ten inches, that sucker is spinning some high rpms. Like Pilgrim said, and they are high when they hit something.

Pilgrim, I'm not calling you an idiot or anyone else, I said dummies by the way, and I think some are if they think a bullet isn't actually spinning very high rpms through the air and also if they think that a bullet shot from a faster twist doesn't do more damage on game, such as a praire dog.

Joe

[grumble]

Ok, Joe. Use the equation previously posted. How many times will the bullet turn as it passes through a prairie dog?

How much damage will that number of revolutions do?

[StarMetal]

Grumble,

None, it'll blow up.


Fellows,

I didn't get any pm's from moderators, so this is on my own. I apologize if I stepped on anyone's toes and for saying some of you are dummies. Actually a person who may know something should try to make the effort to help those that don't and because they don't doesn't mean they are dummies. So for that I'm sincerely sorry. I just got frustrated trying to explain what I saw and know. I have two 223's, one is the AR15 with the 1 in 7 twist you hear so much about and the other is a Model 70 Winnie varminter with a 1 in 12 twist. I know using the same bullets and loads that there is a major difference between what that bullet does to a praire dog and groundhog, and cat between being fired from those two different twist rifles. I can't tell you the number of guys that I hunted those animals with that had 22-250's with soft points or hollow points that were just amazed at how the bullet fired from the AR15 obliterated those small varmints. It may not be so much the energy in the rotation of the bullet, but that the high rotations coupled with the forward velocity makes those bullets come apart when hitting the varmint alot worse then a lower spin one.

Grumble,

Assuming the bullet doesn't lose any spin, which we know it will, just change the rpms to revolutions per second and multiply that times the time of flight for 100 yards that Lyman gave. Remember, that's only a 2000 fps cast load not some zipping along 224 bullet at 3600 rpms out of a fast twist barrel.

Joe

[grumble]

I didn't understand your last comment, Joe. Not sure what you were telling me.

I think you can explain the increased tissue damage to bullet tumble being faster at the higher RPMs from the 1:7 barrel. Like tipping a gyroscope or bicycle wheel, it "jerks" into a new stable position. From that point of view, the rotational energy will cause more damage than a non-spinning (or slower spinning) bullet would do because it presents more surface area to the tissue. But, one or two turns of a bullet passing through flesh along its main axis wouldn't make any difference.

I sense that maybe we're coming to closure! Hurray! <GGG>

[Scrounger]

Joe, I have seen too many bullets kick up dust behind the (hit) animal and go skipping across the prarie to buy the bullet blow-up theory. It will expand, it will kill the animal and transmit a lot of energy to it, but the few ounces a prarie dog consists of will not disentigrate a bullet in my opinion. Experiment: Take a plastic half-liter soda bottle filled with water. This is twice the mass of a prarie dog. Set a cardboard target immediately behind it and shoot through the water. Any holes in the carboard? I haven't tried this so I'll take your word for the results.

[StarMetal]

Art,

If I set a one gallon milk jug up with water and shoot it from 100 yards with my AR15 and Hornady 60 gr V-Max, it's iffy if I'll see anything on the cardboard behind it. If I shoot a milk jug with anything including my 223 Winchester varminter, it just more or less splits it. That same jug shot with the AR15 and bullet described explodes and shattered. That shattered part is what got me, the plastic milk jugs are made from are not brittle, it's very elastic, thus why most bullets just split it. I posted a pic of that jug, let me see if I can find in here.

Grumble,

I'll try to explain that. Here goes, bear with me. It's kind of like the bullet becomes very frangile because of one thing it's spinning very near the limit of it's structural strenght. With that happening it doesnt' take much to make it come apart. Where as bullet that isn't spun near that limit merely hits the animal and starts to expand. Now if you think most all the varmint bullets from the various manufacturers are structurally made thin, made to come apart easily. Look at Speer's name for their explosive bullets "TNT". So the thing with my AR15 it doesn't have to be a thinly structured bullet, that 1 in 7 twist spins it up so fast it becomes fragile. Let's figure the spin for say a 55 gr bullet at 3100 fps. So that 720 X 3100 fps divided by 7 for the twist. It comes out to 318857 rmps...that's spinning buddy. Let's do it for a 1 in 12 twist. 720 X 3100 divided by 12 = 186000 rpms...big difference huh?

Now we're not done, you mentioned tumbling. I'll mention it in a human body. Does the current heavy military 5.56 ammo shot out of 1 in 7 twist do more damage then the old 55 gr Nam shot out of the older 1 in 12 twist, to human flesh? If you guys were to ask me you'd all agree I'd say yes, knowing my arguement in this thread. Well it doesn't. In fact what would do more damage is to shoot that heavier bullet in the wrong twist M16 which is 1 in 12. Why? Well because the 1 in 12 doesn't stablelize that heavy bullet and it's yawing in flight so when it hits flesh it tumbles and that sir does alot of damage. In fact the Russian develope their 5.45x39 with a special bullet designed to tumble in flesh.

My varmints are getting more damage because my bullets are near self destruction because of the high spin.

Hope that explains it.

Joe

Art....the jug

http://www.hunt101.com/watermark.php?file=500/7385milkjug.JPG

[Pilgrim]

There was a lot of falderol written in the press during the Vietnam experience and it was usually directed at defending the US of A 5.56 cartridge choice. If my aged mind remembers correctly, the speculation was re: bullet tumbling. I suspect a bullet might tumble if it hits something solid (like a major bone) that causes severe bullet deformation, but seriously doubt it will tumble otherwise, as long as it is sufficiently stable to begin with. The bullet is spun to provide stabilization, remember? It's still spinning when it hits something, so unless the bullet is sufficiently deformed to cause it to become gyroscopically unstable, it ain't going to tumble. Even "solids" shot into buffalo and the like bend or rivet (if not properly constructed) and those bullets might veer off line of sight (so to speak) but they don't tumble to the best of my knowledge. If a bullet is barely stabilized (perhaps like a 60+ gr bullet in a 14 twist barrel), then nearly anything will cause it to become unstable, including twigs, grass, skin, etc. I don't recall the early twist used in the M-16, but suspect the heavier bullets were barely stable when used in those rifles and in that case the bullets would very likely tumble when they hit anything. I believe that is why the Army fairly quickly went to fast twist barrels. Anyway, we are mixing some physics here, I think. The behavior of "solid" projectiles (or FMJ bullets which are pointed solids) is not the same as the behavior of frangible projectiles (like varmint bullets).

The reason varmint bullets are usually sold with a manufacturers recommendation re: upper velocity limits, is due to the bullet jacket ability to resist the centrifugal forces placed upon it by the spin imparted to it. If you shoot the same bullet out of a .223 fast twist (AR type rifle) and one from a standard sporter (14 twist usually, with more going to a 12 twist lately) the AR bullet will be closer to disintegration than the "sporter" bullet because it is spun much much faster. Similarly, if you shoot the same bullet out of a .223 vs. a .220 Swift, the bullet can survive the centrifugal forces from the .223 spin, but not the increased spin caused by the higher velocity produced by the Swift. When bullets go "poof" heading down range, it is due to the bullet disintegrating from the spin. If a bullet is spinning like crazy, and is close to its plastic limit, and then hits anything it's going to come apart. That's what varmint bullets do and why they do it. The lead inside the jacket is still solid to the best of my knowledge, but without the jacket to support it, it too comes unglued at the high rotational velocities and disassembles itself. I'm not going to go to the trouble of calculating the amount of time it would take for a bullet core to become molten, but the specific heat of the material, the friction of the air on the bullet (both spin and linear) will heat the bullet, but I don't think the rate of heatup is fast enough for the bullet core to become molten. It will sure enough get hot, and the hotter lead gets the weaker it gets, so again if anything upsets the bullet jacket, the core is sure to come unglued, so to speak. If you doubt this, then consider a bonded bullet (FLGC with the core bonded to the jacket) for example. It hits critters, and the bullet upsets/expands. After everything comes to rest, the lead is still attached to the jacket, it's just turned inside out. If ithe bullet core was molten, it'd be gone, not attached. Anyway..FWIW...Pilgrim

[StarMetal]

Pilgrim

You may be the expert on spin and stuff but you're not on military bullets tumbling in flesh. Let's go back to Vietnam. The first M16's were really full auto AR15's....and they had 1 in 14 twists!!!!! Yeah, if you can find one, or if you can find proof of that twist, I can direct you to becoming a famous person and maybe some money. So...they found out right away from the Air Force doing target shooting, especially in colder weather, that those little spitzer boattailed bullets weren't getting stablized good by examining bullet holes in the targer that weren't exactly round. This got pointed out and got corrected fast with the 1 in 12 twist.

Okay...it's a fact that boattail bullets don't go through flesh and stay on course as well as flatbase. Surely such an Einstein caliber of person as yourself have heard and read this, and also from post mortums on both animals and humans. Next, the Russians build that bullet of their to tumble faster in flesh, it has a hollow in the nose area to cause it do this. The military noticed right away when they went from roundnose flat based bullet to spitzers with boattails that they started tumbling in flesh.

What you said about the very high rotational spin of bullets making them come apart easily when hitting an animal or something and even in flight sometimes IS exactly what the agrument was about in this thread all along. Buckshot said that a bullet fired from a 1 in 10 only makes one turn in ten inches inside flesh if the flesh happens to be that depth or more...and I got laughed at when I said that is bunk. That bullets are spinning much faster then that.

Now off topic ...God created man equal in his eyes. No matter how educated a man is, or how wealthy a man is, or how prominant.....that all gets left behind when you meet the Lord....it doesn't mean squat. With that said it doesn't mean squat when someone with an education belittles those who didn't acheive as much as they have. So what if some guy is answering the phone at Sierra. You're not better then he is because you got some super duper education. There are alot of people in this world that are brilliant....and without an education. Don't you or Felix give me no horse hockey like "Joe is bitter because he didn't graduate from college" because neither of you know diddly squat about me. I've never said and I never will, I don't brag about an education.

Sorry I had to rant, but you pissed me off.

Oh like I said, I was sorry if I called anyone a dummy. That was wrong.

Joe

[grumble]

When we had a conversation similar to this a few years ago, I think felix applied the term "hoop strength" to the ability of a bullet to withstand the centrifugal forces on it at a high RPM.

A bullet spinning at an RPM that is close to its hoop strength can come apart from almost any force that disrupts its integrity, maybe even just from hitting a mosquito. So yeah, the "exploding" varmit bullets might do it because of their RPM, or maybe because they're designed to come apart lengthwise when they hit something.

But that isn't what this discussion started out as. It was whether the spinning of a bullet as it passed through flesh would cause more damage than a slower spin. The discussion really came alive when (Buckshot, I think) commented that a bullet would only make one or two turns going through a person's body. Turns out he was right on the money.

So, maybe to end the discussion, RPM makes a big difference as to hoop strength of a bullet, but the rotation itself is insignificant as to tissue damage.

[Scrounger]

I don't have the math to do it but it might be interesting to compute the G forces on the jacket of a bullet doing 200,000 RPM versus one doing "only" 100,000 RPM. If it's the same manufactures bullet it would have the same hoop strength and twice the RPMs mighty well cause it to blow.

[onceabull]

Gents: Some of you have already heard more than you ever wanted to know about our youngest Daughter, the "Course Ten" MIT grad.. but I'm not yet ready to give her and Bubba one more"Guess what daddy didn't know" to share with friends,SO-- If I cut a 1/12 twist barrel to produce precisely 12 in.of rifled section,seat a soft bullet against the lands,and drive it forward with a dowel so that it emerges from barrel end 1 Second later.I get one complete turn and 60 rpm. Repeating with new boolit and now driving it to emerge in 1/2 sec.I'm thinking one complete turn,and 120 RM.. Now then,where in this progression is this relationship no longer true ??? only once my boolit leaves the barrel, ?? if so, why ??? and,please, I'm not interested in who can shade who, or who's won who's spurs///// onceabull

[StarMetal]

onceabull,

Congraduations sir, you've seen are knowledgeable of what the rifling and twist does. I would have to say the progression ends at your maximum velocity loading. Like you have found out, and other's haven't, is rpms increase the faster you drive the bullet out of the barrel.

Also what others are stuck on is the rifling twist is just the rifling twists. It's job in to impart spin to the bullet. It's job stops there. That 1 turn in 10 inches, for example, is just for the mechanical dimensions of the rifling in the barrel and applies nowhere else to the bullet, especially when it's down range and/or going through flesh..WHIICH ISN'T one bullet turn in 10 inches. It's only correlation to the bullet beside spin is figuring out the rpms of the bullet in conjunction with the velocity of the bullet.

Joe

[grumble]

You're exactly right, onceabull. After the boolit leaves the muzzle, it will be at that velocity and RPM. All it can do then is slow down in both velocity and spin.

