Do Cast Bullets Blow Up?

[joeb33050]

I'm putting this up in hopes that somebody will check the arithmetic, that somebody will critique the model, and that somebody will do a drawing of the bullet/tube. Maybe 45 2.1 and I are speaking again.

I've seen "vapor trails" from bullets, but can't recall ever seeing a bullet "blow up"; others have seen blow ups.
Will a spinning bullet blow up?
The Centripetal Force (CF) acting on a rotating item = mv^2/r, where CF is in pounds, m = mass in slugs where a slug = weight/g and g = 32.15 and v = feet per second that the item is rotating at.
When CF > tensile strength, the bullet blows up.
The model I use is a spinning bullet and an imaginary tube on the outside of the bullet, with velocity, twist and caliber = diameter.
For a given caliber and twist, I calculated the bullet velocity required to make the bullet blow up.
Here are the results: (A .224 bullet in a 7" twist gun must go 2172 fps to blow up.)

Twist/velocity
.224"
7/2172
8/2484
9/2792
10/3105
11/3416
12/3725
13/4035
14/4345

.308"
9/2528
10/2809
11/3089
12/3370
13/3651
14/3932

.375"
12/3135
14/3657

.457
14/3383
16/3867
18/4350
20/4833

Harder alloys have higher tensile strengths.
It appears to me that if this analysis is correct, lead bullets don't blow up from the spin, because the required velocities are just too high.

There's an internet calculator at
http://hyperphysics.phy-astr.gsu.edu/HBASE/cf.html#cfc.

Thanks;
Joe b.

[jonk]

If that is assuming pure lead AND is accurate, I would think it entirely possible to blow a bullet up- or rather have it fly apart. However, a lot of other factors would come into play- outside temperature, friction and temperature of the projectile from that (and powder burning), bullet shape (the more grooves, the more strength I'd think the bullet would have) etc.

I've not seen it but then I've never pushed a cast bullet of ANY kind much over 1900 fps.

[Larry Gibson]

Joe

I have pushed cast bullets to over 3000 fps but have not had one "blow up". However they were shot in slower 10"+ twist barrels and the required centrifugal force would not have been there. Also I was using harder alloys with higher tensile strength.

On the other hand I have had numerous SX and Blitz jacketed .224 bullets blow up. These were fired out of 7-10" twists at velocities over 3000 fps. In 12" twists I've not had any blowups up through 3250 fps. These bullets will also blow up above 3500 fps in a 22-250 or .220 Swift with 14" twist. I've had one Hornady 6.5 100 gr bullet blow up when shot at 3250 fps out of a M96. Mostly accuracy goes south with them between 2900 and 3000 fps indicating something is happening to the bullet. The Sierra 100 gr HPs on the other hand shoot moa up through 3250 fps.

One of these days I might get around to pushing cast bullets in the sweded above 3000 fps to see if I can get one to blow up. As the acuracy gets gawd awful with bullets not holding paper it would take a large dirt berm at 100 yards and a spotter to see if the bullet impacted and another watching for the tell tale puff of gray smoke when a bullet blows up. Someone else could try this experiment though as there are lots of 6.5 Swede shooters out there. Might try the same with a 7-8" twist .223.

Larry Gibson

[mooman76]

Lee did some experamenting there and when he was approching 4000 fps tey started blowing up!

[HORNET]

I've seen Hornady SX's and Sierra's equivalent blow up out of the .22-250 (small blue-grey cloud and a small "shot" pattern at 50 yd.). I've never seem a cast boolit blow up. Despite the claims of the 9-jillion rpm group, I've usually seen accuracy go beyond useability and stopped increasing the powder charge well below the velocities of the fragmenting J-bullets.
BTW, I've read that Charles Newton had problems with the thin jacketed bullets available at the time blowing up out of his .30 and ended up putting a paper tube inside the jacket to insulate the core from the frictional heat. Don't know how the thermodynamics works out but he said it fixed the problem..

[leftiye]

Hornet - WOW! Thanks for that vignette on Newton. That jacket over paper patch confirms (not proves, but definitely helps) something I've wondered about. I.E. does the better accuracy of paper patched boolits come from the paper protecting the boolit from the barrel only, or does it insulate the boolit too? The reason that is important is that if soft(er) lead can shoot more accurately when insulated from the heat of passage through the bore, it is because it is harder due to not being as (semi melted) hot.

This should directly shed light on the issue of naked cast boolit deformation in the bore (maybe in the air after leaving the bore?). If Newton's bullets blew up before he added the insulation, then the bullet DID obviously get quite hot in the bore, or else in the air, another thing that a lot of folks say doesn't happen. If it were just poor boolit construction causing the bullet blow up, the paper layer would have made it worse (ya think?).

[runfiverun]

leftiye
hope larry doesn't read that last sentence of yours or this thread will be 18 pages long.....................lol...

[Larry Gibson]

Some thought "frictional heat" was not the problem. They suggested that the layer of paper provided a cushining area where the bullet jacket expanded into istead of being cut or sheared by the rifling edges. The jacket material then had almost full strength to withstand the velocity of the 30 Newton.

Larry Gibson.

[MtGun44]

Aerodynamic heating is a significant issue at very high velocities.

Bill

[Larry Gibson]

Aerodynamic heating is a significant issue at very high velocities.

Bill

Yes but are we shooting cast bullets at those speeds for a significant amount of time for it to have an effect?

Larry Gibson

[Larry Gibson]

leftiye
hope larry doesn't read that last sentence of yours or this thread will be 18 pages long.....................lol...

18 pages....surely you jest. Actually I believe leftiye to be correct; were it poor bullet construction the paper would have made it worse.

Larry Gibson

[andrew375]

The vapour trail is just bullet lube, burning or vaporising. You can see this quite often when shooting Minie bullets when there is lube in the base cavity.

[warf73]

I've seen it shooting condom bullets a few times, there are a few videos out there with good footage of vapor trails.

[joeb33050]

Still looking for arithmetic checkers, model critiquers and somebody to draw the model.
The EXCEL workbook is on the book site, at
http://sports.groups.yahoo.com/group/CB-BOOK/ , in FILES, in ERRATA.
Here's another try at the model description.
Thanks;
joe b.


CAST BULLET BLOW UP
Do cast bullets "blow up" because they are spinning? Here's my model:
We start with a cylinder of a certain alloy, diameter = caliber and length also = 1 caliber.
(For example, for a .308" caliber the cylinder diameter would be .308" and cylinder length would also be .308".)
This cylinder may be considered to consist of a tube with .025" wall, diameter = caliber, length = 1 caliber, and a small cylinder with diameter of caliber-.050" and length of 1 caliber.
(For the .308" example, the tube O.D. = .308", I.D. = .258", length = .308"; the small cylinder O.D. of .258", length 308".)
We're interested in figuring out when the tube would "blow up" and leave the small cylinder.
Centripetal force = CF = mv^2/r where CF is in pounds, m = mass in slugs = pounds weight/g with g = 32.15, v = fps, and r = the radius of the small cylinder.
(In the .308" example, r = .258"/2 = .129".)
CF is easily calculated for any caliber/cylinder diameter, tube dimensions, tube length velocity and twist.
Lead has a tensile strength of ~ 2400 pounds per square inch.
I think that when the CF = the tensile strength of the inside area of the tube, that the bullet will blow up. So the question becomes, for a given caliber and twist, at what velocity does CF = tensile strength?
For a .308 cylinder and 9" twist, the velocity must be 2528 fps for CF to = tensile strength. Following are some other twists and required velocities for .308" caliber.
Twist Velocity
10 2809
11 3089
12 3370
13 3651
14 3932

[leftiye]

Larry, Are you feeling okay? Me correct? There has to be something wrong! Don't get mad, I'm just joking with ya.

[Tiger]

If I am correct Larry is thinking frictional heat. If that is correct then I fully agree with him. Look how few rounds of jacketed it takes to heat barrel up. Even with top end cast loads it takes more shot to equal the few jacketed rounds. Some say the burning of the powder creates all the heat. Here is what I think. The burning of the powder is for such short time in the barrel I do not think that it has time to heat it up that fast. Like the finger and candle flame thing. On other hand the friction isn't affected as much with time. Make the time longer yes heat gets worse. I think this great friction heat with jacketed in addition to air friction at very high velocity is the bad guy here. I too am convinced that frictional heat makes extracted cases very hot from semi automatic firearms.

Larry I have seen friends shoot very light bullets very fast from fast twists and not be able to blow them up. I do not think fast rifling adds that much more frictional heat unless it very deep and rough.

Joeb give up all the mathematics you make this much more complicated then need to be.

Ralf

[Larry Gibson]

Joe

The 10" and 12" twist velocities would not be too hard to achieve with a 311359 or similar cast bullet in a .308 or '06. I'm kind of wrapped up in another experiment now or I'd give it a try. Surely someone else can try it?

Also it appears your model is based on a solid cylinder. I wonder what effect, if any, the size and shape of the lube grooves along with the rifling impressions has on the final velocity required.

Larry Gibson

[Larry Gibson]

Larry, Are you feeling okay? Me correct? There has to be something wrong! Don't get mad, I'm just joking with ya.

I haven't gotten mad with you yet. No sense starting now especially when you make an intelligent and non-arguementative comment that is pertinant to the issue.

Larry Gibson

[Larry Gibson]

Ralf

Construction of the jacketed lead core bullet is the controlling factor in whether or not it will blow up. There are 40 gr bullets that do not blow up at 4000+ fps and there are other 40 gr bullets that will blow up at 3500 fps. All from the same 22-250 or .220 Swift. As I stated before I have blown up numerous 55 gr SX, Blitz and Speer HPs in .223s with 7-9" twists at relatively sedate velocities of 2900 - 3100 fps. A stronger (thicker) jacket solves the problem. I also have done the same with 6.5 Swedes and 100 gr Hornady bullets vs 100 gr Sierra HPs.

I would speculate that the burning powder is the major cause of barrel heat. Take two barrels of equal contour, one in .223 and the other in 22-250 and shoot 10 rounds out of each in say one minute. The 22-250 barrel will be considerably hotter. Friction no doubt does contribute some to the heat. How much I do not know but perhaps someone good at math could really tell us. Perhaps Joe.

Larry Gibson

[runfiverun]

larry
i have been called a jester on more than one occasion.

but the heat thing wouldnot the twist rate act to put a boolit in a bbl just a bit longer
or some how expose it to fricton longer [ iknow not much longer]

and wouldn't a higher muzzle pressure have an bad effect on a boolit exiting the bbl.

