Applied Ballistics for Long Range Shooting by Bryan Litz

[45 2.1]

Here, for your perusal are articles by Bryan Litz, whose book and articles are at least part of the basis for an unproven theory so popular on this site. You will note that all of these are for jacketed bullets shot at farther distances and a lot high velocity than you shoot your own cast boolits. You can decide for yourself whether what you have seen in print here matches what's written in the articles on the following site (which are downloadable PDF files). Good reading to you................

Link: http://www.appliedballisticsllc.com/Articles.htm
where the following articles are:
Part 1: The Nature of Scale & (http://www.appliedballisticsllc.com/index_files/Understanding_part1.pdf)Part 2: Practical Considerations and Decision Making (http://www.appliedballisticsllc.com/index_files/Understanding_part1.pdf)

[Larry Gibson]

When you read those articles pay close attention to Litz' explanation of Epicyclic Swerve as that applies to cast bullets as well as to the very excellent quality and balance match bullets Litz is discussing.

Unfortunately, since quality of the bullets Litz discusses is assured, He does not address what the adverse effects of bullet imbalance has on the bullet in flight. You have to look in other ballistic references for that information.

Larry Gibson

[swheeler]

If only we could Juenke(sp) all our cast bullets we wouldn't have to worry about it, if only. Could you imagine the rejection rate of cast bullets on one of these machines:0

[45 2.1]

Here you go folks, the link to epicyclic swerve:

http://appliedballisticsllc.com/epswerve.html

Conclusion: a very minor event, you would do better learning to dope the wind well.

[303Guy]

That's interesting. There's a video someone posted a link to in which the fellow damaged 22lr bullet noses in different ways to see the effect. The video clearly showed the spiral flight path of those damaged bullets. One could see that with some damaged bullet noses the spiral path was not cone shaped but more cylindrical. In those cases the angle of shot dispersion over distance would diminish. The radius of the spiral was way more than a few calibers too.

[Larry Gibson]

303Guy

One could see that with some damaged bullet noses the spiral path was not cone shaped but more cylindrical. In those cases the angle of shot dispersion over distance would diminish. The radius of the spiral was way more than a few calibers too.

Those were of the helical arc I and others (including professional ballisticians) refer to. They are a different phenomena than the Epicyclic Swerve Litz refers to. That which Litz refers to is caused by the nose lift (as mentioned in his synopsis). The helical arc referred to in those video's is caused by the induced imbalance artificially put in the .22LR bullet acted upon by the RPM (centrifugal force). A .22LR bullet at 1200 fps out of a typical 16" rifle barrel will have only about 54,000 RPM. Thus the rotational stability of the bullet can over come the arc and we see the arc diminish. However, increase the RPM to 140,000 RPM (top end of the normal RPM threshold) and the helical arc would get bigger, not smaller. The test is easily accomplished with a 16" twist 22 Hornet using the 225438 or the 225107 by inducing the same imbalance to the bullet and pushing that imbalanced bullet from 1000 to 2800 fps.

Here is the similar test I did for Bass Ackward way back when using a 311291 loaded under the RPM threshold and over the RPM threshold. 10 shot groups were fired at 50 yards, 100 yards and 200 yards. Note the linear expansion of the groups as range increases with the load under the RPM threshold. Then note the very non-linear expansion with the load that was over the RPM threshold of the groups as the range increases. The bullets of the over the RPM threshold load did not 'go to sleep" and none of the groups got smaller....they got larger, considerably larger. That is because the RPM induced a sufficient centrifugal force acting upon the induced imbalance of the bullet that the rotation stability of the bullet could not over come it. Thus accuracy got progressively worse due to the increasing helical arc.

Load under the RPM threshold at 50, 100 and 200 yards;

92743

Load over the RPM threshold;

9274492745

The targets show the results. I've requested 45 2.1, geargnasher, goodsteel and others on this forum to conduct this simple test numerous times so they would easily see the cause and effect. They don't seem to want to, just want me to "give it up"......well the targets (facts) speak for themselves.

However, Mr. Litz is entirely correct in his dissertation. It applies to very well made and balanced jacketed bullets. It also applied to saboted and PP'd cast bullets (the sabot and PP are a "jacket" also) up to a point. Mr. Litz's very fine dissertation however does not apply to cast bullets that are pushed above the RPM threshold. The above targets demonstrate that clearly.