[StarMetal]

Except in outer space Grumble

Joe

[grumble]

"...That 1 turn in 10 inches, for example, is just for the mechanical dimensions of the rifling in the barrel and applies nowhere else to the bullet, especially when it's down range and/or going through flesh..WHIICH ISN'T one bullet turn in 10 inches..."

OK, we're back to square one.

Joe, if the bullet ISN'T going 1 turn to 10 inches, what do you think it IS doing? How many turns in that 10"?

[StarMetal]

It's doing whatever the rpms have slowed down to at whatever the distance is the bullet hit the flesh, then it slows down even more in the flesh. A heck of alot more then 1 turn in 10 though.

Joe

[Pilgrim]

Now I remember why I stopped posting on this board for the most part...Joe - you sure are touchy for somebody who so frequently disparages others. My observation re: Sierra techs had nothing to do with intelligence. It has to do with job opportunites. It has to do with knowledge and the abilty to apply that knowledge to other situations. Period. Quite frankly, I don't give a damn if you graduated from the 8th grade or are post-graduate. Science/math/logic doesn't care either.

For a given bullet spin, bullet stability is based upon bullet length. The longer the bullet, the faster it has to spin to be stable. Bullet style and weight has essentially nothing to do with it. For a bullet that weighs "X", the shortest bullet will be a flatnose/round nose flat base bullet. Spitzer bulllets will be longer; if it is a hollow point it is longer; if it is a boattail it is longer; if it is a hollow point boat tail it will be longer yet; if it has metals other than lead for a core and that metal is less dense than lead, it will be longer. If the military has gone to a boat tail hollow point bullet, then that bullet for any given velocity and rifling twist will be less stable than a flat base bullet. If the twist + bullet + velocity are matched to cause the bullet to be barely stable, then it will tumble when it hits anything. Most .30 caliber rifles are 10 twist, yet some of my benchrest friends are using 17 twist .30 cal. barrels. Why? Because they believe that the less spin you can give a bullet, and still maintain stability, the more accurate the rifle/bullet combination will be. They are launching 135 gr. .30 cal bullets at 2900 to 3000 fps. I am not quite that firm a believer in "over stabilization vs. accuracy", so my bench rifle is a 15 twist barrel for a 135 gr. .308 bullet sent downrange @ ~ 2900 fps velocity. Thus, a 125 gr. .30 cal. bullet (7.62 X 39) that is a hollowpoint boat tail at the velocity of the 7.62 X 39 produces (maybe 2400 fps?), will most likely be marginally stable in any twist slower than 1:14 (best guess without Greenhilll tables in front of me) or thereabouts. That means it will probably tumble when it hits somebody, causing greater bodily injury, and yet will still be within the Geneva Conventions. I suspect this is what the communists had in mind with their AK-47/SKS bullet. We, on the other hand, immediately increased the twist rates of the M-16 when tales of tumbling bullets came out of 'Nam in order to avoid the implications of "inhumane projectiles."

I'm outta here.....Pilgrim

[felix]

Ok, maybe this can help a little. The hubcap. It hit the ground going "how fast"? The hubcap is smaller in circumference than the car wheel, right? Therefore it must speed up to the speed of the car assuming no loss of energy when the hubcap hits the ground. By definition then, someone should be able to come up with the formula to calculate the RPM of the hubcap, given the speed of the car. Also, compute the difference of RPM for an excerise. The final RPM formula for the hubcap should contain the diameter of the car wheel, the diameter of the hubcup, and the linear speed of the car. ... felix

[grumble]

How much more in rotations in that 10", then Joe? Give me a mathmatical relationship.

[felix]

Yep, it is hoop strength is the measure which determines how fast a cylinder, boolit, flywheel can turn before flying apart. Actually, it is the rotational tensil strength of the material. ... felix

[StarMetal]

Fellows...I told someone here I would post a bullet that showed rpms signs or effects. Well I have it here. It's a 115 gr 9mm hollow point fired out of my Browning Hi Power into water. The twist is Buckshot's 1 in 10. I can't remember the velocity, but being they were jacketed I loaded them up to snuff so let's just say 1100 fps. Now with the spin formula we would get 79200 rpms. Okay the first pic is the rear of the bullet as the peddled folded backaround the bullet and you can see they look like a turbine's blade. Next is the side view and the last the nose. Now you tell me, does it look like that bullet only turned one time in every 10 Buckshot inches? in water?

Buckeroo sorry about being so hard on you, but doggone you're the Master of the Silver Stream, should know this stuff. har har har

http://www.hunt101.com/watermark.php?file=500/73859mm.JPG

http://www.hunt101.com/watermark.php?file=500/73859mm1.JPG

http://www.hunt101.com/watermark.php?file=500/73859mm2.JPG

[grumble]

Looks to me like the petals turned about 1/8" in about 1/2" of foreward travel. That's a 1:4 relationship of spin to travel. I don't know what that means in relation to the discussion, though.

Joe, I think what you're trying to say is that a bullet's velocity decreases faster than its RPM. We all agreed to that early on. If so, have we reached consensus?

[StarMetal]

Grumble

It would be hard to work up any kind of formula from the degree the pedals are bent because they hit water. I'm sure harder materials would bend them more, like say flesh. Theirs on doubt an expert could correlate this from examining this bullet, but I sure can't. I posted it to show that bullets are really spinning when they encounter flesh, not just the one turn in the rifling twist.

No, you asked me how many turns the bullet made in the flesh. I said it's hard to tell because 100 yards from the muzzle things have slowed down alot, especially the forward velocity, the rotational velocity not as much, then there's the resistance to the flesh and the expansion to deal with. That's alot of hard figuring.

Joe

[carpetman]

This started out do bullets lose lube in flight? Who cares? The lube is only needed in the barrel and none needed in air.

[StarMetal]

Pilgrim

Stick around. I didn't mean to step on your toes. I didn't say I didn't like you, I just said you po'ed me and you're explaining what you said in a different light, that's fine. You have alot of knowledge and intelligence...backed up with some good education that can be put to good use around here just like in this spin thread. It is kind of funny though that someone who has a background that would know something like this is immediately accepted in his reply. Old Joe couldn't get through to them, perhaps if I was Einsteins brother we wouldn't have had to take this thread that far because the guys would have accept it, because after all then I would have been Einsteins brother. You know what I mean. You'll have to admit, I made alot of people think along with , as you said, disparaging some along the way.

Joe

[grumble]

"...100 yards from the muzzle things have slowed down alot, especially the forward velocity, the rotational velocity not as much, then there's the resistance to the flesh and the expansion to deal with..."

Great! We have agreement. Time to quit. <GGG>

[Scrounger]

Pilgrim

Stick around. I didn't mean to step on your toes. I didn't say I didn't like you, I just said you po'ed me and you're explaining what you said in a different light, that's fine. You have alot of knowledge and intelligence...backed up with some good education that can be put to good use around here just like in this spin thread. It is kind of funny though that someone who has a background that would know something like this is immediately accepted in his reply. Old Joe couldn't get through to them, perhaps if I was Einsteins brother we wouldn't have had to take this thread that far because the guys would have accept it, because after all then I would have been Einsteins brother. You know what I mean. You'll have to admit, I made alot of people think along with , as you said, disparaging some along the way.

Joe

So change your name to "Joe Einstein".... or maybe "StarMetal Dangerfield".

[Scrounger]

"...100 yards from the muzzle things have slowed down alot, especially the forward velocity, the rotational velocity not as much, then there's the resistance to the flesh and the expansion to deal with..."

Great! We have agreement. Time to quit. <GGG>

Arguing with Joe is like arguing with your wife except he can't make you sleep on the couch tonight. [smilie=l:

[StarMetal]

Hey Art,

That stuff was really funny. I got a really good laugh out of it. I'll have to figure out a way to make you fellows sleep on the couch.

Yeah, my brother Al got stuck on that atom thingy. I kept telling him to work on a time machine. We wouldn't be in Iraq if he had left the atom alone. Oh well, I'm sure Adolf would have found someone to do it though.

Joe

[45 2.1]

Felix-

The tire and the hubcap are going at the same RPM until they seperate, Rotational velocity differs at the edge of each, but RPMs are the same.

[felix]

Bob, compute the rpm of the hubcap after it falls off of the tire. Ignore friction at moment of falloff onto the ground, and assume equivalent inertia in the hubcap as before falling off of the car. ... felix

[45 2.1]

Bob, compute the rpm of the hubcap after it falls off of the tire. Ignore friction at moment of falloff onto the ground, and assume equivalent inertia in the hubcap as before falling off of the car. ... felix

To many unknowns there, but without friction of any kind (air, friction with another body etc.) and the same inertia, I don't believe that the thing is going to slow down, it actually might speed up, that is with no friction. An ideal situation which doesn't happen with real conditions.

[StarMetal]

Felix,

I know a guy that was truck driver and one of his wheels came off. He didn't know it till it went past him. My best friend was in a pickup truck behind him and they both hac CB radios on and the trucker drive began singing: "You picked a fine time to leave me loose wheel....." My friend said he nearly wrecked from laughing so hard. I thought it was funny too. But how could that wheel pass him up?

You know, these things we speak of here remind me of the ones for example: A train is doing 60 mph . You are standing on a car way up front and another guy is on the caboose. He has a handgun that shoots a bullet at 60 mph and fires at you. Will the bullet hit you....assuming his aim is good? Another is a fighter plane has machineguns that fire their bullets at 2700 fps, and lets say the plane flys at that speed. How do the bullets even leave the barrel? I know the answers to these but not saying. Putting them here for you fellows to mess with.

I Starmetal, of Cast Boolit Forum, so do solemnly swear, that I will not call you a dummie if you don't know the answer, so help me, Deputy Al strike me down.

Joe

[MTWeatherman]

You know, these things we speak of here remind me of the ones for example: A train is doing 60 mph . You are standing on a car way up front and another guy is on the caboose. He has a handgun that shoots a bullet at 60 mph and fires at you. Will the bullet hit you....assuming his aim is good? Another is a fighter plane has machineguns that fire their bullets at 2700 fps, and lets say the plane flys at that speed. How do the bullets even leave the barrel? I know the answers to these but not saying. Putting them here for you fellows to mess with.

Joe

The answer to the first is....assuming the train is relatively short, yes. The second one...easily.

The velocity is relative to the gun barrel. In the first case the gun is already going 60 mph so the bullet velocity is 120 mph. Unlesss the train is so long that the air friction slows the bullet too much for the bullet to reach the car (there is a limit how far a bullet at 120mph will travel), the bullet will hit you.

In the second case the machine gun is going 2700 fps...the machine gun will fire at 2700 fps relative to the machine gun...or 5400 fps. No problem exiting the barrel.

[floodgate]

Pilgrim:

Working from 74-year old memory here, so not absolutely sure, but I seem to recall some experiments with thin-jacketed, extra-high velocity bullets by Frank Mann or one of his colleagues in the early 1900's, in which several tiny holes were drilled in the sides of the jacket, evenly spaced, and the bullets were fired through paper screens at relatively short range. The bullet prints showed radial streaks of lead surrounding the hole, which was attributed to melting of a layer just inside the jacket due to heating from bore friction(?). I don't recall any comment on what thebores looked like after firing. At least one manufacturer in the 1920's advertised using an insulating layer of paper(?) between jacket and core to prevent this happening. Again, no report on whether it helped or not. FWIW.

floodgate

[Rick N Bama]

This started out do bullets lose lube in flight? Who cares? The lube is only needed in the barrel and none needed in air.

Well it actually started out with me asking about how much lube to use on a Loverin type boolit.

:lovebooli ?

Rick

[Blackwater]

Well, this has been a very interesting thread, not to mention the confusion part! [smilie=l:

As to the comments on the early AR-15's and the 55 gr. FMCBT's: Stoner was given the original concept of a shorter and lighter selective fire auto of small caliber. He rightly reasoned that going to a small caliber high velocity bullet would decrease stopping effect, all else being equal. The "equalizer" that he came up with was to make that little speedy bullet nearly unstable, and thus, it WOULD tumble when hitting flesh or any resistance, or would USUALLY do so. That was incorporated into his original DESIGN. I can't remember whether any except maybe a few original toolroom jobs actually GOT that early 1:14" twist, but I believe that when they found it wasn't as accurate as they wanted (an intentional sacrifice to increase its close range stopping effect obtained by the slower twist's marginal bullet stability), the military VERY quickly demanded the faster 12" twist so they could HIT something more reliably, even at the cost of lessening the original loading's stopping effect.

That whole affair was so clouded by so many "special interest's" allegations, that I suspect few will ever REALLY know the truth. Stoner went on record saying the faster twist would reduce the small caliber's terminal effect. Basically, he and the military had two divergent images of the purpose and utility of the AR-15/M-16. Ain't a thing new about THAT when it comes to supplying the gov't, and particularly with supplying the military with their mainmost weapon.