[Tiger]

Ralf

Construction of the jacketed lead core bullet is the controlling factor in whether or not it will blow up. There are 40 gr bullets that do not blow up at 4000+ fps and there are other 40 gr bullets that will blow up at 3500 fps. All from the same 22-250 or .220 Swift. As I stated before I have blown up numerous 55 gr SX, Blitz and Speer HPs in .223s with 7-9" twists at relatively sedate velocities of 2900 - 3100 fps. A stronger (thicker) jacket solves the problem. I also have done the same with 6.5 Swedes and 100 gr Hornady bullets vs 100 gr Sierra HPs.

I would speculate that the burning powder is the major cause of barrel heat. Take two barrels of equal contour, one in .223 and the other in 22-250 and shoot 10 rounds out of each in say one minute. The 22-250 barrel will be considerably hotter. Friction no doubt does contribute some to the heat. How much I do not know but perhaps someone good at math could really tell us. Perhaps Joe.

Larry Gibson

Larry

I think the friction pays much higher role then we think. Some interesting expriments, which would be very difficult to do, might prove some insight.
One example would be if you could some how attack a compressed gas to the breech of the barrel with a jacketed bullet it in and try achieve high velocity and see what friction heat we get then. Another would be using a very long barrel and see if the additional bullet time in the barrel make a heat difference.

Runfiverun yes fast twist make more friction but I doubt barrel time changes much. Velocity is velocity no matter what the twist. They have run into some problems with the 6.8 SPC. As it come out they give it 10 twist I think because it is 270 caliber. All but the Weatherby 270 Mag have 10 twist the Weatherby 12. The problem they have with 6.8 with Remington ammunition loaded to close maximum was over pressure. The SAAMI specification chamber some problem too. Now I hear they change to 11 twist and little differenct chamber and pressure problem go away. I hear too that they can even increase velocity. It make sense to me. Remington not involved in this change I hear.

Larry you say thing about Newton paper wrap. I wonder if it is to insulate the lead core?

Ralf

[rockrat]

I have had a cast boolit out of a 50bmg disintigrate at about the 70 yard mark. Just a grayish clould and dirt thrown up as some pieces hit the ground. Gun had a 1-9" twist and I was running linotype alloy, that with the loads I had, should have been near to or above 2500fps. A 1-15" twist gun at 2300fps is no problem so far.

[tommag]

I have never done a controlled experiment, but I had one experience with the same rifle, different bbls, and the same load that leads me to beleive that friction may come into play.

I have a 96 swede that had a rough bore and I couldn't push the sierra 85 gr over 2950 without a blue puff 30 ft infront of the muzzle. The bore was pretty rough.
When I put a new bbl on it, I was able to load the same bullet to about 3400 (Don't have my notes with me) without any blow-ups and fair accuracy. I had attributed this to jacket deformation with the rough bore, but perhaps it was the friction that caused this.

[runfiverun]

i lost part of my last post;
but i am wodering if it is not so much the lead. but the SbSn chain.
i have always thought that a balanced sbsn chain was the best mix, even q 2%to ww's
was a far better mix then a smidge of tin to fill the mold.
that is the major reason for my rifle mix of 4/6 or5/6.
i am able to reach quite high velocities with this mix, and it is always the same hardness
even 2-3 years after being made.

but on impact with a rock or hard dirt berm there is a complete break-up of the boolit.

[Tiger]

I have had a cast boolit out of a 50bmg disintigrate at about the 70 yard mark. Just a grayish clould and dirt thrown up as some pieces hit the ground. Gun had a 1-9" twist and I was running linotype alloy, that with the loads I had, should have been near to or above 2500fps. A 1-15" twist gun at 2300fps is no problem so far.

rockrat

I do not know what velocity you get from 9 twist barrel but I figure just for sake of formula 2400 fps. I was searching for the rotation speed of your bullet in fps too. I make your bullet .508 diameter and I find that the rotational speed is double what it is for smaller bullets. The smaller bullets do 200 to 250 rotations per second and your bullet was reading up in the 400 area. Maybe this area truly spin threshold for lead alloy.

Ralf

[garandsrus]

There is an article in Precision Shooting, April 1998 called "Comet Tails" where the author shows a couple pictures of jacketed bullets with what he describes as lead particles, in the shape of comet tails, on the target.

He states that at high velocities the core melts and is released from the jacket via the hollow point of the bullet. The heat is produced by a combination of friction with the barrel and air. The mathematics to support his position are covered in laymans terms.

John

[carpetman]

runfiverun---You lost part of your last post. Yip it blew up. Too much RPM.

[seabreeze133]

They only "blow up" if u put a small explosive charge in them. Nose is preferable.

:o)

[Larry Gibson]

Whether or not the rifling twist increases barrel time is another good question. If there is an increase in barrel time then how that would correlate to increased barrel heat is perhaps another good question. However since one is stuck with whatever the twist is in the barrel one has the answers may just be moot points.

There are numerous magnum cartridges that have quite a bit higher muzzle pressure than do standard cartriidges. Yet they are capable of the same accuracy. I do not think the amount of muzzle pressure is the determining factor. The determining factor most probably is how evenly that muzzle pressure is released around the base of the bullet. If the base of the bullet or the crown of the barrel is defective the pressure will not be released evenly and inaccuracy will result.

Now if you are attempting to lead me down a path here let me say this; don't bother, the RPM issue is what happens after the bullet is in flight.

Larry Gibson

[leftiye]

Larry,
Arguements are what discussion is about! Argument is GOOD. But only when we don't distort what is being alledged, and address what each other actually said, and don't call each other names, or go off on tangents about how the concept was arrived at, or how you like the way I hold my mouth (attitude) etc. (just address the concept). How can I tell you you're wrong without being argumentative? Is it argumentative by definition then? Are you ever "argumentative"?


It's about presenting concepts that DON'T agree with (DO contradict) the conceptual position presented by the other party. Not agreeing IS allowed! (LOL)

[leftiye]

The part of this I am interested in is exploring the role heat of barrel, and especially frictional heat plays in causing lead boolits to soften and deform more in the barrel, and in flight than might be expected if only a straight BHN X1422 were the estimation of the lead strength of the surfaces, and bases, and noses of boolits. All through Larry's RPM thread I kept seeing instances where it appeared that minor deformations were happening when the expectation was that no deformation should be happening. Sorry to be so vague, I just remember many of those happening, but not the specifics, only that I kept wondering if that was the case. For a couple, look at the possibility of Paper patched boolits performing so well due to the paper insulating the boolit, also ask yourself why Cream of Wheat can take the place of a gas check when used as a filler.

[floodgate]

Tiger:

"Larry you say thing about Newton paper wrap. I wonder if it is to insulate the lead core?"

That's what Newton claimed, anyway - and he was a pretty savvy experimenter and designer/inventor (and - sadly - a lousy businessman).

Floodgate

[Larry Gibson]

Tiger:

"Larry you say thing about Newton paper wrap. I wonder if it is to insulate the lead core?"

That's what Newton claimed, anyway - and he was a pretty savvy experimenter and designer/inventor (and - sadly - a lousy businessman).

Floodgate

Floodgate

Tiger (Ralf) either can't read or doesn't pay attention to what he reads. I stated this in a previous post; "Some thought "frictional heat" was not the problem. They suggested that the layer of paper provided a cushining area where the bullet jacket expanded into istead of being cut or sheared by the rifling edges. The jacket material then had almost full strength to withstand the velocity of the 30 Newton." That obviously says something about Newton's paper wrap. Apparently, from other writings, Newton thought the paper provided insulation leading to his success. Some thought otherwise.

My own thoughts on this are; I have serious doubts about the lead alloy melting from air friction. Some calculations say it is so as in the Comet Tails article. However I would ask; I air friction is enough to melt some bullets lead tips at 2640 - 3000+ (velocity listed in the article) then wouldn't that same air resistance melt all the lead alloy tips of bullets, especially those at higher velocity? Problem is we do not see "comet tails" or have bullet blow ups in most bullets shot up through 4200+ fps. Also Wakupsi and I both have reported similar comet tails with cast bullets in the 6.5 Swede at the sedate velocity of 1600-1900 fps. Certainly that is too low a velocity for air friction to melt the bullet alloy.

At one range I was in the 300 yard pits and occasional a bullet would impact in the berm and come back into the pits. Not hard enogh to hurt you but it got your attention. I picked several of these up and they were very hot. Obvious something heated them up. Perhaps there is more heat caused by friction and the powder burning on the base than we think. I don't have the answer to this but it apperars to me there is more to comet tails and bullets blowing up that just heat from air resistance. My guess is it is a combination of factors of which heat is only one.

Larry Gibson

[Tiger]

Larry

Maybe with Swede you see a smoking lube trail? How about many plastic tips today. You think then melt easier or not compare to lead?

Ralf

[joeb33050]

Bullets are hot right out of the barrel, cases are hot right after they eject. BGullets and cases get hot RIGHT AWAY!! Bullets may get hotter later, ???
joe b.

[leftiye]

"Tiger (Ralf) either can't read or doesn't pay attention to what he reads. " Larry Gibson to Floodgate.

Larry, T'would be appreciated if you'd refrain from yer personal insults. Then maybe some of us wouldn't be set off and be so "Obnoxious". Ya think? Otherwise, your comment was informative, and appreciated.

Joe B., Yep, I think you're right, As I said earlier this is quite exciting to me (the boolit temp. issue, not the insults - well, maybe them too), not from a personal vindication viewpoint, but as it is a source of inaccuracy in addition to what has been viewed to be causal before.

[floodgate]

Larry:

Yeah, there's a LOT going on that we don't understand in the exterior ballistics regime. Keep on with your testing , and we'll get some answers.

When we talk about groups getting smaller at longer distances, I assume (I know! I know!) that we mean in terms of angular size (m.o.a.), not actual group size; i.e., a 1" group at 100 and 1-3/4" at 200, not 1" at 100 and 3/4" at 200.

I DO disagree with you on one small point, though: that the bullet always makes the same number of revolutions between muzzle and target, equal to the rifling pitch divided by the target distance. That doesn't allow for the observed fact (high-angle AA shells landing base-down, still spinning) that forward velocity drops off faster than rotational speed, so there will be few "extra" rotations before it hits the target. But that's a VERY minor point and doesn't affect your results.

I wish everyone would show a tad more courtesy and forbearance on this thread, though.

Keep up the good work!