Larry Gibson

[vintagesportsman]

Epicycle is not an issue unless there is a problem with the barrel. Much like a quarterback. When a good throw is made and there is correct form the ball will spiral to its target. A bad throw will begin tightly and end erratically - epicycle in its basest explanation. Some rifles have more issues than others. Some are sub-moa to 100, 200, 300 but after three hundred they do not throw the ball well. Others can chuck the "Long bomb" for a touchdown to 1000 yards and have little to no epicycle. Sure, there may be bad balls, but mostly bad barrels IMHO...

[Larry Gibson]

Sure, there may be bad balls, but mostly bad barrels IMHO...

If the crown is good the "bad" is most often the wrong twist for the bullet...........

Larry Gibson

[vintagesportsman]

Exactly, by bad I do mean other than "damaged". There are so many variables involved. What I do not understand is what is "High lift co-efficient"?
Sure, there may be bad balls, but mostly bad barrels IMHO...

If the crown is good the "bad" is most often the wrong twist for the bullet...........

Larry Gibson

[45 2.1]

Gentlemen...... this is not a soapbox. Let the articles be compared to what has already been posted. If you want to discuss something....... Start your own thread.... that is unless you're afraid things said here will undermine/damage your stated position, in which case you will have probably already established that fact by continuing interjecting statements.

[btroj]

Here you go folks, the link to epicyclic swerve:

http://appliedballisticsllc.com/epswerve.html

Conclusion: a very minor event, you would do better learning to dope the wind well.

I can't think of many things more important to becoming a good long range shooter than learn ing to dope wind well. That is what separates a great shooter from a great trigger puller.

[Larry Gibson]

Gentlemen...... this is not a soapbox. Let the articles be compared to what has already been posted. If you want to discuss something....... Start your own thread.... that is unless you're afraid things said here will undermine/damage your stated position, in which case you will have probably already established that fact by continuing interjecting statements.

I'm certainly glad you've interjected that 45 2.1.....makes perfect sense to me and is something I'm sure we can all agree to adhere to, especially on threads started by others.........like my 6.5 Cruise Missile test thread.........:roll:

I'm also very glad to see you've proffered some excellent information by a ballistician like Mr. Litz in his writings/articles you've posted here......so everyone take note that Mr. Litz coorectly states (and 45 2.1 has posted it here for us so he obviously agrees with it:-D);

Understanding Long Range Bullets
Part 2: Practical Considerations and Decision Making
By Bryan Litz

Practical Consequences of Stability

Page 9........The second consequence of high twist rate has to do with accuracy
.potential.. Some major factors affecting dispersion are related to the spin rate of
the bullet. Jacket eccentricity and in-bore yaw are two examples. These types of
dispersion are directly related to the RPM of the bullets, which increases with
twist rate and velocity. Twist and velocity are two things you need a lot of to be
competitive with smaller calibers, and can exacerbate certain types of dispersion.

That is exactly what I have been telling 45 2.1, geargnasher, goodsteel and several others here for several years now. I find it humbling that 45 2.1 has bothered to read and post the information from a ballistician that in every way agree with what I have been saying. Thank you 45 2.1....welcome aboard :guntootsmiley:

"Twist and velocity are two things you need a lot of to be competitive with smaller calibers, and can exacerbate certain types of dispersion" is exactly where in the RPM threshold falls in relation to cast bullets. The test targets I posted above show exactly that.

Thanks again 45 2.1 for bring this to every one's attention.

Larry Gibson

[MBTcustom]

It seems there is no thread that the RPM theory cannot be inserted into.
I also don't see how specific tests with a specific rifle and a very specific shooter and caster has to do with anything. R5R just posted the other day about screaming cast boolits out at 2700FPS blowing past the RPM threshold like a like a Ferrari past a unicycle.
Some can shoot fast boolits and some can't. Why is that such a bone of contention? My neighbor can box circles around me, because he's built for it and has studied it since he was a kid (I swear that dude has arms as long as my legs!). For some reason, I feel no need to go try to convince him that Muay Thai is all he should love or discipline himself with because that's all I can beat him with. Never crossed my mind.

Thanks for the info Bob. Interesting reading.