As to faster twists doing more damage to game when hit, this has been observed for a long time. For instance, the old 7x57 with the early 175 gr. RNSP's were highly touted. The fast twist of the bullets help them open up more quickly, and the reason is as cited by several here, including Star Metal, that the rate of rotation is ONE of the primary factors that helps any bullet expand upon impact.

Bullets have to be a compromise and balance of a number of factors. Any bullet, jacketed or cast, has to be "hard" enough to take the initial acceleration of ignition and the powder burn, to engage and not "slip" the rifling, and to withstand the air resistance upon exiting the muzzle. Faster rotational speeds simply help the bullet "fly apart" quicker, and at lower velocity. Fire the same bullet at the same velocity through a faster twist barrel, and its tendency to fly apart on impact is increased. Simple. The higher RPM's make the heavy lead WANT to fly off. All metals have just so much ability to retain their integrity, and lead is pretty soft, and the most likely metal to fly to pieces due to ANY "slinging off" factor.

Jacketed bullets also have a mostly molten or nearly molten core, as I understand it, and it really doesn't take a lot to make one fly apart. Military FMJ's have pretty thick jackets so that they'll penetrate better - always a desirable trait in military operations where the soldier may have to shoot through something to hit his intended target. Even the thick jacketed military FMJ's, though, have limits. Jackets may be thicker, but that only moves the threshold of "breakup" a bit higher. It does NOT eliminate it. Fire one 6000 fps in a 7" twist barrel, and I bet none hit the target, but will disappear in a blue mist on the way to the target. This is like a meteor breaking up as it enters earth's atmosphere ... or at least sort'a like that.

Now as to those turbine shaped petals on the 9mm., someone along this way (sorry, but forget who at this point, but it IS, I think, an important and mostly glossed over factor in all this discussion) commented that just as the RPM's don't slow nearly as fast as the forward velocity does, as the bullet goes through the air, so ALSO do the RPM's remain MORE consistent after the bullet HITS the target. Same principle, different place along the bullet's flight.

Thus, as a number of folks have noted throughout handgunning's history, the 9mm's fast twist tends to help JHP's open up effectively and consistently, when compared to slower twist calibers and barrels of even faster velocity, like the .38 Super, for instance. This was thought strange at first, and some who didn't really look into the physics of it attributed this to some pretty mystical and vague factors. Others realized that twist DOES affect the "hoop strength," or whatever you want to call it, of any and all bullets. The 7x57 for instance, had a fast twist due to the original bullet's having been 175 gr. which REQUIRED a fast twist. Switching to the lighter PSP's with that same fast twist gave expansion that exceeded many's expectations, who'd only looked at velocity as the criterion by which to surmise a bullet's projected performance. Again, this mystified many initially, who simply didn't look into the matter deeply or thoughtfully enough.

So, in the long term of our beloved shooting sports, it's long been noted that certain calibers with fast twist barrels DO tend to make the bullet expand more violently than other more "normal" setups do.

I'd never really thought about it very deeply, and just noted it in the files of my cobweb covered gray matter. Seemed logical, so no further investigation was pursued.

(Well, I've done it again! Gone too long. Cont'd below:)

[Blackwater]

Continuation:

Now, along comes this guy (whoever you are, and sorry I can't give you credit here - speak up, will ya', and receive my accolades, please) who states that it's because the RPM's don't slow down, even in flesh, as much as the forward speed does. This explains a lot, doesn't it?

RPM's are based on two factors - RATE of rotation, and the TIME those rotations have to conduct themselves. Therefore, if a bullet spinning 120,000 RPM at impact, and is going 2,000 fps at impact, when it hits, it'll be SEVERELY slowed down in its forward velocity. This is clear. What's not quite so clear is just how quickly the ROTATIONAL aspect of the bullet will be slowed. Surely, I think, the bullet CAN'T rotate at full impact RPM's, due to the bullet's contact with flesh creating severe friction, and thus slowing the RPM's significantly and very quickly. However, I think the RPM's at this point, as in air, don't slow nearly as quickly as the forward velocity. Thus, if the bullet's forward velocity is decreased by a factor of "10", let's say, the rotation may only be slowed by a factor of "5," and thus the bullet MAY actually spin more quickly per foot in flesh at impact than one would initially expect.

Is any of this making sense to anyone, and I need a reality check on this. I'm getting over a really bad and persistent darned cold, and the ol' gray matter ain't exactly perkin' on all 8 cylinders. But then, ballistics has always been able to make my head hurt. :violin: ;-)

Also, don't vectors come into play here, and that'll mean calculus, which I never DID really "get" back in college. One day maybe I'll go back, and learn it just to prove to myself I CAN?

[grumble]

I recall, as a high school kid, my dad telling me how, when he was my age, people used to think that if an airplane went supersonic, people couldn't talk to each other because the sound would be lost due to the speed of the airplane.

Joe's brother, Al Einstein, settled that for us with one word: relitivity. [No, Jump, that doesn't mean marrying your brother's sister.] <G>

[Slowpoke]

So, maybe to end the discussion, RPM makes a big difference as to hoop strength of a bullet, but the rotation itself is insignificant as to tissue damage.

You think the same would apply to a hard target, like steel?

good luck

[grumble]

Slowpoke, you have to kinda imagine what the bullet "feels" as it hits something.

Think of something spinning real fast and not going anywhere, like maybe a Dremel tool. You can pinch it with your fingers and almost make it stop, even with the motor on. Imagine jamming that dremel tool into a steel plate -- it will stop very quickly, but it WILL still turn a little bit, even if just a fraction of a revolution.

The majority of the energy in a bullet is in its forward momentum, so in comparison, the rotational energy of a bullet is almost insignificant.

As a sidenote, I once saw pictures of the Inertial Navigation Unit of an aircraft, disassembled after a crash. The navigation gyros were maybe 3/4" in diameter, and they spin at about 200k RPM. The investigators proved the nav unit was working at the time of the crash because of a small teardrop mark in the shaft of one gyro, indicating that the bearing drove into the shaft during the crash, and that the gyro must have been turning at the time. Had it NOT been turning, the bearing would have left a circular indentation, not the teardrop shape.

So, the rotational forces are there, without a doubt. How significant they are is up for more discussion (if we can stand it! <GGG>)

[Pilgrim]

I've heard and read about the melted core in jacketed bullets myself. I used to think it was probably true, too, but I don't any longer. As I mentioned in an earlier post, if the cores were molten, then they wouldn't stay connected with the jacket upon impact. Cores that do not have an enclosed base seem to stay with the jacket as well, assuming the whole shebang doesn't fall apart, and if it was molten it would at least start to run our of the bullet base. I don't recall ever seeing or reading of such a thing. I know from personal experience that bullet jackets get plenty hot as I've picked them up too soon after firing. I also put them back where I got them even faster. I suspect that the bullets with the holes drilled in the sides actually "oozed" lead or the lead was slung out of the bullet through the holes due to the centiripital forces. Did the bullet get hot enough to melt the core? Probably not, but the strength of the lead would tend to go towards zero the hotter it got and with no jacket to hold it inside, the lead would escape through the holes. JMO... I don't have a shred of empirical evidence to back it up though....Pilgrim

[carpetman]

I use to have that problem of my .243 hitting flesh and start spinning but not moving forward. I'd have to get my friend with a 30-06 to come tow it out. I now use 4 wheel drive bullets and don't have that problem.

[StarMetal]

Some people have shot cast to the velocity of jacketed and never heard anything about those melting. Would most the heat come from the friction of the jacket going down the bore? That's what I think. Maybe cast doesn't create as much friction thus not as much heat. There is alot of force in centrifical force. I read where the limitations on jet engines now are the materials of the rotors being able to withstand both the heat and centrifical forces imposed on them.

On the bullet spin slowing down slower then the forward velocity when hitting flesh, I think everything in the bullet comes to a pretty fast end, that is if it expended most it's energy inside the body. Make one wonder thought about the bullet that whizzes through a body with alot of steam left, as to how fast it's still spinning.

Joe

[David R]

OK, I read up to page 4 today. More tomorrow if I can keep up. I never thought of the rotational force acting on game or even cutting a nice clean hole in paper.

One pet peeve of mine is RPMS . Its RPM.......Revelutions Per Minute. There are no RPMS. Two thousand revelutions per minutes?

Good reading, good discussion, I am learning from this

Thanks to all

David

[carpetman]

only sign I know about of being able to detect rotational force is with arrows. If you shoot an arrow into a tight butt(no sexual inuendo)with right hand fletch or with left hand fletch--one will tighten the point and other will make it loosen.

[Four Fingers of Death]

I would think that any lube in grooves would be spun off as soon as the boolit exited the muzzle. Heck, most lubes will stick to your finger as you put them down. This would not be a problem with (dare I say it?) Lee Liquid Alox.

[carpetman]

This arrow that I mentioned that the point is suddenly stopped by the target butt and the point becomes loose-------if it were off the charts in rpm it would completely unscrew---that doesn't happen.

[Bret4207]

Re- the 6.5 boolits bending. IMHO imbalances within the boolit, voids for instance, would be magnified at higher rotational forcce and would be more likely to cause the boolit to "bend". As for the rest, I don't care to venture an opinion.

[grumble]

:...As for the rest, I don't care to venture an opinion."

Aww, c'mon Bret. Let us suck you into this quagmire too! Most of the rest of us admit right up front that we're "dummies." Join the crowd! <GGG>

[StarMetal]

Tpr Bret,

We know the Jarheads know all kind of stuff about 6.5...after all they fought enough Japs that used 6.5 along with their 7.7's..to give the Marines a very knowledgeable base on 6.5 characteristics. So quit holding back on us and spill the beans. Tell us about those secrets of the Marines finding all kind of bend 6.5 Jap bullets on Iwo Jima and Okinawa.

Tpr Bret, the thing that throws me off on the 6.5 is I shot some really long heavy cast bullets out of my AR15 with the 1 in 7 twist which is pretty dang close to that Swede 6.5 twist and I shot that really really up there in velocity, say around 3000 fps. I won't lie and say they shot good but let me tell you that I could hit a man at 100 yards with them. So what got me is that they didn't do that thing Waksupi says...shoot off to God knows where. So that's telling me they aren't bending in my rifle.

Joe

[slughammer]

One pet peeve of mine is RPMS . Its RPM.......Revelutions Per Minute. There are no RPMS. Two thousand revelutions per minutes?


If RPM is allready plural, how do we use RPM for values 0 thru 1?

[felix]

Not only bending is possible, but flying apart as well. Remember the hoop strength of lead. There's much more outward force on a bigger diameter boolit at the same RPM. ... felix

[StarMetal]

That's true about the bigger diameter but I think my 3400 fps made up for that. I really don't think Waksupi or whoever was shooting them was getting anyways near 3400 fps with the 6.5 Swede. Not saying that can't be done I just don't think they loaded it that fast.

Joe

[Bret4207]

Well Joe, I don't want to start a war- AGAIN! But, while I haven't done anything much with anything under 25 cal, 30 and over mostly, I have read a bunch of articles in "The Art of Bullet Casting" and some other books or articles from Handloader that discuss the smaller cal booolits. After reading them it seems to me it could be it's combination of the smaller diameter, shorter boolit and a plain diffrerent rifling DESIGN that makes it happen. Now before you take off on the similar twist idea, stop and think for a sec. ALL the Swedes have the same basic style and pitch of rifling IIRC. Your 1/7 .22 is a different style in some respects I'll bet. Maybe it's a different groove style or the profile is otherwise different. Plus that 6.5 Swede has a loooong throat, even in comparison to a long throat 22. I'm betting it's mostly the bore size and a relativley shorter boolit. A shorter boolit design is going to stabilize easler than a longer one, although we do wonder about "over stabilation". And there's the possibilty some barrels are just more cast freindly than others. Buckshot spoke of getting good accuracy from the Swede with a holler pointed 130ish gr Lovely Loverin (That he SOLD!!!) I mentioned before the possibility of using a hollow pointer and trying some of the more difficult designs to see if it helped. Maybe it would help the 6.5.

The other possibility is that some shooters and cast reloaders are just "gifted". After all, I have never heard of anyone else anywhere getting half inch groups with an SKS or even in a bolt gun chambered for the same round with jacketed, much less cast. Maybe you just have a lot more time to put into than the rest of us and lucked into a couple of special guns, boolits and loads.

[Bret4207]

BTW- I knew a WW2 vet who got hit with a 6.5 round right above the left nipple. He delighted in showing the scar, generally in public places most folks would try and remain dressed. He'd either pull his sweatshirt right off or unbutton his shirt and show it off., even if you'd seen it 100 times before. The scar was probably the most attractive part of his body if you take my drift. Yeeeesh!