Floodgate

[Tiger]

Hallo floodgate

On the bullet sleeping I mean actual groups size shrink at farther distance. That be 1.5 inches 100 yards then at 300 yards it shrink to .75 inches.

I like your AA shell twist story. Hey there another one. Wonder if the AA shell enter one of Einsteins worm holes? Who knows where end up and how many turns.

Ralf

[Larry Gibson]

Leftiye

It was not meant as a personal attack. I keep trying to get Ralf to read what has already been said. His redundancy of questions when the answers are already presented is somewhat annoying. I have been very kind in answering his redundant questions numerous times on several threads.

"Larry, T'would be appreciated if you'd refrain from yer personal insults." Is this a classic case of the kettle calling the pot black? At any rate, can we just stick with the subject of this thread? If not I'm not going to hijack Joe's thread with further arguement/discussions with you. I do thank you for your final coments, they are we should be saying (probably myself included). So with that I'll stick to the topic here. Thank you for your input.

Larry Gibson

[leftiye]

Yup, I've also seen .375 H&H groups at 100 yds be 2" and only 1" at 200 yds. Yup, same place, same gun, same day, same load.

Larry, Nope, not the pot calling the kettle black. I haven't called you any names, nor called your comments unintelligent and stupid, nor called you obnoxious over and over. I've only asked you yourself (Ralf?) to read and percieve more correctly, and to answer the issues. I have read your test presentation, I don't need to refer to it for more correct information, especially when I am not referring to it. You quoting it doesn't answer any questions either.

[Larry Gibson]

Floodgate

Not sure we are in disagreement there. I too believe; "that the bullet always makes the same number of revolutions between muzzle and target, equal to the rifling pitch divided by the target distance." It's just that the velocity of the bullet (converted to minutes) is also used to calculate RPM. Where are we in disagreement? Where do the "extra rotations" come from?

I also think Hatcher observed in his experiments shooting the M1903 straight up that some bullets came down base first. This is where the detrimental affect of over stabilization actually comes in many believe. A properly stabilized bullet will nose over as the trajectory curves and continue down it's trajectory point first. An over stabilized bullet will not. The point of the bullet (or the center of spin) will remain the same as the angle of exit from the muzzle. Thus at long range the overstabilized bullet is actually, sort of, "belly flopping" in. This "belly flopping" attitude of the bullet to the angle of incidence is dterimental the the BC which decreases max range and accuracy. Or so many believe.

Some evidence of this was observed back when we used to mex/match M118 with 168 MKs. It was noticed when shooting 1,000 yard matches that M21s with 12" twist barrels the mex/match ammo would just stay sonic the target. Match M14s with 10 or 11" twists would not. Velocities between the barrels were almost the same with some of the faster twists having slightly higher velocity. It was speculated that the bullets from the 12" twists were nosing over, holding their BCs and thus retaining velocity. The bullets from the 10-11" twists were coming down belly first, losing their efficient BC and not retaining velocy and thus were dropping under the speed of sound sooner. Makes a certain amount of sense. The adverse affect (assuming this line of thought to be correct) of over stabilization would thus be greater at farther ranges.

Not sure what this has to do with cast bullets blowing up but is an interesting thought anyway.

Larry Gibson

[Larry Gibson]

....Larry, Nope, not the pot calling the kettle black. I haven't called you any names, nor called your comments unintelligent and stupid, nor called you obnoxious over and over. I've only asked you yourself (Ralf?) to read and percieve more correctly, and to answer the issues. I have read your test presentation, I don't need to refer to it for more correct information, especially when I am not referring to it. You quoting it doesn't answer any questions either.

I wasn't referring to you specifically.

"You quoting it doesn't answer any questions either". I find this obnoxious and just arguementative. Quoting what someone else said is proper. If you are referring to me quoting the results of my own tests and simply agree with you, sorry old boy, ain't gonna happen unless you are correct. Instead of just questioning why don't you proffer up some tests of your own. I'll ask you the same as I've ask Ralf; put up or shut up. I know you won't do it and will just come back with another non answer. At least I've offered you the chance.

BTW; what does my test presentation have to do with cast bullets bloing up? It has nothing to do with it. Kindly stick to Joes thread topic here. If you want to continue this go back over to my thread. That's the proper place to discuss my test.

Larry Gibson

[leftiye]

Well, Maybe you can hit a target, but you missed that totally. It's easier than getting it right, right?

[leftiye]

"Instead of just questioning why don't you proffer up some tests of your own. I'll ask you the same as I've ask Ralf; put up or shut up. I know you won't do it and will just come back with another non answer. At least I've offered you the chance." Larry Gibson

Sounds like a cop out to me. So, Larry, I should not address you until I've conducted an experiment, so I can have test data to show you (like you'd listen to that anyway)? That should make a timely situation , - three months in the furure I'd be done with the paper work. The situation needing a response would be gone and forgotten by then. You'd prefer that I imagine. Sounds to me like it's just a dodge. After all, Ralf does research, and tells you about what he's found, and he gets the same old treatment.

Btw, I wasn't ever discussing your test, I was discussing your illogical argumentation.

[floodgate]

leftiye:

"Yup, I've also seen .375 H&H groups at 100 yds be 2" and only 1" at 200 yds. Yup, same place, same gun, same day, same load."

Hmmm... I'd have to see that myself, to be convinced. I could believe one group fired at 100 yds. going 2"; and a second group - same load, same rifle, same conditions - doing 1" at 200. BUT to sell me on this one, it'd have to be done with ONE group, fired THROUGH a screen at 100 and going 2", and THEN continuing on to the 200-yd. target and scoring 1". Not saying it isn't possible, but I'd have to see it done that way.

floodgate

[floodgate]

Larry:

"Not sure we are in disagreement there. I too believe; "that the bullet always makes the same number of revolutions between muzzle and target, equal to the rifling pitch divided by the target distance." It's just that the velocity of the bullet (converted to minutes) is also used to calculate RPM. Where are we in disagreement? Where do the "extra rotations" come from?"

From the flight time that stretches out as the bullet slows down along its trajectory. The rpms are figured from the velocity at exit from the muzzle, but as the bullet slows in forward motion, each successive rotation takes it a slightly shorter distance, so it takes more turns on the way to the target.

But, as I said, it's a minor point relative to your experiments, and shouldn't affect your conclusions by any significant amount.

On your other point - that a faster spinnng bullet is less likely to "follow the arc of the trajectory" and will end up "seeing" more air resistance (hence a poorer BC) - there's been a LOT of argument among ballisticians about this, and precious few actual observations. The "straight-up, straight-down" AA shell observations are a special case, where the "trajectory" is a straight line up, and then back down, and the shell is never out-of-line with its path and never sees the "extra" drag. You have the BC of its nose shape going up, and the much poorer BC of its butt-end coming back down, but no curve to set the shell "crooked" vs. its path. IIRC, AA fire a couple of degrees off vertical, does NOT have the shells coming down butt-first, but usually tumbling; but I've never seen the experiments myself.

floodgate

[leftiye]

Flood,
My take on this is a badly yawing boolit at 100 yds stabilizes by the time it reaches 200yds. Say it was supposed to make 1/2" groups at 100 yards, but is spiraling around its line of trajectory in a 1" plus wide spiral, and printed on the target at the outside (from the center of the group/target) of its spiral, you'd get a 2" plus group, and at 200 yds, a 1" group.

I haven't performed the coaxial targets test myself, and it was 20 years ago (I think), but I think that maybe someone associated with Wolfe Pub. Co. did in one of their articles. Could be wrong. I have read several articles where they got better groups at 200 than they did at 100.

I can see how you could be skeptical. How about if a whole string of 100 yard groups were bigger than a whole string of 200 yd. groups? Same gun, etc.

[Larry Gibson]

leftiye

That's a "cop out" pure and simple. Everyone knows this series of tests will go on throught the summer. You have plenty of time to conduct your own test. The intelligent thing to do to refute test data is with other test data. Opinions just don't cut it. I've yet to see the results of any test Ralf has conducted. He only quotes others and offers opinions too. Come forth with some test data to back up your opinions. I have, you haven't.

Larry Gibson

[floodgate]

leftiye:

" How about if a whole string of 100 yard groups were smaller than a whole string of 200 yd. groups? Same gun, etc."

Now, THAT might convince me.

Fg

[Larry Gibson]

Floodgate

RPM is not based on the distance traveled. If I read your explanation correctly you are saying the RPM actually is increasing as the bullet slows down? Whether the bullet is going 1000 fps or 3000 fps out of a 10" twist barrel it will still make the same number of revolutions traversing 100 yards. The rotaion of the bullet is still every 10 inches of forward movement even as the velocity slows. "so it takes more turns on the way to the target" if that were the case then the RPM would actual be increasing wouldn't it?

I believe there have been numerous observations and a lot of agreement as to over spun bullets not following the arc of trajectory. For a good explanation of this go to the site Ralf provided; http://www.nennstiel-ruprecht.de/bullfly/index.htm and click on "Over stabilized bullet on a high angle trajectory".

Larry Gibson

[runfiverun]

now i know for a fact that the highpower boys [with jbullets]
use a different 300yd load then they use for 600yds,
if their 300yd load is settled down by then is should be on a frozen rope by 600yds
so why the change in loads? i am pretty it isn't to just put two more grains of powder in the case !!
and iam dmn sure if that was the case they would just shoot the two more grain load!!
at the 100 , 300 , and 600 yd lines.

[Tiger]

Floodgate

RPM is not based on the distance traveled. If I read your explanation correctly you are saying the RPM actually is increasing as the bullet slows down? Whether the bullet is going 1000 fps or 3000 fps out of a 10" twist barrel it will still make the same number of revolutions traversing 100 yards. The rotaion of the bullet is still every 10 inches of forward movement even as the velocity slows. "so it takes more turns on the way to the target" if that were the case then the RPM would actual be increasing wouldn't it?

I believe there have been numerous observations and a lot of agreement as to over spun bullets not following the arc of trajectory. For a good explanation of this go to the site Ralf provided; http://www.nennstiel-ruprecht.de/bullfly/index.htm and click on "Over stabilized bullet on a high angle trajectory".

Larry Gibson

Larry/Floodgate

Let us try this. See if I am on same thought. We like the tire stories. Say you drive your car to store 10 miles away from home. First time you drive 60 mph all way to store. Next time you drive 30 mph all way and final last time you vary your speed much. The odometer in all three cases read same 10 mile distance no matter forward velocity of car change and rpm of tire change. Did I think right? Is that kind what you meant Floodgate? Larry you with me? Sound right?