[Larry Gibson]

Goodsteel

The point is we can demonstrate the RPM threshold with cast bullets in just about any rifle with a 14" twist or faster if the bullets can be safely pushed to 2700 fps. That the RPM threshold can also be pushed up by some methods in those same very rifles is well understood by me and many others. Apparently you have bought into the RPM threshold as being a "limit" of sorts? It is not and I have explained that to everyone here and to you many times. If we understand the RPM threshold and when it happens then we can deal with it and push it up just as 5R5 apparently has.

I would certainly like to see 5R5s AR do that and know exactly what the loads are. I don't discount that at all as I just recently posted a 2750 fps 10 shot group at 100 yards with a .308W using the 311465. So the RPM threshold can be pushed up, what's new? Some time in the future I look very much forward to shooting with 5R5.

The real point here is 45 2.1 threw out the gauntlet. He could have just posted the sites and let it go at that. But he didn't. He just had to post;

"Here, for your perusal are articles by Bryan Litz, whose book and articles are at least part of the basis for an unproven theory so popular on this site. You will note that all of these are for jacketed bullets shot at farther distances and a lot high velocity than you shoot your own cast boolits. You can decide for yourself whether what you have seen in print here matches what's written in the articles on the following site (which are downloadable PDF files). Good reading to you................"

Seems he opened it up for discussion with that bait.........this is, after all, supposed to be a forum is it not? Is not a "forum" supposed to be (as defined in Webster) "A medium of open discussion or expression of ideas? Or are we to just agree with each other w/o any discussion? 45 2.1 has brought information forward from a respected ballistician and authority that is oft quoted. Where, except for his last post, does he insinuate no response or discussion allowed on his thread? I saw none did you?

Besides, appears 45 2.1 and I seem to agree. Or he failed to state his position?

Larry Gibson

[Digital Dan]

Well, I'll try this a second time. Through the magic of out of control fingers...

This website has a lot going for it and I am being quite sincere. It also has an average share of those sharing opinion easily interpreted as fact by the neophytes among us. The three disciplines of ballistic science are very complex places for a brain to visit, and often very counter-intuitive. We have discussion above about epicyclic swerve and links to a learned fellow who pretty much knows which way north is, but as they say, you can lead a horse to water....

Let me know when we're ready to discuss tricyclic and quadracyclic precession modes. OK, I'm sort of being a wise acre, but they are potentially real factors in a bullet's flight.

Anyone looking for literature on the topic of external ballistics could do worse than read works of the following authors.
Dr. Franklin Mann
Gen. Julian Hatcher
Harold Vaughn
Robert McCoy
Brian Litz (linked above)
Robert Rinker

Rinker's work is presented in lay terms and though quite thick as paperbacks go, it delves into the three disciplines and I will give him high marks for making the information comprehensible to the average person. He does commit a few gaffes but the are not of consequence. Litz has the same presentation style but limited to exterior ballistics so far as I know.

In case you didn't know, exterior ballistics is the foundation of orbital mechanics.... -evil laugh- ...it's really so easy a caveman can do it.

In any case I find exterior ballistics the easiest to quantify because a bullet's flight can be observed directly and indirectly. Interior and terminal ballistics are on the dark side of the moon and rife with variables that hurt my noggin'.

[swheeler]

I'm certainly glad you've interjected that 45 2.1.....makes perfect sense to me and is something I'm sure we can all agree to adhere to, especially on threads started by others.........like my 6.5 Cruise Missile test thread.........:roll:

I'm also very glad to see you've proffered some excellent information by a ballistician like Mr. Litz in his writings/articles you've posted here......so everyone take note that Mr. Litz coorectly states (and 45 2.1 has posted it here for us so he obviously agrees with it:-D);

Understanding Long Range Bullets
Part 2: Practical Considerations and Decision Making
By Bryan Litz

Practical Consequences of Stability

Page 9........The second consequence of high twist rate has to do with accuracy
.potential.. Some major factors affecting dispersion are related to the spin rate of
the bullet. Jacket eccentricity and in-bore yaw are two examples. These types of
dispersion are directly related to the RPM of the bullets, which increases with
twist rate and velocity. Twist and velocity are two things you need a lot of to be
competitive with smaller calibers, and can exacerbate certain types of dispersion.