[StarMetal]

Tpr Bret,

Not war comrade. Hey my AR15 got more then a long throat, it's the darm Holland Tunnel. That 70 gr bullet is pretty darn long. I dunno but that Swede. It's like my one good friend thinks the 44 mag kicks because that bore size must be perfect for good recoil conditions.

About the SKS...now remember, I said I CAN NOT shoot consistant 1/2 inch groups. Now again for the work. First it's a Yugo SKS, they are brute strong and heavy. No stamped parts. The barrel is threaded into the receiver. I glass bedded the receiver and first inch of the barrel. I took off the grenade laucher sights, the bayonet (even cut the lug for the bayonet off) ditched the cleaning rod, and cut down the muzzle fixture for the grenade. Then I scoped it. I'm neck sizing the brass and I'm using heavier aluminum gaschecks that I make myself. The only things I haven't done are weigh the bullets and seat into the rifling. I'm not sure I can seat that Lee 312-155 into the rifle as most that bullet is bore rider for one and for two the groove bands on it are very short and if the bullet has to move out very far to touch the rifling I"m not sure anything will be left to seat in the case. I'll have to check the throat on and see how much distance I have to play with as I have thought about seating out farther. Another option is to try some of my other bullets like the 314299 and 311284. You'll notice I don't have very many lightweight bullets in any of my caliber...I've always liked and shot the heavier. My other attempt will involve reducing the powder loads and see what that does. Don't forget this load I'm shooting is blistering. The 4895 I'm using comes all the way up into the neck half ways.

Joe

[Bret4207]

Ok- just re-read this whole thing. Stand by boys-

1. Joe- your picture. My vivid imagination says that bullet made a little more than maybe 3/4 turn for that bend. How far into the water did it travel to make that 3/4 or even 360 degree turn? Who knows. In water I'd say not too far since a liquid can't compress and it would slow that bullet down real fast. Flesh would do different. Anything beyond that is a WAG.

2. On the rpm vs twist- As I understand it the faster you push a bullet the faster the rpm. But since the bullet is covering the linear distance at a faster rate, isn't the twist rate the same? In other words if a bullet is launched from a 1/10" twist it isn't going to hit the target at 1/7". I can see the rpm dropping slower than linear speed, but I can't see the rotation lasting for a relatively long period of time. The energy dump from hitting the target and/if expanding has got to be huge realtively speaking. There's also the so called "hydro-static" effect of the higher velocity bullet to be considered. A flat faced bullet causes more damage allegedly due to the fluid damage to tissue. Velocity is reputed to do the same thing even with a spire point and no expansion. Interesting, but the math is way past me.

3. Doesn't the tire that comes off the truck pickup some speed due to the tires kinetic energy causing the tire to accelerate slightly when it's freed of the weight of the hub/brake/etc?

4. The SKS- Couldn't care less. I have a couple guns that will shoot 1/2" groups on occasion. What makes you think you didn't flinch a bit and throw the boolit headed out of the group into the group? Give me 10-10 shot groups and lets see the aggregate and then you'll know if you have a sweetheart load and gun. If it's really that good you should be competing in the postal matches.

5. Didn't realize you were using a 70 gr 22 cal bullet. That being said I would think the answer might be found by using swaged boolits of equal alloy in the same type rifling to eliminate any possible voids in both 22 and 6.5. Beyond that if the two boolits are spinning at the same rpm, isn't the surface speed of the larger diameter boolit actually faster than the smaller diameter one? Might have that backwards. If I'm correct then maybe were getting into hoop strength again.

6. Wish I had a gift for math.

6. As for your apology Joe- we all need to try and keep the red rage from making us say unfourtunate things. Getting the whole family po'd just makes life miserable for everyone.

[Blackwater]

Carpetman, you simply MUST let me buy one'a them 4-wheel drive bullets! I had to clean my screen to see to type this post in! Thanks! [smilie=l:

Re the molten cores, I've chased a few bullets, but never been able to run one down. I have, though, seen the blue steaks before hitting the target, and seen the targets both blank, and looking like they had been hit with a load of shot, with gray mist around each tiny hole. Cores CAN go molten, but not typically, as with most game bullets. Hornet bullets in a .22/.250 will often "blow up" in the air, and the gray mists that pepper the target and surround each tiny fragment's hole are an indication, I think, that at least SOME of the core goes molten under THOSE conditions. Not always, but under those conditions..

I'm no ballistician, but I think I know enough that jives with the physical and theoretical science that I do know, to know that it's not quite as cut and dried as it seems. Thus my interest in this thread. Always open to learning something new, and when I've posted, it's more thinking aloud than anything else, which I think is 90% of what we've got here. Nothin' wrong with that at all, either! That's how I've learned most of what I know, and think I know. Much of what I "know" is simply what I've accepted until something new comes along to illustrate further, to disprove it, or modify it, that simply jives with what I do know on a more concrete basis. I guess that's all any of us can really do.

I'll tell you one thing, though, this thread has caused me to think harder than I have in a long time about what all influences a bullet along its path through the air and into flesh, and that is a GOOD thing, IMO.

I'm beginning to get at least a better "feel" for it, I think, which essentially means I'm more confused than I was at first. Unfortunately, this usually preceeds REAL learning - a fact that's frustrated me before, and I don't think I'm alone here in that???

At any rate, Star Metal, you've strained my brain, and I think I've got to go pour up an adult beverage now. THANKS! ;-)

I think at least some of the confusion here, and maybe the dissention too, is that some of this depends on certain circumstances peculiar to certain situations, and cannot be overly generalized to all circumstances or instances. Does that mean I'm starting to understand something, or should I just go pour a double up???

[waksupi]

Joe, keep in mind the bullets that were bending on me, were a batch of pure tin bullets, sent to me for high speed testing, here at the Rocky Mountain Ballistics Laboratory. They were not lead bullets.

[floodgate]

Pilgrim:

I THINK the speculation on those early experiments was that only a shallow surface layer of the lead just under the (very thin) jacket was melting, or at least softening. Lead's thermal conductivity is not all that high, and I, too, doubt that any substantial part of the core was molten. But SOMETHING was happening just under the jacket.

I dug out my old physics textbook last night and tried to calculate the kinetic energy of rotation (only) as compared with the K.E. of translation (i.e., forward motion, the energy figuure we usually use) for a .30 caliber bullet at 2500 fps from a 1 in 10" barrel. I did it twice: once I got the result that almost as much energy is bound up in bullet spin as in its forward motion; the second time, I got about 1% of the energy in spin, 99% in forward motion. (I'm not the mathematician I once was, if I ever was!). Sooo.... I will testify for whichever side offers me the best deal on the Ideal moulds #311329 or #311284 I am looking for.

floodgate

[StarMetal]

Wow! Lot of stuff here.

Blackwater...I'm glad you learned something...and it's not confusing to you. The higher the rpm of a bullet the wee little bit more energy it has and if the spin is close to it's strutural strenght distruction then the more it's going to come apart hitting something. For varmints that's good, but I would surmise for anything else bigger, maybe not.

Tpr Bret,

I almost have that sweetspot on that SKS. The sweetspot will be where it will shoot that group consistantly time after time. I wanted to say along time ago I would have never believed a semi-auto rifle would ever shoot alongside or outshoot a bolt rifle. Well they will. In fact mike from co will tell you how good an AR10 in 308 will shoot. There are alot of others too, the SR25 Stoner, and some special sniper HK to name a few. Anyways point being just because it's commine semi-auto SKS design doesn't mean it can't be made to shoot exceptional.

Bret, the twist rate has nothing to do with what the bullet is doing once free of the barrel, only except to be involved in the formula to figure out the rpm of the bullet. The twist of rifle is only the means to spin the bullet, so get it out of your head for anything else.

I got hosed down pretty good with that water when I shot that 9mm and I was standing about 10-15 feet away. Good thing it was a summer day. It went through quite a few water bags, but can't remember the distance and count now.

Waksupi
My God! Pure tin!!! One question...how will I say this...hmmm.. did they tin up the bore? hahahahahaha. One other thing too Ric, what's to say that snow bank didn't bend them? That would be an interesting test in itself, shooting into a giant snowbank that when it melts you can find the bullets. I know your thinking here buddy and that is being of very little resistance the snow slowed the bullet down gently and it didn't deform any. Sure would like to know thought.

Well it's good that alot of folks got to blow the carbon out of their thinking process.

[Buckshot]

Well it actually started out with me asking about how much lube to use on a Loverin type boolit.

:lovebooli ?

Rick

.........Probably about half. I was also hoping to answer the question as to why we sometimes recover boolits at 50 or 100 yards and they still ahve lube on the slugs.

http://www.fototime.com/3870C943F75D6DF/standard.jpg
These are Lyman 7mm 150gr Loverins. Lube is Javalina. I've shot them from a couple 7x57's at 2450 fps without leading. At 50 yards they group a bit over 1" for 5 rounds.

......................Buckshot

[Frank46]

Now I know why my high school teacher told me to take algebra, except I didn't take to it. I'm going to take a couple asprins and lay down, I've got a headache. Frank

[Bret4207]

Re- Twist rate- Joe said smething like "the twist has nothing to do with the bullet once it leaves the barrel". Well, someone please clear this up in laymans terms once and for all then. Regardless of velocity a bullet can't GAIN rotational speed outside the muzzle can it?

On the lube, (Oh were we talking about lube?), what happened to the "Lube is a liquid under pressure no matter how hard it is" theory? For that matter, if the bullet core is taking enought heat to melt, (don't buy that one yet), then why isn't the lube melting and coming off in flight? We had a long thread on Shooter or Aimo about this and I wish I could access it.

Joe- I know there are some exceptional semi-auto platforms out there. Just never saw an SKS do it. You HAVE to eneter the postal matches. What a sleeper!

[StarMetal]

Tpr Bret,

Let's take that 1 in 10 twist in a 30-06. Say you have a cast load that shoots the bullet to 2000 fps. Doesn't matter what the weight is for the formula. To figure the spin you multiply 720 time the velocity of 2000 and divide by the twist rate of 10. That gives you the rpm. So you fire the rifle, bullet exists the muzzle and now WE'RE DONE WITH THE 1 IN 10 TWIST. Kinda just like booster rockets on a missile. Once launched their job is done. The twist spun the bullet and also figured in the formula. The bullet is spinning away at 144000 rpm. That's it.

You make my SKS sound like an old ratty looking Chevy cheap model Biscayne, but the baby has big block super engine in it...a SLEEPER. I don't know Bret, maybe it is maybe it isn't. I've been saying all along those Yugo SKS are good ones. Robustly build and all machined. Plus I've done alot of work on it. I'm thinking about picking up one of the cheaper shooter grade ones and rebarreling it to 7x39. I imagine that round exists, but I'd like to have an SKS in that caliber. I thought too the thing might make a nice 44 mag or 45 Long Colt too. No no no Buckshot, I don't think we can make it a 45-70....maybe a 45-70 Short though.

Joe

[Bret4207]

Math ain't my best subject, bear with me. I understand the rpms increase with velocity, got that. But the linear speed is also increased with velocity, so the "twist" or rpm for foot traveled should be the same, right? Regardless of the velocity, are you saying the bullet no longer revolves 1 time in 10" if fired from a 1/10 twist? If so, what causes the change? If anything it should slow due to friction, etc. I've re-read this thread several times. I just don't see how an object can gain many rpm once it leaves the muzzle. There's nothing to push it or cause it to rotate any faster is there? It's not like the tire coming off the truck that's freed of the brake drum, etc. The max rpm should be as it leaves the muzzle. The rpm will drop as the bullet trravels, though probably not at the same rate as the linear speed.

Whutnell am I missing?

[StarMetal]

Tpr Bret,

Bearing with you here. I thought of what you just said before. I was wondering if the bullets forward velocity is so fast that and the bullet is spinning so fast, if it was possible the bullet could turn that many rpm within that 10 inch distance. For the answer to that I'm afraid we need the services of Pilgrim because I will admit up front that is beyond my math too.

At any rate say it did, my GOD!!! Bullets go through hell don't they.

Joe

[felix]

Bret, you are missing nothin'. ... felix

[StarMetal]

Felix,

Well explain it sir, with the math and formulas

Joe

[felix]

Joe, it has already been done somewhere in this thread or one like it, at least I think so. ... felix

[44man]

I have a lot of trouble with the arrow heads coming loose also. By experimenting with the problem I tracked it down to the inertia of the head to resist the initial turning of the arrow at release, NOT stopping it's turn in the target. Targets will stop the rotation of the whole arrow fast because of the slow spin to start with and the friction of so much shaft in contact.