Ralf

[runfiverun]

that is correct
if you look at a tire chart they will tire x rolls 200 times per mile and tire y rolls 400 timesper mile.
dont matter if it is at 60 or 20 still the same distance around the tire and a mile is still
5280' even in metric.

[leftiye]

"leftiye

That's a "cop out" pure and simple. Everyone knows this series of tests will go on throught the summer. You have plenty of time to conduct your own test. The intelligent thing to do to refute test data is with other test data. Opinions just don't cut it. I've yet to see the results of any test Ralf has conducted. He only quotes others and offers opinions too. Come forth with some test data to back up your opinions. I have, you haven't. "

Larry Gibson

Larry, so what percentage of this (or any other) population has conducted a scientific study? Are we only to listen to and give commonly decent attention to those who have? Are we too superior to give conscientious responses to all comers?

I have no problem with what you are saying now. I agree that I could do some tests, but I object to you using the fact that I haven't yet done so as an excuse to ignore the arguments I present. I agree that facts are preferrable to opinions, but one must travel the trail, not demand the trail to change first. Your own argument would say that you're the one with the theory, and you must defend it, not refuse challengers without considering their arguments at every oportunity. What I object to is hearing it every time (or almost) that I open my mouth (type a post). My point was that throwing the "put up proof or shut up" glove more than once in a great while is just another of your distractions which you prefer to just plain debating the concepts, and theories presented to you (and that you use instead of doing so). Were you a government employee in another life, or are you still one?

[leftiye]

Y'all need to see Tiger's post # 390 on the RPM thread. It should put the "bullets going to sleep" issue to sleep.

[joeb33050]

The vapour trail is just bullet lube, burning or vaporising. You can see this quite often when shooting Minie bullets when there is lube in the base cavity.
"Vapor Trails" were frequently seen on warm humid summer evenings with .222 s and jacketed bullets.
joe b.

[joeb33050]

Joe

The 10" and 12" twist velocities would not be too hard to achieve with a 311359 or similar cast bullet in a .308 or '06. I'm kind of wrapped up in another experiment now or I'd give it a try. Surely someone else can try it?

Also it appears your model is based on a solid cylinder. I wonder what effect, if any, the size and shape of the lube grooves along with the rifling impressions has on the final velocity required.

Larry Gibson

Larry;
We know we can't shoot pure lead bullets at high velocity. As we add tin/antimony, the tensile strength increases and equilibrium velocity increases.
The model says that a WW .308" 10" twist bullet "blows up" above 4350fps, 12" twist = 5220 fps, 14" twist = 6090 fps.

The model, and I'm not defending it, can predict centripetal force for a particle of any size, anywhere on the bullet. I fail to see why lube grooves or rifling marks affect the outcome, as long as there is no "tearing" of any surface.
joe b.

[joeb33050]

Joeb give up all the mathematics you make this much more complicated then need to be.

Ralf

Ralf;
The math makes it EASY for me to see what's going on. Maybe you need some help with the math. Let me know.
joe b.

[joeb33050]

I have had a cast boolit out of a 50bmg disintigrate at about the 70 yard mark. Just a grayish clould and dirt thrown up as some pieces hit the ground. Gun had a 1-9" twist and I was running linotype alloy, that with the loads I had, should have been near to or above 2500fps. A 1-15" twist gun at 2300fps is no problem so far.

A .510" 9" twist barrel will stabilize a bullet 4.350" long according to Greenhill, weighing ~2085 grains according to Brennan. I can't imagine why a 9" twist.
However, in lino the model says the bullet will blow up at 4361 fps.
A .510 15" twist barrwl will stabilize a bullet 2.601" long weighing 1247 grains, same sources.
Model says blow up at 7268 fps, so you're probably safe.
Why the fast twist?
Thanks;
jope b.

[joeb33050]

The part of this I am interested in is exploring the role heat of barrel, and especially frictional heat plays in causing lead boolits to soften and deform more in the barrel, and in flight than might be expected if only a straight BHN X1422 were the estimation of the lead strength of the surfaces, and bases, and noses of boolits. All through Larry's RPM thread I kept seeing instances where it appeared that minor deformations were happening when the expectation was that no deformation should be happening. Sorry to be so vague, I just remember many of those happening, but not the specifics, only that I kept wondering if that was the case. For a couple, look at the possibility of Paper patched boolits performing so well due to the paper insulating the boolit, also ask yourself why Cream of Wheat can take the place of a gas check when used as a filler.

I think tensile strength of lead alloy is ~ 480 X BHN. See "The Fouling Shot", #96, page 6, C.E. Harris.
Cartridge cases are hot when they come out of an autoloader, 22 rf on up. We all know that. I think bullets are hot coming out of the barrel, thought I knew that but don't know the source or experience.
When the bullet slows down in dirt or snow or sawdust or air, it has to give up energy and turns that energy into heat-maybe a little into moving the dirt etc..
Maybe a bullet is hot, heated up in the barrel.
Maybe a bullet heats up from air friction.
As lead alloys heat up, strength goes down.
I'm hard pressed to imagine a way for we laymen and women to measure the heating up if it happens.
This may be of importance, but I'm stuck on how to measure.
joe b.

[Tiger]

A .510" 9" twist barrel will stabilize a bullet 4.350" long according to Greenhill, weighing ~2085 grains according to Brennan. I can't imagine why a 9" twist.
However, in lino the model says the bullet will blow up at 4361 fps.
A .510 15" twist barrwl will stabilize a bullet 2.601" long weighing 1247 grains, same sources.
Model says blow up at 7268 fps, so you're probably safe.
Why the fast twist?
Thanks;
jope b.


Joeb

Thank you for math help but I think I am ok.

Joe do your math to find the rotation speed of bullet rockrat shot in the 50 caliber with 9 twist in feet per second. Remember we talk normal average for smaller caliber around 250. See what you come up with and post.

Ralf

[floodgate]

Larry, Tiger:

"RPM is not based on the distance traveled. If I read your explanation correctly you are saying the RPM actually is increasing as the bullet slows down? Whether the bullet is going 1000 fps or 3000 fps out of a 10" twist barrel it will still make the same number of revolutions traversing 100 yards. The rotaion of the bullet is still every 10 inches of forward movement even as the velocity slows. "so it takes more turns on the way to the target" if that were the case then the RPM would actual be increasing wouldn't it?"

No, the RPM stays constant (pretty much, less a slight slowdown) as established at the muzzle, but the forward speed of the bullet slows due the drag, so the "other" minutes - time of flight - stretch out, hence the number of turns increases at the spin RPM.

Tiger, taking your tire analogy, consider a tire slowly going flat: it gets smaller as the air bleeds out, and makes a few "extra" rotations per mile - before you notice it and stop to change it.

But, as I said, the point is really trivial and I'm not going to push it any further ; let's let Larry get on with it.

Fg

[leftiye]

Joe,
I'm right there with you on all of that. You said it just like I was thinking. Yes we must be careful to separate the heat caused by impact from the other heat. A.223 with an SX bullet will still penetrate a 1/4" steel plate even though it's one of the most frangible bullets going. The bullet melts the steel in front of it. Remember that inside the bore the issue with lead is strength to resist Plastic deformation (plastic limit).

Yup, it's an obscure issue, and hard to detect, because all of it's manifestations either look just ike what the other deformations cause, in fact they are the other deformations, the heat only makes them worse (if such heat actually happens, and I think it's very probable), or at the end of the flight, as you say the deformation from impact makes the deformations we are talking about inintelligible.

[leftiye]

leftiye:

" How about if a whole string of 100 yard groups were smaller than a whole string of 200 yd. groups? Same gun, etc."

Now, THAT might convince me.

Fg

Flood, See Ralf's post # 390 on Larry's RPM thread. 18,000 rounds.

[joeb33050]

Joeb

Thank you for math help but I think I am ok.

Joe do your math to find the rotation speed of bullet rockrat shot in the 50 caliber with 9 twist in feet per second. Remember we talk normal average for smaller caliber around 250. See what you come up with and post.

Ralf

Ralf;
A .51" bullet, 9" twist, 2500 fps is going 200,000 RPM, rotational speed of 445 feet per second.
If I did it right.
joe b.

[RFWobbly]

Cast boolits can indeed "blow up" if the boolit in question is a cast Civil War iron cannonball, still filled with black powder.

See..... http://www.inrich.com/cva/ric/news.apx.-content-articles-RTD-2008-02-21-0099.html

[rockrat]

joeb33050--The 9" twist is what Klaus Horstkamp (sp?) was using at the time I purchased the rifle, back in the late '80's. Most rifles now use the 15" twist.

[Tiger]

Ralf;
A .51" bullet, 9" twist, 2500 fps is going 200,000 RPM, rotational speed of 445 feet per second.
If I did it right.
joe b.


Joeb

I get same thing. What I after here is that the 445 rps is double what it be for 30 caliber bullet almost. That has to have much effect on this big caliber
lead bullet. By way I use .508 for diameter of bullet not knowing what rockrat use but we come close in our figures

Ralf

[joeb33050]

Cast bullet blow up may/does have something to do with the temperature of the bullet. As the temperature increases the tensile strength decreases, and the velocity/rpm at which centripetal force equals tensile strength decreases-making blow up more possible/likely.

A (cast) bullet is heated up by the powder gas and by the friction of the bullet rubbing on the barrel. This until the bullet exits the muzzle.

After leaving the muzzle a bullet temperature may increase from air friction, or may decrease as the air cools the bullet. I don't know the net effect.

I think that I do know that as a bullet loses velocity and energy as it goes through the air; the energy has to go to heating up the bullet and moving (and heating) the air.

We know how much energy the bullet has, and loses. How much energy does it take to heat up a bullet?

The Lyman Cast Bullet Handbook, 3rd edition, tells us that the 311291 at 2500 fps loses 377 foot-pounds of energy in the first 50 yards of travel. The same bullet starting at 1400 fps loses 107 foot-pounds of energy in the first 50 yards.

If the calculations are correct, it takes 12.8 foot-pounds of energy to raise the temperature of a 170 grain lead bullet 500 degrees Fahrenheit.

The bullet loses 377(mv = 2500 fps) or 107(mv = 1400 fps) foot pounds of energy in the first 50 yards of travel, and it would take 12.8 foot pounds of energy to raise the temperature 500 degrees Fahrenheit.

Doesn't mean that the temperture does go up, just that the energy loss is there, sufficient and available.