[carpetman]

44man--I cant buy the theory(although it may be correct)that the arrow point is coming loose at release. The point and the arrow are both turning at same speed and unless something is holding the point,they both turn. Sorta like spinning a nut and bolt and unless you hold the nut,it doesn't tighten or loosen. The point of the arrow hitting the target butt is momentarily stopped before the arrow does. Another thing that makes me believe that is when it happens is I had a Stanley Hipps target which is a tight foam and offers more resistance and the problem was worse. Using a target with less resistance like the tow sack with plastic shopping bags and the problem went away. Actually making some thin leather washers fixed it.

[Bret4207]

Ok Felix- so does it work like this?-

A boolit launched from a 1/10" barrel at 2000fps is doing 144,000 rpm or 240 rps (second). It's 100 yards or 3600 inches to the target. Assuming no velocity loss, the bullet takes .15 second to get to the target from the muzzle. 240rps x .15 seconds is 36, which would be 1 revolution in 10".

I think so anyway. If I'm correct, then the twist rate of a given barrel gives the boolit its intial rate of revolution and that rate remains the same minus slowing from friction, etc.

Have I got it?

[Bret4207]

Whoops, transfered it wrong from the work sheet-

2400 rps x .15 = 360 = 1 turn in 10"

Hey, at least it wasn't another gross overload with Red Dot!

[StarMetal]

Well fellows...GULP!....this is a hard post to do. But I'm going to fess up and do it. Read very carefully. I WAS WRONG...did you get that? I'll repeat I WAS WRONG. I should have done the math instead of running my mouth. I apologize to everyone I offended and I especially extend an apology to that doggone mule lover ....the old Buckeroo himself Buckshot. Buckshot Sir, I'm truely sorry. Before I go and hide in the corner here's the figuring I should have done at the start:

Let say the bullet has a velocity of 2000 fps. To convert that to inches we multiply it by 12 which now gives us 24000. The bullet is now traveling in inches per second. Now lets take the spin. We already established it's 144000 rpm. Let's change that to seconds by dividing by 60 which gives us 2400. So in one second the bullet has spun 2400 times. Ok how long does it take the bullet to go 10 inches? We divide 10 inches by the 24000 inches it took the bullet to in one second. This gives us .0004167 of a second for it to go 10 inches. Now to find how many time that bullet turns in .0004167 of a second we multiply that number times the 2400 times it turns in one second which is 1.00008 which is close enough to round off to 1.

Tpr Bret did it in a more rounded off fashion, but still correct. It's still 1 turn in 10 inches.

Anyone else in the corner?

Joe

[onceabull]

All: Someone should call the "laughing guy" at Sierra.... Onceabull

[StarMetal]

Let em roll boys....I surely deserver it.

Joe

[David R]

Going back a few pages, I shot many boolits into the snow. I put targets up and shot all winter. In the spring when the snow was gone they would be in a nice pile in one general area. I could pick em up and melt them down again. Perfect recycling. These boolits looked just like I cast em except for the rifling on them. Most still had the lube. NO damage to the front from the snow. These were cast pretty hard and all 45 cal.

Interesting discussion. I never thought about the damage the spin could do to game or a target.

David

[grumble]

Joe -- how much time could you have saved yourself if you had just read the formula I posted two days ago? <GGG> It did just what you have now figured out for yourself!

But, I still can't explain why a wheel that comes off a semi at highway speeds passes the truck it came off of.

[StarMetal]

Wait a minute guys....there was paper and pencil over here in the corner and I got to thinking again. We all agreed on that the forward velocity diminishes at a faster rate then the rotational spin. Well what's to say when the bullet hits the flesh and slows down, alot, that the rotational spin kinds goes along and spins, but not decreasing at the same amount the forward movement has. Kind of like when you spin one of those little spin toys you got in say a Cracker Jacks box, but you hold it and spin it above the table, then let is go and it drops to the table and continues spinning. Well, the fall to the table is the forward velocity and when it hits the table the thing still keeps spinning. That's what I'm saying about the bullet hitting the flesh. I bet the 1 in 10 turn is disrupted then.

Joe

[StarMetal]

Davidr

Well that pretty much explains it. The snow does slow them down gentlely. I have found 22 rimfire bullets like that in good shape, but never found any centerfire bullets. So Waksupis 6.5 is getting bent somewhere before hitting the snowbank.

Joe

[Scrounger]

Joe -- how much time could you have saved yourself if you had just read the formula I posted two days ago? <GGG> It did just what you have now figured out for yourself!

But, I still can't explain why a wheel that comes off a semi at highway speeds passes the truck it came off of.

I would think the velocity of the car (50 MPH or whatever) would be added to the rotational energy of the hubcap to give it a higher velocity in total. ???

[grumble]

Joe: "I'll repeat I WAS WRONG."

Might you go so far as to say, "dummy?" <GGG>

On your later post of the top spinning on the table. It then does 10 turns in ZERO inches. A bullet won't do that, though, it doesn't have enough rotational energy.

Time for us to start bribing Floodgate for what he computed for that spinning mass.

[grumble]

I dunno, Scrounger. I'm still trying to wrap my mind around the puzzle. And, that's very little material to wrap around something that large!

[MTWeatherman]

In response to the initial question: I have used the Loverin 323470 in an 8mm with half the lubes lubed and works as well as with all of them filled. However, don’t consider that to be much of a testimonial...I’ve never been satisfied with the rifles accuracy but that’s another story.

Talk about a thread being hijacked...and now I’ve become a part of it...for the second time. Bret, your understanding is perfect. I’ve been biting my tongue for two days, but it hurts too much to continue. I well may regret wading into this but here goes:

Sorry about the long post...had to do it in two posts because of word limitiation but don’t see another option to make the point. Here’s my view on the twist, energy, etc. issue.

1. The velocity of the bullet and the rifling rate does indeed determine the rate of bullet rotation but you have to use the same units of measurement to get it correct. A 150 gr bullet traveling down a 30-30 barrel with a 1 in 12 inch twist (or 1 per foot) with a 2400 fps muzzle velocity will indeed leave the muzzle with a rotation of 2400 revolutions per second. At any point in the barrel the linear and rotational velocity will be different as the bullet accelerates. For each foot it travels, it turns once...so 2400 linear feet in one second gives the above result at the muzzle....if it traveled 2400 in one minute would be 2400 RPM. If you want to convert that 30-30 bullet to RPM you must multiply by 60 to get minutes so in reality it would be 144,000 RPM .if that’s your choice of measurement.

2. Once the bullet is out the barrel, all acceleration forces from the expanding powder gases are gone. Its now at its maximum velocity and rotation. The forces now acting on it are air friction to slow both linear and rotational velocity. No acceleration force...only deceleration force. The spin can’t accelerate, it decreases. That’s Newtonian physics (the old F=MA)...if you actually believe that the linear or rotation velocity increases after the force of the powder is gone...you better come up with another force to explain it...otherwise you’ve just come up with the first violation of Newton’s second law of motion in 300 years. Publish a scientific paper...you’ll be famous.

[StarMetal]

Grumble,

Yeah, I'm a dummy in the fact that I didn't do ALL the math first before so passionately agruing. I'm positively sold on that when in flight the bullet does turn whatever it's rifling twist was as far as forward distance, but not sold when it hits flesh. It may spin more then one turn or alot less then one turn when it hits that's flesh. You have to admit that before the bullet comes to a stop in forward motion the spin has to change too, does it change proportional or not is the question I want to know now. That's assuming the bullet maintains a fairly nose forward motion through the flesh.

Joe

[MTWeatherman]

3. The linear velocity slows at a much faster rate than the rotational velocity. We’ll only consider wind resistance here...gravity simply pulls the bullet toward the earth...no it doesn’t serve to accelerate the bullet unless you are shooting at your feet...the force is normally directed perpendicular to the direction of bullet travel. Wind resistance is equal to the square of the velocity increase...double the velocity and wind resistance just went up 4 times (2X2), triple it and velocity just went up times (3X3), etc. Lets take a look at wind friction for rotation...that is the wind resistance on the outside of that bullet as it turns...so what is the velocity of that surface moving through the air? Lets consider the movement of the top edge of one the rifling marks...it has to trace the circumference of the bullet. That is determined by multiplying the bullet diameter times Pi or .308 X 3.14 and that equals .968 inches so, what the hell, lets just call the circumference 1 inch. However, since it is rotating 2400 revolutions per second, it actually is traveling 2400 X 1 inch or 2400 inches per second. Divide that by 12 to get feet and you get 200 fps. So the linear velocity is actually 12 times the rotational velocity and the force of wind resistance to linear motion is 12X12 or 144 times the resistance force to rotation velocity. The wind resistance to rotational force is significantly less than 1% of that to the linear velocity. So, lets just assume that the rotational energy doesn’t change enough to even consider over hunting ranges...at impact the bullet will have lost energy due to its forward motion through the air...but none of its rotational energy.

4. The energy of the bullet is indeed the sum of its linear energy and its rotational energy but the question being batted around here is how much does rotational energy actually contribute. There is a formula for each. Of the two, kinetic energy is the easiest to derive..½ mass times the square of the velocity. No need to calculate by hand....ballistics tables and programs do it too easily to mess with it. At 100 yards that 30-30 bullet will be doing abut 2000 fps with about 1350 foot pounds of energy. However about rotational energy? That’s more complicated...the moment of inertia times the square of the angular momentum. Want to try running that one out? I didn’t. Without going into details, it can be approximated using an easier method and I came up with significantly less than 1% of the linear energy. However, courtesy of Varmint Al’s website, I actually came up with a program to do it for me. The rotational energy value at 100 yards would be 4.33 foot pounds or about .3 % of the linear energy...that result is much more accurate than mine...but in agreement.. That’s not much and it would seem to me that though the “buzz saw” effect would be there it wouldn’t be much and once that bullet hits flesh and expands...that rotation would stop rapidly. Also, keep in mind that the when that bullet expands, the rotational velocity will come down rapidly...the effect of a spinning ice skater extending her arms...move the mass outward the velocity slows. You want that program?...you can find it on his website or let me know and I’ll furnish the link.


Rifle Twist Bullet Bullet Velocity Spin Powder Recoil Bullet Energy
1. Wt Dia Mass Mass Energy Linear Spin
(lb) (T/in) (in ) (Gr) (fps) (rpm) (Gr) (ft-lb) (ft-lb) (ft-lb) Rifle Info
11.5 14 0.224 40 4040 207771 38.7 3.26 1450 1.83 Encore 22-250 Imp/40
11.5 14 0.224 40 4040 207771 3.9 0.89 1450 1.83 Encore with 90% eff. MB
8.0 14 0.224 33 3050 156857 11.5 0.95 682 0.86 Contender 22-K Hornet
9.2 10 0.172 17 2550 183600 9.0 0.25 245 0.36 Contender 17 HMR
8.0 14 0.224 55 3700 190286 40.0 6.08 1672 2.11 Rem 22-250
8.0 10 0.243 100 2900 208800 42.0 9.42 1868 5.44 Sako 243
8.0 10 0.243 100 2900 208800 4.2 3.81 1868 5.44 Sako 243 with 90% eff. MB
8.5 12 0.338 200 3000 180000 73.0 33.20 3997 15.65 Rem 338 Mag
35.0 15 0.510 750 2800 134400 233.0 92.55 13057 74.49 50 BMG
35.0 15 0.510 750 2800 134400 23.3 44.26 13057 74.49 50 BMG with 90% eff. MB


If a rolling tire comes off a vehicle and passes it...Newton’s law still applies. Either a force was present to accelerate that tire(could be gravity if you were going downhill and braking the vehicle) or, more likely, the vehicle decelerated. Look at it this way, the vehicle is moving down the road...you have your foot on the gas to overcome wind resistance. That is accomplished by those rear tires being turned by the force of your vehicles drive train. Lose a tire and the force stops...vehicle has more wind resistance than the tire so immediately slows. The tire however has less wind resistance than the vehicle, so, initially turning at nearly its previous rate, is able to maintain that speed a bit longer than the vehicle...and pass it.

I considered starting a new thread for this one...seems like it belongs there. However, for continuity, didn't. OK guys, have at me.

[grumble]

Joe: "...before the bullet comes to a stop in forward motion the spin has to change too, does it change proportional or not is the question I want to know now..."

That's the same question I was trying to get YOU to answer two days ago! <G> You said there were too many variables to figure it out. I'll give the same answer.

[carpetman]

yea I'm getting tired of shooting deer with a spinning top. Next year going to use a yo-yo. Those darn spinning tops tear up too much meat with all that rotational energy. Back when I just used bullet weight and bullet velocity for figuring energy,everything was fine. Then I started multiplying it out by the rpm and now the deer explode with all that added rotational energy.

[StarMetal]

When objects are at rest in space, they are moving at maximum speed through time and when they are at rest in time, they are moving at maximum speed through space.

[grumble]

MTWeatherman: "If a rolling tire comes off a vehicle and passes it...Newton’s law still applies. Either a force was present to accelerate that tire(could be gravity if you were going downhill and braking the vehicle) or, more likely, the vehicle decelerated. Look at it this way, the vehicle is moving down the road...you have your foot on the gas to overcome wind resistance. That is accomplished by those rear tires being turned by the force of your vehicles drive train. Lose a tire and the force stops...vehicle has more wind resistance than the tire so immediately slows. The tire however has less wind resistance than the vehicle, so, initially turning at nearly its previous rate, is able to maintain that speed a bit longer than the vehicle...and pass it."

Hmm. How can any forces from the truck be imparted to the detached wheel? Regardless of the torque on the wheel, it is still only going at the same number of RPMs (forgive the plural initialism! <G>) as the other wheels. There's no"extra push" given it at the instant it comes off. The only thing that makes the least sense to me is that the weight of the truck will flatten the wheels where they contact the pavement, so once the weight is off the lost wheel, it becomes round again, effectively increasing its diameter and thus able to go faster than it was immediately before coming loose.

But even that doesn't make a lot of sense given the relatively low RPM and the minor change in diameter.

[MTWeatherman]

MTWeatherman: "
Hmm. How can any forces from the truck be imparted to the detached wheel? Regardless of the torque on the wheel, it is still only going at the same number of RPMs (forgive the plural initialism! <G>) as the other wheels. There's no"extra push" given it at the instant it comes off. The only thing that makes the least sense to me is that the weight of the truck will flatten the wheels where they contact the pavement, so once the weight is off the lost wheel, it becomes round again, effectively increasing its diameter and thus able to go faster than it was immediately before coming loose.

But even that doesn't make a lot of sense given the relatively low RPM and the minor change in diameter.

Grumble:
I agree with you...the force from the truck is no longer applied to the wheel once it comes off...and no other force is applied to that wheel. That wheel is rotating at exactly the same speed as the other wheels.

It's what happens at that point that makes the wheel pass you. There is no longer a force applied to the rear wheels to maintain the vehicles speed (a wheels gone).. ..so the vehicle immediately slows due to the wind reisistance. (Since wind resistance increases rapidly with speed, its my bet that the "passing wheel" effect noticeably increases as vehicle speed increases.) There is no longer a force to maintain the loose wheels speed either...but wind resistance is less...enough so that it is now rotating a bit faster than the other wheels attached to the slowing truck. Although it is slowing also, this allows it to gain on the vehicle.

In the case of the flat spot on the tire...that effectively offers more rolling reisistance to the tire. However, once the tire breaks free its loss cannot accelerate the tire...only reduce the rate the tire slows due to friction. It would definitely allow the "passing tire" effect to be more noticeable than if the tire maintained a flat spot. However, any increased diatmeter of the tire couldn't accelerate it. If the diameter of any rotating object is increased while its weight (or mass remains the same) the rate of rotation will slow unless an external force is applied. This is the old cliche of the spinning skater extending her arms...she slows down when they are extended...speeds up when she draws them in.

[carpetman]

The loose tire doesnt speed up the vehicle slows down. Without that tire,there is drag and most folks hit their brake.

[Bret4207]

MT Weatherman- MAkes sense to me, unbelieveably.

Joe- Got some recipies for crow around here someplace. They're good with enough horseradish and sour cream!

[Scrounger]

yea I'm getting tired of shooting deer with a spinning top. Next year going to use a yo-yo. Those darn spinning tops tear up too much meat with all that rotational energy. Back when I just used bullet weight and bullet velocity for figuring energy,everything was fine. Then I started multiplying it out by the rpm and now the deer explode with all that added rotational energy.

SIZE=2]Haven't seen mention of you shooting any deer lately, your grandson is getting them all. I suppose you're specializing in cats these days but haven't seen any cat trophies either...[/SIZE][

[grumble]

MT Wx

Good explanation. I'll have to think about it. I was thinking of a wheel I once saw come off an 18 wheeler's trailer. It was on a fairly flat stretch of 16-lane interstate (Near Thousand Oaks CA, to be exact). This one didn't pass the truck, but it stayed even with it as it went across all 8 lanes at about a 30 degree angle. Had it gone straight, it would have passed the truck. The trucker didn't know what had happened until the excitement began all around him with people trying to avoid the 65 MPH wheel, so I don't think he slowed down until after the wheel was in the median.

A friend of mine thinks that a trailer wheel won't pass the vehicle, but a driven wheel will, because of the elastic properties in the tire itself, springing forward as soon as the load is removed. Kinda like a rubber band.

[StarMetal]

Tpr Bret,

By all means send them on. I'll put some corn out as to lure in some crows. Pm will be fine.

Joe

[Finn45]

What happened to Joe, has happened for me in many occasions. Just too sure about something and not time to really give a thorough thought for it. Nice page count btw.

Well, after this is starting to be yesterdays debate, how about the old and reliable one with released boolits... does it reach immediate consensus here, or...? This is an oldie; one 200 grain .30 cal boolit having BC of .400 is dropped from the table at the same time as two other boolits are launched from a rifle. One launched boolit is .30 cal 180 grains having BC of .300, muzzle velocity 2000fps; other launched boolit is similar to the dropped one, .30 cal 200 grain with BC of .400, muzzle velocity 2500fps. All boolits are dropped/launched from the height of 1 yard from the ground level and rifle barrel is aimed exactly parallel to the ground (zero degree, not aimed high or low). Which of the three boolits will hit the ground level first (1 yard drop) and how far from the ground level the other two would be at that exact time? This should be done so, that all boolits will release at the same time; dropping the first one at the same time as other two releases from the muzzle.

Sorry if my English is lacking with these things... Somebody else should give the explanation for this for that exact reason btw.

Thread hijacking maybe, but it's already done. I have one other in mind, weird one and not firearms related, will see if I recall it or not.

[waksupi]

Another fly in the ointment. When a wheel leaves the vehicle, would the diameter not expand, due to centrifugical force on the tire?

[Finn45]

When a wheel leaves the vehicle, would the diameter not expand, due to centrifugical force on the tire?

Centrifugal force would not be greater because the wheel rotating under the vehicle has the same rpm as the wheel just released? BUT, if the wheel was under certain load under the vehicle which collapsed (?) it a little, then this collapsing would be smaller after releasing (no load) making actual circumference bigger thus causing wheel to accelerate a bit due to bigger circumference? Same rpm as a starters but suddenly bigger circumference I mean.

[MTWeatherman]

Well, after this is starting to be yesterdays debate, how about the old and reliable one with released boolits... does it reach immediate consensus here, or...? This is an oldie; one 200 grain .30 cal boolit having BC of .400 is dropped from the table at the same time as two other boolits are launched from a rifle. One launched boolit is .30 cal 180 grains having BC of .300, muzzle velocity 2000fps; other launched boolit is similar to the dropped one, .30 cal 200 grain with BC of .400, muzzle velocity 2500fps. All boolits are dropped/launched from the height of 1 yard from the ground level and rifle barrel is aimed exactly parallel to the ground (zero degree, not aimed high or low). Which of the three boolits will hit the ground level first (1 yard drop) and how far from the ground level the other two would be at that exact time? This should be done so, that all boolits will release at the same time; dropping the first one at the same time as other two releases from the muzzle.



If the rifles are parallel to the ground, all would hit at essentially the same time. At least, that would be true in a vacuum. The force of gravity is the same on all the bullets regardless of any forward motion. In the atmosphere, there might be micro, micro, micro second difference in time due to slight variations in wind resistance in falling through that yard of air due to sectional density of the bullets or bullet construction. Thats why a bullet would fall much faster than a feather if dropped through the atmosphere...but...at the same speed in a vacuum. Any difference could be measured by dropping all three bullets from that table to see when they hit....the time it took for each of them to hit when dropped from the table would be equal to the time they hit when fired...assuming they were horizontal when they fell. For our purposes......the bullets all hit at the same time.

[MTWeatherman]

Another fly in the ointment. When a wheel leaves the vehicle, would the diameter not expand, due to centrifugical force on the tire?

If the rotational speed of the tire is the same...the centrifical force will be the same if the tire is on the vechicle or off...no difference. So no change in size as it initially left the vehicle. One might actually argue that since the tire is gradually slowing the minute it leaves the vehicle, the centrifical force is actually decreasing and potentially the size with it but it certainly couldn't amount to much.

Finn...if the tire becomes bigger due to increased circumference it will decrease in rotational velocity because it would require more energy to rotate the larger sized tire...and there is no input of additional energy. The only way rotational velocity will increase is by reducing the circumference of the tire...thereby utilizing the same amount of energy. Bottom line is that once that tire is off the vehicle you can't do anything to accelerate that wheel without applying an outside force.

A flywheel has a large diameter for a reason...its to maximize the amount of energy stored. A 20 lb flywheel stores much more energy than a 20 lb shaft...and the reason is the diameter. It's also why it takes more energy to spin a larger caliber bullet at the same rotational velocity than a smaller one (of equal weight)...and why that larger caliber bullet has more rotational energy when it hits...it gained it on its trip down the barrel. In theory, since slow twists impart less rotational energy to a bullet than a fast one...it should have slightly higher lateral velocity for the same powder charge since more of the energy of the combustion gas is available for lateral acceleration. However, better combustion due to the faster twist may offset this...and since the actual rotational energy is quite low...not much is available to be added to the lateral velocity.

Think I've expounded enough...you're probably tired of listening to this rant by now. I'm gone.

[Finn45]

if the tire becomes bigger due to increased circumference it will decrease in rotational velocity because it would require more energy to rotate the larger sized tire...and there is no input of additional energy. The only way rotational velocity will increase is by reducing the circumference of the tire...thereby utilizing the same amount of energy. Bottom line is that once that tire is off the vehicle you can't do anything to accelerate that wheel without applying an outside force.

I understand that, but still... there's no suddenly bigger circumference actually and there's no bigger rotational mass, but because the load presses wheel against the ground in one spot only, it causes lower circumference speed in that spot? Load is removed and this spot grows up to the lighter load causing some skidding and maybe speeding up that way? Maybe no though... No input of additional energy here that's for sure.

[44man]

I agree that the foam will loosen the points but I shoot into very loose bales and bags. I also shot into water and they still came loose on me when just finger tight.
Some of my tips were unscrewed a full turn or more and I know the arrow did not make a full turn in the bale. I have shot at a bag that the arrow did not penetrate but just bounced off of. There was no change.
Thinking about it seems to indicate that it will happen at the target and at the release and can also be a combination of both actions.
If I use a right hand twist on the fletch, the turn of the arrow should tighten the point at release. When it hits the bale and the point stops before the arrow, it should get even tighter. Why is it that the points get as loose as when I use a left hand twist?
Here is a thought for you! The heavy point with it's inertia does NOT stop turning but the shaft does when it hits the target. This makes the point unscrew in the bale with a right hand fletch.
Now take a left hand fletch where at the release, the point inertia makes the point hold still long enough for the shaft to unscrew, which means that when the arrow stops in the bale and the heavy point is still turning, the point should tighten. BUT IT DOESN'T, WHY?
My points are as loose with either type of fletch and only a washer or pliers to tighten them stops it.
OH SH---T, I have started a real mystery here that can't be explained! Stay away from this one guys, it will turn you all into nut cases!
Maybe this is why boolits are screwy too, the question of the loose points and the loose nuts behind them.

[omgb]

I suspect that the tire passes the truck because of the extra energy it receives as it's slung from the hub. On the axel, its rotation is relative to the center of the axel. As it comes off, its last point of contact will be outside of that center. If it is slung by a lug for example, the lug is located as much as 10 inches off center. That extra leverage pushes the tire ahead faster. Unfettered by the extra mass of the truck and the aditional wind resistance, it moves ahead faster based on that last moment of extra enertia.

OK, thats my theory.

[David R]

I have had a tire come off a trailer twice. It sure passed me because I took my foot off the gas and watched the tire to see what it was going to hit.

One crossed the road with out hitting anything, bounced OVER a wodden fence and got "caught" in a chain link fence like a pitch back. I laughed all afternoon. Then I had to fix the fence.

The other one went off into a field.

David

[Buckshot]

................MTWeatherman , a very fine explaination. Well written and easy to understand. Looks as if you spent some time on that. I can appreciate knowing now why a bullet's energy figures are commonly figured using only it's forward velocity.

I'm reminded of a photo I'd seem any years ago in some shooting magazine or book. They had been shooting into blocks of Dux-seal. That very thick heavy gray clay like stuff. Mt Gianni or any other AC & R tech has probably used the stuff. I don't recall how big the block was, nor do I recall the cartridge. Maybe a 9mm?What I do remember is that the first couple of inches had an interesting circular appearance to it.