I found one site talking about measuring the temperature of a bullet as it left the muzzle;
http://www.rangerats.org/bullet.html
where they found the temperature of a 5.56mm NATO bullet leaving the muzzle was 267 degrees C = 513 degrees F.
The author mentions that "The bullets cooled as they traveled away from the gun."

Stay tuned;
joe b.

[leftiye]

Joe B
The first part of that is real close to what I was thinking. Remember (I know you're more interested in boolit blowup) that deformation is happening at a faster pace while in the barrel due to this heating lowering plastic deformation strength too, and that this is affecting accuracy. As for the question of heating in the air it may be easier (for one of our mathematicians) to find some info on heating from friction as per velocity itself, rather than trying to separate energy loss into its various components.

The (IR?) measurement of the temp of the .223 bullet was interesting; very likely hot enough to affect the characteristics of lead. Bad news is that a lead boolit probly wouldn't get that hot (less friction, and less pressure/lower flame heat). So we need to know at what temp lead starts to lose its strength, and how hot lead boolits are likely to get. Great thread!

[joeb33050]

Joe B
The first part of that is real close to what I was thinking. Remember (I know you're more interested in boolit blowup) that deformation is happening at a faster pace while in the barrel due to this heating lowering plastic deformation strength too, and that this is affecting accuracy. As for the question of heating in the air it may be easier (for one of our mathematicians) to find some info on heating from friction as per velocity itself, rather than trying to separate energy loss into its various components.

The (IR?) measurement of the temp of the .223 bullet was interesting; very likely hot enough to affect the characteristics of lead. Bad news is that a lead boolit probly wouldn't get that hot (less friction, and less pressure/lower flame heat). So we need to know at what temp lead starts to lose its strength, and how hot lead boolits are likely to get. Great thread!

I know that cast bullets can/do "deform" in the barrel; the pressure of sizing bullets in my 450 increases nose diameter .001" at least. How much bullets "deform" has to do with the size and shape of the bullet. A Pope style tapered breech-seated bullet probably doesn't deform much. A 311291 with undersize nose may have the nose deform a lot. As long as deformation is symmetrical, I don't think accuracy suffers.

The bullet gets hot from the gas and from the friction. I suspect the friction causes little heat, I'm going to try pushing bullets through the bore after they get in the barrel and after stiction.

I'm interested in both the blow up and deformation.
joe b.

[HORNET]

This thread got much better than I'd expected. A couple more tidbits to stir things up again. That 513 degrees for the 5.56 bullet is above the melting points of linotype and wheelweights according to the LASC data. I really doubt that the entire mass of the bullet reached this temperature due to the thermal barrier caused by the jacket/core interface as well as the time factor (heat transfer DOES take time) but I expect that at least the outer surface of the jacket got that hot from friction and then cooled as the heat transferred to the core (and some loss to the air). I would expect to see the same type of heat transfer on a cast boolit with the outer few thousandths reaching a much higher temperature than the main mass and then cooling off as the heat conducts inward.
FWIW, I did a websearch for the coefficients of friction and found that the kinetic coefficient of friction for unlubed materials is rated at 0.43 for copper-on-steel and 0.95 for steel-on-lead. Assuming equal bearing surface areas and pressure curves, the unlubed lead boolit should generate even more frictional heating. Of course, somebody with much more range time available than I have (working long hours bites), could load up some samples of cast (lubed and unlubed- might want to use COW with all loads to control leading on the unlubed but maintain the same load characteristics) and jacketed of similar weight and engraved length and run them across the chronograph. The velocity differences should correspond to the differences in energy lost due to friction.

[Tiger]

The heat that is transferred from the ignited powder to the barrel and action is not used for propelling the projectile and is lost and wasted. Only about 30 percent of the heat created is gainfully used to expand the gas and push the bullet. Another 30 percent is wasted on heating the barrel and the 40 percent balance goes to recoil, noise, and escaping at the muzzle. With only about 30 percent being useful in creating kinetic energy, a firearm is not an efficient machine.

The heat produced can exceed the melting point of the steel in the barrel. The short time the heat is influencing the metal is the only thing saving it from greater damage. The temperature might reach about 5,550 degrees Fahrenheit and most barrel steel will melt at about 2,500 degrees Fahrenheit. The heat is dispersed by radiation into the air and by conduction into the stock and anything else touching it.

This from internet not from me. The next too from internet: From: ahahma@utu.fi (Arno Hahma)
Subject: Re: Barrels and rapid fire
Organization: University of Turku, Finland

In article <1993Jun19.234436.25614@btree.uucp> btree!hale@UCSD.EDU (Bob
Hale) writes:

#Ok, then I have to ask: why does a barrel get red-hot just short of
#the muzzle when it is rapid fired? Obviously the muzzle end gets

For at least two reasons. The barrel is usually thinnest close to the
muzzle - less material to heat up. The bullet is moving at its fastest
near the muzzle. A portion of the heat comes from friction, but the
gases also do heat the barrel a lot.

#is higher when the pressure is that much lower. It is also hard for me
#to believe that the specific heat of the gas is high enough to cause
#much heating of the barrel.

You forget the gas is under a very high pressure. It has quite a high
density and it is flowing fast with a turbulent flow. All that makes
the heat transfer efficient, although the gas has a low heat capacity
per unit volume. However, per unit _mass_ it certainly has a higher
heat capacity than metals do. When you fire the gun, all of the gas is
inside the barrel, i.e. as many grams as there was powder in the
chamber.

Consider also the energies stored in the moving bullet and the powder.
A typical .30 cal rifle will fire its bullet at a muzzle energy of
about 3 kJ. For that purpose, you burn up about 3 grams of powder,
which contains about 12 kJ of thermal energy. Where does the rest go?
Answer: to heating the barrel and to residual heat of the muzzle gases.
There is much more thermal energy available from the gases than from
the bullet.

#On the other hand, the velocity of the bullet is greatest at the
#muzzle. It looks like the heating at the muzzle is due mostly
#to the friction between bullet and barrel.

You are correct, the bullet friction also heats the barrel and its
effect is largest at the muzzle. At the same time, the heating effect
of the gas gets lower, as the gas cools down due to expansion and the
pressure drops making the heat transfer less efficient. The heating due
to the gases is largest near the chamber, where you get the peak
pressure. This is also the location, where the barrel heats a lot, a
few centimeters from the chamber you will find a hot place. However,
that is also where you have the thickest steel to absorbe the heat.

If you doubt a hot gas flow can heat metals inefficiently, then how
about trying to heat a piece of steel with an oxyacetylene flame? When
powder burns under pressure, it generates 2300..2800 K and the gases
are under pressure of a few thousand bar. In an acetylene flame you
have 3400 K at 1 bar pressure only and you can weld with that...


Okay I like know how they got the temperature of 5.56 bullet near muzzle when hot gases escaping too. Hot gases go far from muzzle also.

Ralf

[leftiye]

It may not melt, maybe it just heats up enough that the metal gets soft? Yes lead doesn't conduct heat very well. So when the interior may not be so hot because of this, the surface is much (emphasis) hotter instead. Maybe molten, maybe just soft. Saying that these gasses that are so many times hotter than the melting point of lead erode boolits during blowby but don't melt the lead is like saying that a plasma torch cuts steel without melting it. Have you read the posts here describing "feathering" of the edges of the driving bands during blowby with the feathering pointing forward?

[joeb33050]

The heat that is transferred from the ignited powder to the barrel and action is not used for propelling the projectile and is lost and wasted. Only about 30 percent of the heat created is gainfully used to expand the gas and push the bullet. Another 30 percent is wasted on heating the barrel and the 40 percent balance goes to recoil, noise, and escaping at the muzzle. With only about 30 percent being useful in creating kinetic energy, a firearm is not an efficient machine.

The heat produced can exceed the melting point of the steel in the barrel. The short time the heat is influencing the metal is the only thing saving it from greater damage. The temperature might reach about 5,550 degrees Fahrenheit and most barrel steel will melt at about 2,500 degrees Fahrenheit. The heat is dispersed by radiation into the air and by conduction into the stock and anything else touching it.

This from internet not from me. The next too from internet: From: ahahma@utu.fi (Arno Hahma)
Subject: Re: Barrels and rapid fire
Organization: University of Turku, Finland

In article <1993Jun19.234436.25614@btree.uucp> btree!hale@UCSD.EDU (Bob
Hale) writes:

#Ok, then I have to ask: why does a barrel get red-hot just short of
#the muzzle when it is rapid fired? Obviously the muzzle end gets

For at least two reasons. The barrel is usually thinnest close to the
muzzle - less material to heat up. The bullet is moving at its fastest
near the muzzle. A portion of the heat comes from friction, but the
gases also do heat the barrel a lot.

#is higher when the pressure is that much lower. It is also hard for me
#to believe that the specific heat of the gas is high enough to cause
#much heating of the barrel.

You forget the gas is under a very high pressure. It has quite a high
density and it is flowing fast with a turbulent flow. All that makes
the heat transfer efficient, although the gas has a low heat capacity
per unit volume. However, per unit _mass_ it certainly has a higher
heat capacity than metals do. When you fire the gun, all of the gas is
inside the barrel, i.e. as many grams as there was powder in the
chamber.

Consider also the energies stored in the moving bullet and the powder.
A typical .30 cal rifle will fire its bullet at a muzzle energy of
about 3 kJ. For that purpose, you burn up about 3 grams of powder,
which contains about 12 kJ of thermal energy. Where does the rest go?
Answer: to heating the barrel and to residual heat of the muzzle gases.
There is much more thermal energy available from the gases than from
the bullet.

#On the other hand, the velocity of the bullet is greatest at the
#muzzle. It looks like the heating at the muzzle is due mostly
#to the friction between bullet and barrel.

You are correct, the bullet friction also heats the barrel and its
effect is largest at the muzzle. At the same time, the heating effect
of the gas gets lower, as the gas cools down due to expansion and the
pressure drops making the heat transfer less efficient. The heating due
to the gases is largest near the chamber, where you get the peak
pressure. This is also the location, where the barrel heats a lot, a
few centimeters from the chamber you will find a hot place. However,
that is also where you have the thickest steel to absorbe the heat.

If you doubt a hot gas flow can heat metals inefficiently, then how
about trying to heat a piece of steel with an oxyacetylene flame? When
powder burns under pressure, it generates 2300..2800 K and the gases
are under pressure of a few thousand bar. In an acetylene flame you
have 3400 K at 1 bar pressure only and you can weld with that...