I think there were 2 rounded humps right behind the impact face of the block. What I think it represents is the fact that the bullet hit, and it's impact forced the material radially away from it, but at the same time some of this energy was obviously of a twisting nature as that artifact was plainly displayed on the expanded surface of the block.

It was apparent to me that all evidence of rotation finished in the first couple inches, yet the slug continued it's forward motion for some distance . If in fact it had been a 9mm slug with (say) a 16" rotation, it stopped rotating in maybe less then 2" after penetrating the face of the block.

................Buckshot

[MTWeatherman]

Buckshot...thanks appreciate that. It was an attempt to provide “backup” for several posters who were right on with their statements...while trying to refute some incorrect ones. I was prepared for a response back from Starmetal refuting at least parts of what I said.

However, it took over an hour and, while I was at it, the world changed. Starmetal discovered his error and, gentleman that he is, admitted it, apologized, and was on his second plate of crow by the time my post hit. I hadn’t seen those intervening posts when I submitted mine so discovered I was preaching to the choir.

...and Joe, no offense intended so don’t take it as such. We all make mistakes for the same reason, myself included. We figure we know the subject matter and think we’ve proofread our own material...math...word composition...you name it. Problem is we read what we think we said...not what we actually did.

[MTWeatherman]

I understand that, but still... there's no suddenly bigger circumference actually and there's no bigger rotational mass, but because the load presses wheel against the ground in one spot only, it causes lower circumference speed in that spot? Load is removed and this spot grows up to the lighter load causing some skidding and maybe speeding up that way? Maybe no though... No input of additional energy here that's for sure.

Appears the statement was directed at me, so should be polite enough to answer it.

Not totally sure what you’re saying here by lower circumference speed. Just because there is a flat spot on the tire,...it still maintains contact with the ground and would have to be moving at the same speed as the rest of the tire. If that spot were constantly moving slower than the remainder of the tire it wouldn’t take long for that spot to rip the tire apart as it moved around the tire circumference under rotation. When the tire is on the vehicle the flat spot is there...off and its gone...and any change in circumference requires a change in rotational velocity. Seems to me the only possible force that flat spot could exert would occur if there was a slight delay in that flat spot returning to a smooth arc. That would allow it to give a push outward away from the wheels center.. But then any force would be relatively small and either be exerted upward if in contact with the ground...or have no real effect since it would be pushing on air. It would have virtually zero effect on any wheel acceleration.

Keep in mind that wheel can be considered a flywheel. Its got a large amount of energy stored so doesn’t want to slow up or stop easily. It would do a large amount of damage if it hit a car...one off an 18 wheeler could really do damage if not total it. It also takes a good amount of energy to accelerate a rapidly rotating wheel...we’re not talking a tiny push to accomplish it.

With that, I’m done with the wheel issue...promise.

[9.3X62AL]

It's also why it takes more energy to spin a larger caliber bullet at the same rotational velocity than a smaller one (of equal weight)...and why that larger caliber bullet has more rotational energy when it hits...it gained it on its trip down the barrel. In theory, since slow twists impart less rotational energy to a bullet than a fast one...it should have slightly higher lateral velocity for the same powder charge since more of the energy of the combustion gas is available for lateral acceleration. However, better combustion due to the faster twist may offset this...and since the actual rotational energy is quite low...not much is available to be added to the lateral velocity. (End quote)

Fine explanation, MT Weatherman.

AND it prompts a thought or two.......Joe asserts that rotational torquing from bullets fired from his AR-15 with its 1:7" twist adds to its impact energy potential, and Buckshot's observations of the Duxseal impact effects tend to bear this out. Perhaps the combined interests of increasing impact effects AND prompting better combustion explains the ridiculously fast twist rate found in 9mm Para and 40 S&W barrels--1:10" is typical. Such a pitch is at least twice the rate needed for downrange accuracy and stability--a factor favoring INTERNAL and TERMINAL ballistics over external ballistics.

[sundog]

Well, Al, looking at a boolit as a flywheel, that makes sense. A bigger diameter and heavier flywheel takes more energy to get it going, so stopping it would mean more energy expended, because there's more energy stored. sundog

[StarMetal]

Fellows,

Sorry I haven't been around, I'm sick as hell. Got some kind of cold or flu from hell that just won't seem to go away. I was in bed for 14 hrs.

Soon as I'm feeling better and the weather get nice, which this week it suppose to be, I'll going to shoot a milk jug with water, actually two. I'll use those loads I used in my AR, the Hornady 60 gr V-Max. I'll shoot the second jug with my Mod 70 Winnie...we'll see what takes place. Take into concideration the Winnie has a 26 inch barrel and the AR a 20. Will be interesting to say the least.

I think Buckshot is absolutely right about whatever the twist is that's what the bullet turns, but I think this changes when the bullet impacts a bailliistic gelintan or flesh. His 9mm he mentioned bears this out some. I think the main thing with high rotational spin is that in some cases it brings the bullet close to it's structural strength and makes it appear that the addition spin is imparting all this energy when all along the bullet literally explodes with it hits something.

Joe

[Buckshot]

...............Believe it was Rick Jamison who was dinking around one time attempting really high velocity. I did too when my Savage M112 single shot was new to me. I figured with the 26" bull barrel I should be able to get a 4,000 fps velocity average. I did, using some 40 gr PSP Speer's and averaged 4075 fps. Accuracy was surprisingly good up to about 3,800 fps. Groups eventually opened to about 1.5" at 100 yards.

In Jamison's deal he was using a 25-06 and some slugs intended for the 25 ACP. At the later end of his testing, not all the slugs would make it to the target. Many were ending up as gray fog part way there. In other words apparently exploding. His explaination was that the rifling created stress risers in the thin copper jacket. This then caused the jacket to come apart and (he guessed) molten lead core to appear as the gray puff he'd been seeing.

...............Buckshot

[MTWeatherman]

Joe asserts that rotational torquing from bullets fired from his AR-15 with its 1:7" twist adds to its impact energy potential, and Buckshot's observations of the Duxseal impact effects tend to bear this out. .

Looking back at some previous posts...this issue has been batted around for some time now. Let's take a closer look at it.

Yes, a bullet with a 1 in 7 " twist will carry more energy than one fired from a 1 in 10" twist since lateral energy is assumed to be the same but the 1 in 7" has the higher spin energy. The target has to absorb both the linear and spin energy. Joe is correct in saying that his 1 in 7" twist provides more energy. However, I doubt if anything hit by it would notice that difference due to the increased energy alone (keep it mind...its what the bullet does with that spin energy that counts). Lets run the formula from Varmint Al's webpage (actually written by Harral and Bussieres). I don't know how hard Joe pushes that bullet but lets smoke it along...0.224 caliber 60 gr. V-Max bullet driven at 3200 fps.

Here's the data for both bullets:

3200 fps lineal velocity for both...muzzle energy(ME).... 1364.32 fp.
7" twist....329142 RPM...6.89 fp spin energy(SE)
total energy = ME +SE =1371.21 foot pounds
10" twist....230400 RPM...3.37 fp spin energy(SE)
total energy = ME +SE =1367.69 foot pounds

The 1 in 7 inch twist provides 3.52 more foot pounds of energy that the 1 in 10"...a 0.25% gain. If you have a 1 in 10" twist and find that unsettling...bump your velocity up 5fps and you've gained it back...at 3005fps linear ME is 1368.58. Not much gain in spin energy but due to lateral energy, the 10" twist now has about 3/4 fp more striking energy than the 7". Unless your .223 load has a 10fps or less extreme spread, some bullets out of that 10" twist will be carrying equal or greater energy than those from the 7" regardless of any attempt to increase velocity for them.

I will accept that the fact that, depending on the target, the .223 with the 1 in 7" twist may APPEAR to carry more energy than the above numbers would imply. Except for full jacketed bullets designed for target or military purposes, this is a varmint cartridge and bullets are designed to disintegrate as rapidly as possible when striking an object. That is done for both safety reasons (less danger of ricochet) and to maximize the energy dump in varmints(small animals). The bullet is designed with the thinnest jacket possible while still allowing it to remain together at the maximum rotational velocity it is assumed to be used at (push it much beyond this and the bullet will disintegrate in midair). If the bullet is striking near its maximum designed velocity, complete upset will take place when it strikes and it won't need to strike much to accomplish that. At that point, it is the linear velocity that begins the disintegration of the bullet but since the bullet was near the point of disintegrating due to rotational force alone...rotational forces quickly come into play. When the bullet strikes, the nose decelerates but the back wants to still keep moving...this puts outward pressure on the bullet and allows pieces of the disintegrating bullet to break away and fly perpendicular to the bullets path. I agree with Starmetal's recent assessment here. This effect would be there if there were no twist at all. Check it out yourself by throwing a snowball at a flat surface (mudball if snow isn't available) However, the faster the twist the faster the disintegration is likely to occur due to the higher RPM (centrifugal force) initially present. This more "explosive" disintegration is good if an extremely rapid energy dump is desired...OK for ground squirrels or a spectacular splat on a steel plate...not so good if more penetration is needed...like for coyotes where I'd want the slower twist.

It appears that Buckshot did indeed witness that rotation and pretty much what you'd expect...it was there but disappeared significantly before the linear motion ended.

A lot of number transpositions there...check my math before accepting it.

[Pilgrim]

Just for giggles I shot a beer bottle filled with water with my .22-250, 55 gr handload. I was curious as to what might happen. It was a quart bottle, set on top of a fence post, and I was perhaps 30 or so yards away from it when I fired the round. Most educational. I had chunks of glass come back at me 180 degrees from the direction of force and they whizzed when they passed by my head! Remember that water is essentially incompressible and all of the energy that hits that water filled container will be spread out over 360 degrees both vertically and horizontally, except for the area blocked by whatever its sitting on. I knew about the incompressibility stuff even back then, just didn't think that with the speed of that little bullet anything could possibly come back towards me. Wrong. The Lord does protect us fools. To give you some idea of the emotional impact of that little "test", I performed it just short of 40 years ago and can remember where I did it, the weather, etc. etc. I suspect I could even drive up to the spot even though I haven't been back there for nearly 40 years.

Another test we performed with that rifle was on a chunk of plate steel we picked up along the RR tracks we were following one day. The plate was perhaps 1/2 " thick. This time the range was perhaps 100 yards and the same load as mentioned above was used again. I did learn from the first experiment, note the distance away from that plate! :o The .22-250 punched a 3/4" hole entirely through the plate. My .270 (130 gr @ ~ 3000 fps) was also used as a comparison test at the same time. The .270 only dented it. Yes folks, velocity and kinetic energy does account for something. FWIW....Pilgrim

[StarMetal]

Pilgrim

I too performed those railplate experiment. The are the plate under the rail that the spikes go through and in my area they were called fish plates, but they are iron I believe, not steel. We shot at one with a 222, a 30-30, 7x57 Mauser, and a 30-06. The 222 with it little 50 gr bullet put the largest hole in it. The 30-30 didn't go through it, the rest did.

When I get to feeling better I'll shoot those milkjugs with both the AR and Winnie with the same load. I'll put a carboard behind them for Scrounger as he wanted to know what's left of that V-Max after going through the jug with water in it.

Joe

[StarMetal]

MtWeatherman,

One of the gunrag writer, Rick Jamison said he'd never hunt deer with a 22 caliber. Well, he's changed his mind now as there are some new heavyly contructied 22 calibers bullet out for deer hunting. He had a 22-250 built with a faster twist to test them as they were in the 70 and 80 and up bracket.

My best friend was a Marine, he loved the M14, he run down the M16 for over 20 years, but as of not to long ago changed his opinion. He made a statement to me that if he got in his Dodge stepside pickup, that I couldn't kill him driving slowly away from me using my AR15 , but I had to shoot through the tailgate and the bullet had through the front of the bed, the back of the cab, the seat, then him. F.J. Volkner said get your local police dept and FBI and we'll be down to kill him with an AR15. Well we didn't have to do that thank God. I had an old 72 Chrysler truck lid at my place when I lived in Ohio. Well I cut it into four pieces. You know they are double stamped steel, not just a single sheet. I put those four sheets one behind the other for a total of 8 layers. I shot at them with my AR with 55 gr FMJ Nam issue, 55 softnose, 69 gr hollow points, and 62 gr current penetrator. They all blasted right through it , again the more explosive rounds making the bigger holes, that is softpoints and hollowpoints. As an extra one piece had the lock on it and I shot through that and all 8 layers also. I think this would have been representive of shooting at his truck. He agreed and shut up after that test.

Joe

[MTWeatherman]

Perhaps the combined interests of increasing impact effects AND prompting better combustion explains the ridiculously fast twist rate found in 9mm Para and 40 S&W barrels--1:10" is typical. Such a pitch is at least twice the rate needed for downrange accuracy and stability--a factor favoring INTERNAL and TERMINAL ballistics over external ballistics.

I've never been able to figure out the reason for the twist rate either...but the 9mm was developed in conjunction with the Luger. Luger obviously had access to the Greenhill twist formula and knew he could get by with much less twist. He had to have a reason for chosing that 1 in 10 but damn I can't find out what it was. I would guess a book on the history of Luger himself...or military firearms...or something would have the answer.

It doesn't seem likely that old George Luger really thought that adding that tiny fraction of spin energy would make any difference in the utility of his pistol or cartridge. A .356 bullet of 115gr moving 1200 fps gives a spin energy of 2.29...use a 1 in 20" twist and it amounts to 0.57. Linear muzzle energy is 368. Add a military full jacket to the picture and there's little deformation so not much of a "buzz saw" effect.

It would seem to me to be more likely that it could have been economy of production...essentially utilizing the same twist rate the 8mm had and perhaps requiring less investment in equipment. Or perhaps the answer lies in the gun itself. The Luger toggle pistol was very sensitive to operational pressures and they had to be high or they jammed...essentially in the +P class. Perhaps the faster twist was designed so as to help increase pressure enough to reduce any jamming and any boost in energy would have been a side effect.

I'd say that the only reason for the 1 in 10" twist today in the 9mm is its because that's what old George had in the Luger and most manufactures don't see the need to change it. But why that twist in the .40? I guess it works fine with jacketed and they see no need to cater to the cast bullet crowd. Most inexperienced cast shooters quickly give up on cast in the 9 saying you can't use them. We know that's not true...but they are indeed likely to have problems with commercial cast due to bullet size and hardness.

[MTWeatherman]

[QUOTE=BuckshotIn Jamison's deal he was using a 25-06 and some slugs intended for the 25 ACP. At the later end of his testing, not all the slugs would make it to the target. Many were ending up as gray fog part way there. In other words apparently exploding. His explaination was that the rifling created stress risers in the thin copper jacket. This then caused the jacket to come apart and (he guessed) molten lead core to appear as the gray puff he'd been seeing.

...............Buckshot[/QUOTE]


As you already noted...exceed the rotational velocity that the bullet was designed for and it comes apart. The whole issue is related to twist, caliber, jacket thickness and alloy, etc. Formula's have been developed to help determine that speed...however, because a lot of assumptions were made, I'd certainly do my own testing before accepting them.

Varmint Al has done quite a bit of work on this issue...as well as a lot of research on many others which may be of interest to many of you. Granted, it's with condoms... not cast, but the same physics apply. Looks like a pretty weakly constructed .22 bullet he was working with but check out the following link:

http://www.varmintal.com/ashot.htm

There's a pretty good amount of informative reading on that entire page. However, if you want to "cut to the chase", click on "bullet spin" at the top (bottom line in the blue text block) and you'll be there.

[MTWeatherman]

MtWeatherman,

One of the gunrag writer, Rick Jamison said he'd never hunt deer with a 22 caliber. Well, he's changed his mind now as there are some new heavyly contructied 22 calibers bullet out for deer hunting. He had a 22-250 built with a faster twist to test them as they were in the 70 and 80 and up bracket.

I had an old 72 Chrysler truck lid at my place when I lived in Ohio. Well I cut it into four pieces. You know they are double stamped steel, not just a single sheet. I put those four sheets one behind the other for a total of 8 layers. I shot at them with my AR with 55 gr FMJ Nam issue, 55 softnose, 69 gr hollow points, and 62 gr current penetrator. They all blasted right through it , again the more explosive rounds making the bigger holes, that is softpoints and hollowpoints. As an extra one piece had the lock on it and I shot through that and all 8 layers also. I think this would have been representive of shooting at his truck. He agreed and shut up after that test.

Joe

Sorry you've been sick Joe.

I have an ulterior motive here...I'm trying to get my posts up as high as yours before quitting this thread. (joking of course but this has become the "Thread that Won't Die" and I've become a part of it myself)

If you've got a more heavily constructed .22 bullet designed for larger game then it would certainly work for game animals up to the size of deer. Bullet construction has always been the limited factor for use of this caliber on larger animals. The energy of a .223 is beyond the standard 1000 fpe many accept as the minimum standard. That bullet would be designed for some penetration. My previous comments apply only to the much more frequently used varmint bullets such as the V-Max you plan to test.

The results that you and Pilgrim had were no surprise. It's long been established that high velocity is the primary requirement for punching holes in steel. Caliber and bullet construction are secondary. However, this penetration in steel doesn't translate to penetration in flesh (or most other things either). The old 45-70 won't do well on the steel penetration test but don't use a .223 to take it on for penetration in most other material. You might be able to challenge it with a FMJ depending on the .45 bullet used (likely won't have enough velocity with that 70gr to punch the hole in steel)...but I think that would be debatable.

I've been trying to get out to the local range since late last week...first too windy, then it snowed over the weekend. now its melting and turned the range into gumbo. Spending time on this board has been as close as I've been able to get to being able to shoot. Looking at the text I've generated, I've obviously had too much time on my hands. Time to get something constructive done.

[9.3X62AL]

[QUOTE=MTWeatherman] It would seem to me to be more likely that it could have been economy of production...essentially utilizing the same twist rate the 8mm had and perhaps requiring less investment in equipment. Or perhaps the answer lies in the gun itself. The Luger toggle pistol was very sensitive to operational pressures and they had to be high or they jammed...essentially in the +P class. Perhaps the faster twist was designed so as to help increase pressure enough to reduce any jamming and any boost in energy would have been a side effect.

I suspect you are correct on both speculations, sir.

It's pretty clear that A LOT goes on at bullet impact that cannot be objectively explained by ballistic formulae or energy figures. Does anyone know of real-world work done on deer with the Nosler 60 grain Partition in either the 223 or 22-250? Going a little off-topic with this, but the things shoot REAL well in my Mini-14. At their price, THEY BETTER.

[StarMetal]

The Swift 70 Scirocco has a BC of .379 and and if fired at 3075 fps it will retain that noted 1000 foot pounds of energy needed for a good deer kill to near 300 yards. The Nosler Partition, although a good bullet, has a BC of .247 and would run out of steam much closer. Would do ok for close shots though.

Joe

[waksupi]

If velocity is a requisit of punching steel, how come my .358 Win punches through a half inch plate at 200 yards? Starts out at about 2100 fps, so isn't a speed demon. 6.5 does it too at a hundred, and we know they aren't pooping along too fast..

[44man]

I shot a 30-06 tracer at a 2 foot diameter Oak tree. The bullet was sticking half out the other side and the smoke from the tracer was pouring out the near side. So if the enemy was hiding behind a tree of say 12 to 18", he would be hit. What would an armor piercing bullet do? Now show me a .223 round that will go through that much wood! I would rather have an M1 in battle instead of the pipsqueek toy being used now where someone can hide behind trees and block walls while you pour clips full at him with no effect. One good round from the M1 is better then a belt load of clips.
Yes, I too burned holes through steel plates with the .222 and .220 Swift but the same bullet only went inches in wood. The .223 is good if it hits flesh, but most people getting shot at are not standing out in the open.
How many billions of rounds were expended in Nam trying to shoot through a jungle? I would rather take out the jungle and all behind it.
You just can not compare the effects on steel from different calibers and relate it to anything. Most of the larger calibers that do not penetrate steel hit with much more energy over a wider area and explodes the bullet before it can go through. Change the bullet construction of the larger bores and that puny 1/2" or 3/4" plate poses no restriction to penetration. Let's not start comparing apples to oranges. (Reminds me of the straw that went through a telephone pole in a tornado, I never heard of a baseball bat doing that.)
I shot my .475 revolver with a cast WFN boolit at a tree 1 foot in diameter, it went through that one and the small tree behind it. ( The WLN does better and a pointy boolit would do better yet.) It only puts a small dent in steel but makes a huge smoke cloud and a large ring. The .223 will not go through that tree! Which is more effective? which would you rather face in battle? Unless you walk around with a 1/2" mild steel plate in front of you, of course.

[The Nyack Kid]

boy has this tread wandered
FWIW my 300 H&H makes a deeper hole in 1/2 steel plate at 200 yards than my 45-70 does at 100 course to steel plate is T-1 steel .
for a boolit to penitrate steel ,volocity is what is needed the most . a small bullet with a small surface area going 3500 fps has a tremendous amount of energry on the point of impact the bullet with the wider area is going to have its energry spead out over a wider area . the military is using thin hard steel sabots now , for their armor piercing needs .
i better go do something dumb now cause im feeling smart.

[9.3X62AL]

Joe--

Your thoughts parallel mine on the NosPart 22 x 60. Nothing over 100 yards, which takes in all but one deer I've shot locally. This last Alberta trip was the first real long range deer shooting I've been a part of. Those critters are BIG--unlike the blacktails and muleys around here, where there can be a sizing crossover between large jackrabbit and small deer. Those 22 Partitions are one very expensive VARMINT bullet, otherwise.

[The Nyack Kid]

mmmm high speed penitrates steel better than low speed does ....
Eureka ! i have it ( uhh maybe not .Eureka is a 90 mile drive from me) i now starting to under stand the popularity of the RUM WSM magnum super high volocity condo meat mangling wonder blasters.
Animals have been reading gun mags and desided to steel plate themselves the only way to defeat this armor is with a super-duper $5.00 a shot fancy condom bullet @ no less than 3500 fps ....... that deer i got last year with my 45-70 Must have been an illiterate mule deer else it never would have worked.
INC

[44man]

Come on guys, you all know the deer are steel plated and need high speed, tiny bullets to kill them!
Yes this thread has wandered, but has been a lot of fun and we all have learned a lot. We all did some thinking too and at my age it might help. I don't think it is bad to go off course a little. Seems as if there were more posts for the starting question and all the side trips we took then almost any other issue posted in a long time. I enjoyed it so far.

[The Nyack Kid]

Ive done some thinking and despite all the smoke and the burnt hair scent that iniecksplicably ...... unexpaneable ........ ?!? ..... follows me around . the above is the best i can come up with .

[9.3X62AL]

FWIW, the Nosler Partition in 22 caliber might be just what the doctor ordered for our tiny little critters in my area--assuming they work like Partitions are supposed to. Set out from a 223 bolter at 2700-2800, they sound all right on paper, anyway.

The 243 is almost too much for these animals, it seems. The 30-30 just flattened two of them for me, like small plains game with a 375 H&H. Goodness knows my great-grandfather and grandfather shot dozens of these deer with the BP-intensity 44-40 WCF.

[StarMetal]

Al,

Maybe this will help. Like I said Jamison tested all these out of a 1 in 8 barrel in his Savage 22-250 shot into wet newsprint. Here's what the Nosler 60 gr did:

3446 fps velocity....recovered bullet weight of 44.7 grs.....retained weight of 75 %.......penetration 14 inches......expanded bullet diameter of .39 inchs. To give you an idea the Scirocco of 70 grs retained 70 % of it's weight, penetrated 15 inches and expanded to .48....that expansion I think is the big important difference. That's over 45 caliber for the Scirocco, but about 40 for the Nosler.

Joe

[scrapcan]

Hi all,

not hijacking (just helping to keep it hijacked) or making statements, just passing on an interesting article.

There is an article in January-February 2006 issue of American Scientist that may interest some of us.

here is a link

http://www.americanscientist.org/template/AssetDetail/assetid/48547?fulltext=true

if that doesn't work go to home page and it is the cover story. Interesting new technique for recording what is going on.

enjoy.

[StarMetal]

Okay fellows, I said when I was feeling better I'd shoot that milk jug with the Winnie Model 70 Varminter with 1 in 12 twist with the 60 gr Hornady V-Max. The test was just a tad unfair that the Winnie has a 26 inch barrel resulting in more velocity then the 20 in barrel on my AR15, but anyways shot at 100 yards. Big difference. The jug did explode pretty good and the bullet , the whole bullet not fragments like from the AR15, made it through to just stick in the backstop. I have pics of all. First jug is shot with AR15. Second jup is shot with Model 70 Winnie. Third pic is the bullet from the Model 70 shot. In my opinion the fast 1 in 7 twist in the AR15 made quite a difference. Remember the bullet didn't make it through the jug from the AR15. There were fragments of lead and jacket where the jug set. So whatya think?

Joe

http://www.hunt101.com/watermark.php?file=500/7385milkjug.JPG

http://www.hunt101.com/watermark.php?file=500/7385JUG.JPG

http://www.hunt101.com/watermark.php?file=500/7385BULLET.JPG