Okay I like know how they got the temperature of 5.56 bullet near muzzle when hot gases escaping too. Hot gases go far from muzzle also.

Ralf
Ralf;
First you and your sources should differentiate between HEAT and TEMPERATURE. Heat is a quantity, like a pound or a kilogram. A certain amount of heat will raise the temperature of a mass of EX water by a numkber of degrees. A calorie raises a gram of water a degree C. A calorie is a quantity of heat.
Temperature is a measure of ~ intensity~, like speed. Something at 5000 degrees C,hot, but depending on the mass may not contain much heat. A lit match may hhave a high temperature, be hot, but doesn't contain much heat.
So the HEAT doesn't exceed the melting point of the barrel, the TEMPERATURE does. Since the HEAT isn't sufficient to raise the temperature of the barrel to the melting point, no melting.

Second; everything I know tells me that my gun barrels heat up at te chamber end first. My guns, over many years. Not at the muzzle.

Third, I suspect that friction makes little of the heat in the bullet. Yesterday the idiot next to me shot his M1 and the brass landed on my bench. That brass is HOT!!! I made him go away. From an autoloader, brass is HOT, the temperature is high. From a bolt gun, the brass is NOT HOT, unless the operator is very fast. The brass gets hot from the burning gas. If it comes out of the gun quick, it stays hot. If it stays in the chamber of a bolt rifle, it cools down quick. I take each case out of the rifle and wipe it off, bolt gun. I don't ever remember a hot case. But I shoot lead, slow, and take my time. Maybe a fast jacketed fast operator will experience hot brass
Anyhow, if the brass gets hot, the bullet gets hot. The AREA of the bullet base is much smaller than the area of the case inside, but I'm suspecting that the bullet gets hot from the gas mostly, friction less. I'm not having much luck figuring the heat gained from friction of the bullet.

Fourth, if you want to understand the bullet tempperature measurement, go the the site. It's there, and their experiment.

Summore: The velocity is NOT always greatest at the muzzle. (22 RF, 48" barrel; some of my loads, see the whole plinker/subsonic business) Friction bore/bullet is NOT greatest at the muzzle. Bullet is completely sized to the barrel.

Please be careful, apply your critical faculty before posting.

Thanks;
joe b.

[floodgate]

Joeb:

"You and your sources should differentiate between HEAT and TEMPERATURE. Heat is a quantity, like a pound or a kilogram. A certain amount of heat will raise the temperature of a mass of EX water by a number of degrees."

Another way of saying this is that Temperature is an "intensive quantity", while Heat is an "extensive quantity". Temperatures are not additive; heat is. There is ONE exception, though, as anyone who has indoor cats well knows. A cat's normal body temperature is 101.5F; three cats are three times as hot, at 304.5F, especially when they curl up with you on a hot summer night. Ask Catpetman.

Sorry!

Doug

[Tiger]

Ralf;
First you and your sources should differentiate between HEAT and TEMPERATURE. Heat is a quantity, like a pound or a kilogram. A certain amount of heat will raise the temperature of a mass of EX water by a numkber of degrees. A calorie raises a gram of water a degree C. A calorie is a quantity of heat.
Temperature is a measure of ~ intensity~, like speed. Something at 5000 degrees C,hot, but depending on the mass may not contain much heat. A lit match may hhave a high temperature, be hot, but doesn't contain much heat.
So the HEAT doesn't exceed the melting point of the barrel, the TEMPERATURE does. Since the HEAT isn't sufficient to raise the temperature of the barrel to the melting point, no melting.

Second; everything I know tells me that my gun barrels heat up at te chamber end first. My guns, over many years. Not at the muzzle.

Third, I suspect that friction makes little of the heat in the bullet. Yesterday the idiot next to me shot his M1 and the brass landed on my bench. That brass is HOT!!! I made him go away. From an autoloader, brass is HOT, the temperature is high. From a bolt gun, the brass is NOT HOT, unless the operator is very fast. The brass gets hot from the burning gas. If it comes out of the gun quick, it stays hot. If it stays in the chamber of a bolt rifle, it cools down quick. I take each case out of the rifle and wipe it off, bolt gun. I don't ever remember a hot case. But I shoot lead, slow, and take my time. Maybe a fast jacketed fast operator will experience hot brass
Anyhow, if the brass gets hot, the bullet gets hot. The AREA of the bullet base is much smaller than the area of the case inside, but I'm suspecting that the bullet gets hot from the gas mostly, friction less. I'm not having much luck figuring the heat gained from friction of the bullet.

Fourth, if you want to understand the bullet tempperature measurement, go the the site. It's there, and their experiment.

Summore: The velocity is NOT always greatest at the muzzle. (22 RF, 48" barrel; some of my loads, see the whole plinker/subsonic business) Friction bore/bullet is NOT greatest at the muzzle. Bullet is completely sized to the barrel.

Please be careful, apply your critical faculty before posting.

Thanks;
joe b.

Joe

I do not know why you say this to me. How stupid do you think I am to not know the difference between temperature and heat. Here is better explanation of temperature: The temperature of a body is it's thermal state considered with reference to it's power of communicating heat to other bodies.

I read the website you got the heat of 5.56 bullet from. You notice last line say: The bullet gets very hot as it is forced down the rifle barrel at supersonic speeds. This can be thought two ways but to me looks like they hint friction.

I believe you to be very wrong about empty brass temperature between manual action and semi action rifle ejection. I have seen many instances neck sized only cases ejected from normal commercial semi action hunting rifle that 2/3 case turn dark blue from both powder and friction heat. Same rifle fire factory munition and case not change colour and not nearly so hot.

Ralf

[runfiverun]

brass is a very good heat sink it has been predicted it will get to 400 deg or a bit
more when in the chamber it also cools quickly.
maybe this is why it is a good fit here as you need to get it 600 deg or a bit more to anneal it.
good thing too as we would not be using brass if we annealed the whole case when we fired it.
with a semi-auto it is flung out of the chamber while still hot.
remember that when shooting a bolt action you gotta take your hand off the stock and
function the bolt. this is plenty of time for the brass to transition and start to cool.
whereas the semi already has a new round in the chamber.
even at the speed the semi works the pressure has dropped enough for the case
to let go of the chamber walls to be ejected.

[Tiger]

brass is a very good heat sink it has been predicted it will get to 400 deg or a bit
more when in the chamber it also cools quickly.
maybe this is why it is a good fit here as you need to get it 600 deg or a bit more to anneal it.
good thing too as we would not be using brass if we annealed the whole case when we fired it.
with a semi-auto it is flung out of the chamber while still hot.
remember that when shooting a bolt action you gotta take your hand off the stock and
function the bolt. this is plenty of time for the brass to transition and start to cool.
whereas the semi already has a new round in the chamber.
even at the speed the semi works the pressure has dropped enough for the case
to let go of the chamber walls to be ejected.

runfiverun

I do not believe any of this either. If the brass get that hot then why isn't constantly annealed? A good rifleman with good fast smooth action can bolt empty case out pretty fast. Yes not like semi automatic action but still fast that if as much heat as some claim is in brass then it would be much hotter.

I tell you it has lot from friction. Think too towards many semi automatic actions are really extracting when gas pressure has not totally gone. M14 is one good example this. Brass life is not very good in M14 either.

Ralf

[Larry Gibson]

Ralf

FYI; To anneal brass it is plunged into water after heating. Letting it air cool hardens it, just like it does.

It is true that primary extraction begins in an M14 before pressure is gone. Case life is short because of case stretching in the web area during sizing. Using regulr FL dies does result in relatively short case life. However, with RCBS X-Dies dies case life of 7.62 cases can be 16-20+ firings per case.

Larry Gibson

[runfiverun]

my hell tiger it does not anneal as the temp DOESNOT get to the anneal temp.
it does get hot enough to make the case brittle.
maybe that is why my brass for my cast boolits, my m-14, and my hunting rifle all stay seperated,separated whatever.....even if using them in the same rifle.

[leftiye]

Much as I'd like to have things be hot, I've got to say that in the semi autos it looks like high rate of fire is the culprit, and the cases get hot from contact with hot barrels maybe. Do they come out that hot from a cold gun?

Larry, I ignored your crap on the other thread last night. Here is your chance to practice straight answers. Might be good therapy.

[joeb33050]

runfiverun

I do not believe any of this either. If the brass get that hot then why isn't constantly annealed? A good rifleman with good fast smooth action can bolt empty case out pretty fast. Yes not like semi automatic action but still fast that if as much heat as some claim is in brass then it would be much hotter.

I tell you it has lot from friction. Think too towards many semi automatic actions are really extracting when gas pressure has not totally gone. M14 is one good example this. Brass life is not very good in M14 either.

Ralf

Ralf;
What don't you believe? Do you know that brass from an M1 for example is VERY hot? Also from a carbine? If you didn't know this, you should now.
Friction making the brass hot? No. It's the gas, Ralf.
joe b.

[joeb33050]

Much as I'd like to have things be hot, I've got to say that in the semi autos it looks like high rate of fire is the culprit, and the cases get hot from contact with hot barrels maybe. Do they come out that hot from a cold gun?

Larry, I ignored your crap on the other thread last night. Here is your chance to practice straight answers. Might be good therapy.

Lefty;
First shot out of a cold gun, M1 or Carbine. Weren't any of you guys in the military? Don't you remember going to the range and being told to get that collar buttoned? To keep the other guy's brass out.
First shot, too hot to hold.
joe b.

[Larry Gibson]

Larry, I ignored your crap on the other thread last night. Here is your chance to practice straight answers. Might be good therapy.

I already told you to take your questions over to the proper thread. All you want is an argument. You've followed and posted your garbage on threads where it doesn't belong. Either take your football and go home or post properly on my thread where it belongs.

I made my comments pertinent to the topic on the first couple pages. Other than that I've no dog in this hunt. Had you read and been paying attention you would know that. However you childish attempts at baiting me into a long winded argument here fail. Go to my thread to ask your question or go home like a spoiled little boy. Quit ruining others threads with your foolishness, it’s not polite.

Larry Gibson

BTW; Again as stated before; ask a question (on the proper thread) and I'll answer it.

[Tiger]

Joeb

I shot many rifles probably some you haven't. Let me ask this. How many have been resizing and brass is warm after pulling out of sizer die fast? That is slow pull by semi automatic action standards.

Yes I agree that fast shooting and heated up barrel heat brass up. Ever heard of cook offs?

Runfiverun

You better believe brass hot enough to anneal some.

There is for sure much heat put into case both from friction and from powder burning but how much who knows.

Larry

You getting hard time from comrades? Hey I hope Germany not responsible for WW3 with all arguments going on.

Ralf

[runfiverun]

ralf
yes some, but the hardening is from the slow air cool.
if 15 cycles of this plus sizing=30 times untill failure=some i guess that u.r.right.....

[Scrounger]

Quote: However you childish attempts at baiting me into a long winded argument here fail.

Sorry, Larry, they didn't fail, you're still in the argument. By the way, did I point out that it takes two to have an argument? If one quits responding, the argument stops. It's usually a woman thing about getting in the last comment, men are usually brighter than that. They realize they are never going to convince the other person, or shut them up, so they themselves shut up and walk away, salvaging what little dignity, and credibility, they have left. I don't have a side in this dispute, or any interest in it, but the two (three?) of you have carried on this asinine act for almost a month now and frankly it is starting to get annoying. This message is intended for the lot of you, not just you alone. I expect I'll get a quick "Butt out"" from you, and I will just walk away without responding in kind. Really, I just hate to see you destroy the respect and credibility you have built up over the years here in a useless dispute. You can only offer to share the knowledge you have acquired, you can't force people accept it.

[leftiye]

Joe, cool enough. Like I said, my theories would like it to be hot.

Larry, What's the problem now?

[Larry Gibson]

Scrounger

Not trying to argue with leftiye, just trying to get him to ask his question on the right thread. He might just actually have a pertinant question, I'd like to give him the benifit od the doubt. He does avoid it like the plague though. I am about through with him.

Thanks for the thoughtful input.

Larry Gibson

[runfiverun]

the brass thing should be in its own thread anyway.
and by about thread 45 on two twists, leftiye did agree he thought there was
validity to the test.

but larry is right there are three other threads about the subject, and it should be kept in them.
as even through the disagreement there is still alot of information being passed along.
i just wish that leftiye would loosen up with some info. even babore who
was just stepping in provided [is that a word?] more info in one post then i have seen
in at least 50 posts on two twists.

[leftiye]

Run5run,
I'm not at all trying here to agitate Larry. But it actually DID get so frustrating trying to present concepts to Larry and getting non answers - (Just a statement of fact. NOT to be confused with not getting answers that I liked as Larry has said) - that I chose instead to call him on his fallacies. I've got to apologize to all of you for this, as I'm aware that it didn't make for good reading.

[Larry Gibson]

leftiye

As I've told you (how many times now?) ask your questions on my thread and I'll answer. Because you don't like the answers I've given before is the reason you still "agitate". It is obvious to everyone.

Larry Gibson

[joeb33050]

How much does friction heat up the bullet and barrel?
I tapped a 31141 bullet into the bore of my 30/30 bench gun, then tapped and pushed it back and forth in the barrel. It never loosened up; it always had a lot of stiction = static friction. I had planned to use a scale on the rod to get a notion of the force required to move the bullet, but that didn't work. A better setup is required for good readings.
So I did the arithmetic, and made a spreadsheet that would answer the question of how much the barrel and bullet might heat up at various amounts of force.
If it takes 20 pounds of force to move a 170 grain bullet through the 2' barrel, there's 40 foot pounds of work done. (20 pounds is in the ball park, it ain't 2 pounds and it ain't 100 pounds.) This work turns into heat that goes into the bullet and the barrel. Let's say the barrel weighs 6 pounds.
If all the heat goes into the bullet, (and it doesn't), then this work raises the bullet temperature 5190 degrees C.
If all the heat goes into the barrel, (and it doesn't), then this work raises the barrel temperature 6 degrees C.
Somewhere between these two is the increased temperature of both the barrel and the bullet, between 6 and 5190 degrees C.
All if I did the arithmetic correctly.
The workbook is up on the book site; I'm hoping that somebody who knows about this stuff will review my arithmetic and point out the mistakes.

[leftiye]

Joe B.

Not being critical, but there's a LOT of ballpark there. What I mean is (remember that degrees C are about 1.8 degrees F) if this was degrees F instead of Centigrade, and only 1/5 of it went the boolit"s way the lead would be about 1000 degrees F hot! Kinda like taking the most extreme possibility against melting, and still having the lead melt. Maybe if you could find a ppressure scale and push the slug through the barrel you could find the pressure necessary to move the boolit. (Maybe that's what you did and I misunderstood?)

Larry - Nobody cares, you're not running anything.

[runfiverun]

500 deg sounds realistic maybe more if the brass is at 400 or so
add some fricton and 100 more sounds easily obtainable, especially with 40k behind it.

[leftiye]

R5R, that 1000 degrees (if I read Joe's post correctly & etc.) would be before the heat from the burning gasses entered into things. I'm not even guessing that that guestimate is very accurate (1000 F.), nor wanting to defend it - only illustrating what the possibility is.

[runfiverun]

just trying to get a grasp on the friction area,taking into account the lands and grooves
a 224 bullet must have near a 1/2 inch of bearing surface.
then with the linear force of the gas and pitting in the base [p/b] of the boolit
thiswith a 224 boolit again, another wag but 3/8th's inch here
i figure near 7/8 th's of an inch of bearing and non bearing area being heated here.
this kinda ties into my surface hardness thing, if it is able to withstand the heat [pun kinda]
and distortion, to make the trip.

[joeb33050]

I started the arithmetic all over, and got different results plus figured where the temp increase of the bullet and barrel were equal. Here it is


How much does friction heat up the bullet and barrel?
I tapped a 31141 bullet into the bore of my 30/30 bench gun, then tapped and pushed it back and forth in the barrel. It never loosened up; it always had a lot of stiction = static friction. I had planned to use a scale on the rod to get a notion of the force required to move the bullet, but that didn't work. A better setup is required for good readings.
So I did the arithmetic, and made a spreadsheet that would answer the question of how much the barrel and bullet might heat up at various amounts of force.
If it takes 20 pounds of force to move a 170 grain bullet through the 2' barrel, there's 40 foot pounds of work done. (20 pounds is in the ball park, it ain't 2 pounds and it ain't 100 pounds.) This work turns into heat that goes into the bullet and the barrel. Let's say the barrel weighs 6 pounds.
If all the heat goes into the bullet, (and it doesn't), then this work raises the bullet temperature 1221 degrees C.
If all the heat goes into the barrel, (and it doesn't), then this work raises the barrel temperature 1.28 degrees C.
Somewhere between these two is the point of equal increased temperature of both the barrel and the bullet. This point is where the barrel and the bullet both increase temperature by 1.275 degrees C.
It seems to me that the tendency would be toward equal temperature increases; toward the 1.275 degree C increase for both bullet and barrel.
All if I did the arithmetic correctly.
The workbook is up on the book site; I'm hoping that somebody who knows about this stuff will review my arithmetic and point out the mistakes.

[joeb33050]

Joe B.

Not being critical, but there's a LOT of ballpark there. What I mean is (remember that degrees C are about 1.8 degrees F) if this was degrees F instead of Centigrade, and only 1/5 of it went the boolit"s way the lead would be about 1000 degrees F hot! Kinda like taking the most extreme possibility against melting, and still having the lead melt. Maybe if you could find a ppressure scale and push the slug through the barrel you could find the pressure necessary to move the boolit. (Maybe that's what you did and I misunderstood?)

Larry - Nobody cares, you're not running anything.

Maybe someone would measure the force required to push a bullet through the bore. Once it got moving. It's something like 20 lb, for my try. Anyone?
The relationship is involved, see the workbook, sheet called FRICTION.
joe b.

[leftiye]

Joe, Correct, I think the force to keep it moving is what you want. Also, my guess is that the boolit and barrel might each absorb the same amount of heat. This would heat the barrel far less than it would heat the boolit. Much more mass and area in the barrel. Fly in the ointment - would the hot boolit lose heat to the barrel, or would the friction interface slow this down? Time in transit would probly make this very minor whatever happenens. Thanks again for interesting subject matter.

Like you said , maybe someone with some physics background could help with this. Taint me!

[runfiverun]

i ain't no phsicsists either, but i know we got some on here.

[Tiger]

And all this math calculations help what? I suppose laymen cast shooter can make rifle shoot better with pencil. Too much waste Castboolits hard drive.

Why not post loads alloys powders loading technique instead all this figuring.

I like Larrys method better. He does not boggle mind with figures and formulas

Ralf

[leftiye]

Tiger, If we end up demonstrating that the friction can or probably will heat the boolit significantly (near to melting, or enough to make it very soft),een if it's only a very thin layer of the surface, then we've found another reason why Loads might go form accurate to all over heck in a few more fps/psi..

As I've said elsewhere, the evidence suggests that more deformation is happening than the common view of lead (not melting) deformation in the barrel would explain. The paper patched scenario suggests that the lead being insulated from the barrel results in much less deformed boolits. It would lower significantly the rpms necessary to destroy accuracy (if it wasn't already beyond hope when it left the barrel) or disintegrate a boolit. It may explain loads that just never stabilize and are seen as "just bad loads". I'm not saying it does do all of these things, I'm only saying it has possibilities.

At least that's my interest here.

[Tiger]

Tiger, If we end up demonstrating that the friction can or probably will heat the boolit significantly (near to melting, or enough to make it very soft),een if it's only a very thin layer of the surface, then we've found another reason why Loads might go form accurate to all over heck in a few more fps/psi..

As I've said elsewhere, the evidence suggests that more deformation is happening than the common view of lead (not melting) deformation in the barrel would explain. The paper patched scenario suggests that the lead being insulated from the barrel results in much less deformed boolits. It would lower significantly the rpms necessary to destroy accuracy (if it wasn't already beyond hope when it left the barrel) or disintegrate a boolit. It may explain loads that just never stabilize and are seen as "just bad loads". I'm not saying it does do all of these things, I'm only saying it has possibilities.

At least that's my interest here.

Leftiye

If you think that the paper insulate the bullet from heat then look to a change in your lube. I have and made big difference. I see lube as only change to offset friction. I do not think alloy change enough.

Ralf

[runfiverun]

ralf said: Isee lube as only change to offset friction.

this is exactly what i was working on when i deciced to shoot those other tests.
what i have been able to determine is that you are able to see a difference in velocity
at different bbl temps, with harder lubes i have seen higher vel at lower temps.
when temps warmed and the lube got near its flow temp [ like in the lubrisizer ]
it seemed to hold a pretty even velocity string.
when it got hotter it seemed to flow differently, and velocity seemed to drop about 25fps AVE.
this is with just one type of lube though. have just recieved a different type to try this with.

[floodgate]

Hmmm... A few weeks ago, there was some discussion of the super-power, large-bore air rifles that work off 3000 psi dive tanks. Since the heat of compression is bled off as the tanks are charged, and the air starts at room temperature and cools on expansion, you'd have a "cold" propellent, which would contrast with the hot powder gases from ordinary smokeless. It would be interesting to set up a test rig that could fire identical bullets to the same velocity alternating compressed air and powder, and see how the results compare. If you could collect the bullets imediately after impact (crumb rubber trap; hanging swatches of rug samples; or ???) and compare for temperature....

This needs some thinking through, but ought to be do-able, somehow.

floodgate

[joeb33050]

"Garandsrus" on CAST BOOLITS was kind enough to send me a copy of the article "Comet Tails" by Gardner Johnson, from the April 1998 PRECISION SHOOTING.
While I have some problems with the article, Johnson explains that there is a formula for predicting skin temperature of high speed aircraft.
Fiddling with the table of temperatures and velocities in the article, I find the formula to be: Delta T =:Temperature rise above ambient (Degrees F) = V^2(fps)/13310.
Increases to T are:
V(fps) Delta T
500 19
1000 75
1500 169
2000 300
2500 469

In the example of lead/1.5% antimony with a melting point of 600 degrees F, and an ambient temperature of 75 degrees F, the skin of a lead alloy bullet would become liquid at 2646 fps.

The calculated skin temperature falls as bullet speed falls; and that's pretty fast. For example, a .202 BC bullet with 2700 fps mv has skin temperature of 548 degrees F above ambient at 50 yards; and 179 degrees F above ambient at 300 yards when v has fallen to 1545 fps.
It seems unlikely that the center of the bullet reaches anything like the skin temperature.

The article also includes a table of Tensile Strength of lead in temperature. I used this table to construct a graph of Tensile Strength(lb/in^2) vs. Temperature (Degrees F) for lead, WW and Lino.

[joeb33050]

Do Cast Bullets Blow Up?
We have some tools to allow us to look at the question.
A workbook that calculates the velocity (and RPM) where tensile strength = centripetal force = where the bullet blows up; for any combination of caliber/twist/v/tensile strength.
We know that tensile strength of lead alloys falls as temperature rises.
We have worksheets that allow us to calculate the heat and temperature increase to the bullet caused by friction within the barrel and by air outside the barrel. We also have worksheets to calculate skin temperature as a function of v, and alloy tensile strength as a function of temperature.
We have now the ability to make some statements about cast bullet blow up that should be helpful. And the ability to answer questions about if and when a specific bullet/mv/alloy will blow up.
joe b.

[Larry Gibson]

Joe

I agree with Ralf; all this calculating is proving nothing. Has anyone actual blown up a cast bullet in flight? Perhaps some shooting is in order instead of all this "pondering".

A simple test with a fast twist on the order of 1:8" would do it. There are enough 6.5/284s around. That should do it with a light cast bullet. Should do it that is if a cast bullet will blow up in flight(?). A large dirt back stop at 100 yards or so and two observes wouldn't be too hard to arrange. How about you Leftiye? Do you really want to prove something?

But then, silly me, I only run tests and deal with facts. I'm wrapped up in another test (in case no one's noticed;-) or I'd do it.

Larry Gibson

[Tiger]

Larry

Thank you for agreeing with me. I think the test you suggest is good and very simple. Larry you and I already know outcome of such test.

Joeb

The comparison of aircraft skin temperature good except for one thing. That one thing is time. The bullet is not in flight quite so long. I know you accounted for this.

Ralf

[leftiye]

Yes, Larry someone (a couple of them) has blown up a lead boolit. Rockrat blew up a 50 cal at 2600 fps. IIRC, and Richard Lee has blown up 30 cal at approaching 4000 fps. No, I don't want to do it, this is good enough for me.

I see this (Despite Larry's "you can't do anything about twist" perspective, BTW that's what we all told him about RPMs) as being good and useful information that will help us understand boolit deformation in the barrel, and possibly in the air too. What do you suppose 600 degree lead that has been heated by the air does in response to air pressure? It is - due to the temperature - not able (too weak) to resist the pressure. Does it erode?

So how is it a bad thing if we can demonstrate this via mathematics? Or calculate the weakness of lead in the barrel. It's new knowledge (to me anyway), and unless the math is faulty (and it isn't) it's as proven as it can get. At least with our resources.

[Tiger]

Leftiye

No body has blown up cast bullet in normal velocity. Rockrat bullet is exception as Joeb and both figure out with such fast rifling twist the bullet circumference had double the rotation spin in feet per second then average 30 caliber bullet. In other words much more force stress on it. You know too that paper patch bullet reach pretty high velocity with out blow up too. The patch does not provide protection from the air because it leave the bullet at the muzzle.

I agree math too complicated for average cast shooter. What happen soon forum owners require math courses to join forum. All we need is just test where tester find out what velocity and rifling twist cast bullet more likely blow up. As much argue with Larry I have to agree with him here.

Ralf

[leftiye]

Ralf, nobody stipulated that normal velocity was in the question. If "normal" velocity is required, the test is a waste of time, as they won't blow up until you spin them fast enough to exceed the tensile strength of the lead at whatever temp it happens to be (shown by R. Lee to be in the neighborhood of 4000 fps.). So the fast twist of Rockrat's rifle was legitimate, it was after all a production rifle. And if twist is necessary to tear a boolit apart a Gibson type of measurement of rpms is the method (as was done for Rockrat's example), and fast twist only helps you to get there. BTW, I never completed trig. in high school. But I can do the arithmetic, and can see what arithmetic needs doing.

[runfiverun]

ralf and leftiye
did i just read that coorectly that you both said rpm's [ well revolutions and spin them fast enough]
are going to negetively affect a boolit?
oooohhhhh.

[leftiye]

R5R, That's a good Larryism if I ever heard one! yeh, I guess ya could say that blowing up would be a "negative" ocurrence for a boolit. LOL

[Larry Gibson]

Runfiverun

I caught that too! Leftiye just hates it when he gets caught with his foot in his mouth. Lefteye still hasn't figured out that the lead of bullets doesn't melt from air friction. The time of flight is too short. Talk all you want about airplane wings, etc. but remember they take a lot longer getting to that speed and then heating up than a bullet is in flight. Also remember the bullet slows down very quickly and the airplane doesn't.

Leftiye also still hasn't answered as to why bullets from the .220 Swift and other cartridges with velocities of 4,000+ fps don't melt. Yet he thinks/claims "What do you suppose 600 degree lead that has been heated by the air does in response to air pressure" insinuating that cast bullets get hot enough to melt. Bunk. They blow up just like jacketed bullets with thin jackets that are pushed to high velocity/RPM. Yes bullets get hot from friction and the burning powder behind them but they in no way get hot enough to melt. They come apart because the tensile strength of the alloy is over come by the centrifugal force. It's that simple.

Leftiye is just leading you down another merry path with something that doesn't matter. I'm still waiting for Leftiye to post about something in the business of cast bullet shooting that he has actually done. He yaps a lot but have we seen any groups, tests or anything from him? No we don't, all we get is abstract opinions and concepts that mean nothing.

Joe was on the right track proving it mathematically before you all went off on a tangent about heat, friction and bullets melting in flight. This was a good thread then and looked promissing. With the track that it has taken it is not going anywhere (much like another thread where leftiye continues with ideas and questions that mean nothing - his words actually). Joe, why don't you get back on track about what really does cause bullets to blow up. It would be neat if you could compute when that would happen with a certain alloy and then conduct a test to see if the math equals reality.

Larry Gibson

[leftiye]

Yeah, I really hated that LOL.

When one stipulates as Joe did that he was calculating the amount of RPM necessary to tear apart a boolit, That's what you discuss. Every one but Larry, that is. Larry what's this problem of yours in coming on an open thread and assasinating me with your crap? Did someone tell you it was open season or something? Didn't see any facts mixed in with your manure. FWIW

[Larry Gibson]

Leftiye

Your question in your own words; "Larry what's this problem of yours in coming on an open thread and assasinating me with your crap?"

The answer in your own words; "Despite Larry's "you can't do anything about twist" perspective" and "That's a good Larryism if I ever heard one!"

You asked for the answer, you got it.

The facts are well known, Bullet flight time is very short. Time for airplane to get up to speed to heat wings to a high degree is a lot longer than a bullets flight time. Bullets also slow down very quickly, airplanes don't. Bullets don't heat up enough from air resistance during flight to melt. Those are facts. I was shooting cast bullets today at 2500 fps and none melted, that is a fact. I shot 20 shots out of my 22-250 at 3650 fps today and none of the bullets melted, that is a fact. Bullets don't melt from air resistance and that is a fact. They may come apart from centrifugal force of RPM, that is a fact. You keep dreaming wierd nonsensible crap up, that is a fact.

Larry Gibson

[Larry Gibson]

Joe

I apologize for this intrusion but I saw your thread going the way mine did with Leftiye. Stick to your original thoughts on this, they were correct. I'd like to see it proven mathematically so we can test it in reality. Thanks for your effort here.

Larry Gibson

[leftiye]

Yeah, Larry, we were having so much trouble getting along . Thanks for coming along and making things so much more pleasant. Thanks also for straightening us out on so many concepts that we just aren't equipped to handle without your taurine excrement. We're all back on the straight and narrow now, you can relax now. That's a fact.

[leftiye]

[The answer in your own words; "Despite Larry's "you can't do anything about twist" perspective" and "That's a good Larryism if I ever heard one!" You asked for the answer, you got it.] Larry Gibson

So you're going to have a Manure Hemorrage every time your name is mentioned? I thought only Himself got to worry when his name was taken in vain. Oh, I FORGOT!

I can't even be friendly with RunFive Run about a comment he seemed nervous about making without you exploding all over everything? I can't even quote you without you punishing me for it? Did you get up on the wrong side of the bed? Poor Baby!

[waksupi]

OK, you guys have been bickering long enough. Knock it off. Now.

[runfiverun]

i feel like the only guy at the fight out by the flag pole where one conrestant
is his friend and the other is the one he bet money on.

[Larry Gibson]

Dang....and all I wanted to do was try to blow up cast bullets following Joe's mattematical solution.

Larry Gibson

[runfiverun]

i wanna make some poofs too.
but for some reason all my rifles only hold 50 grains of powder or less.