That is exactly what I have been telling 45 2.1, geargnasher, goodsteel and several others here for several years now. I find it humbling that 45 2.1 has bothered to read and post the information from a ballistician that in every way agree with what I have been saying. Thank you 45 2.1....welcome aboard :guntootsmiley:

"Twist and velocity are two things you need a lot of to be competitive with smaller calibers, and can exacerbate certain types of dispersion" is exactly where in the RPM threshold falls in relation to cast bullets. The test targets I posted above show exactly that.

Thanks again 45 2.1 for bring this to every one's attention.

Larry Gibson

Exactly, couldn't of said it better myself! Hey that is EXACTLY what your targets show with increasing vel/RPMs Larry

[Larry Gibson]

Dan

Litz does say;

"I don.t want to get into a discussion about case volume and powder
efficiency here because I.m frankly not that knowledgeable about it. Besides, this
is about external ballistics, not internal.

Some have a hard time differentiating the two also.

Larry Gibson

[MBTcustom]

Goodsteel

The point is we can demonstrate the RPM threshold with cast bullets in just about any rifle with a 14" twist or faster if the bullets can be safely pushed to 2700 fps. That the RPM threshold can also be pushed up by some methods in those same very rifles is well understood by me and many others. Apparently you have bought into the RPM threshold as being a "limit" of sorts? It is not and I have explained that to everyone here and to you many times. If we understand the RPM threshold and when it happens then we can deal with it and push it up just as 5R5 apparently has.

I would certainly like to see 5R5s AR do that and know exactly what the loads are. I don't discount that at all as I just recently posted a 2750 fps 10 shot group at 100 yards with a .308W using the 311465. So the RPM threshold can be pushed up, what's new? Some time in the future I look very much forward to shooting with 5R5.

The real point here is 45 2.1 threw out the gauntlet. He could have just posted the sites and let it go at that. But he didn't. He just had to post;

"Here, for your perusal are articles by Bryan Litz, whose book and articles are at least part of the basis for an unproven theory so popular on this site. You will note that all of these are for jacketed bullets shot at farther distances and a lot high velocity than you shoot your own cast boolits. You can decide for yourself whether what you have seen in print here matches what's written in the articles on the following site (which are downloadable PDF files). Good reading to you................"

Seems he opened it up for discussion with that bait.........this is, after all, supposed to be a forum is it not? Is not a "forum" supposed to be (as defined in Webster) "A medium of open discussion or expression of ideas? Or are we to just agree with each other w/o any discussion? 45 2.1 has brought information forward from a respected ballistician and authority that is oft quoted. Where, except for his last post, does he insinuate no response or discussion allowed on his thread? I saw none did you?

Besides, appears 45 2.1 and I seem to agree. Or he failed to state his position?

Larry Gibson

The thing is, I'm tired of tripping over a feud when I'm trying to learn, and I'm tired of opinionated people that I respect very much throwing their dirty laundry in my living room.
SO the way this will work is that when somebody posts a thread, that supports their views, they are going to be free to post those views without there being a fight started because of it. Or an overwhelming flood of cronys jumping in to help them beat the point home.
It's no secret the difference of opinion that is present here. If Larry Gibson posts a thread, then I'm going to pound anybody who starts throwing innuendoes and poking the bear. The same goes for Bob's threads, or anybody else's.

It's time for this feud to be over, and I can fix it real easy by kicking all offending parties off the forum.
This is a place to learn and you can't do that if you can't follow a path for a while without getting in the middle of a fight.
It's childish, it's uncouth, it's not necessary, and it's going to stop.

I do not discount the knowledge and expertise either of you have to offer, but it's hard to have respect for people who use knowledge like a club to beat on other people, all while bystanders are trying to learn and not get sucked into "If you're not with us you're against us!" attitude.

[Digital Dan]

And I overlooked a major point, sorry.

It is important to understand that the more esoteric aspects of exterior ballistics are of no great significance to what I perceive as the average bullet caster, which I consider myself to be. Most of us are not shooting long range or pursuing high velocity. Soft alloys well fabricated are cheap to produce, generate fine accuracy and kill stuff as well as jacketed bullets so far as I can tell. What is different about them as a result is the velocity realm where they are used. 800-1900 fps or so seems fairly common. What is significant in that realm is the transonic range of velocity and the drag penalties associated therein. It affects wind drift a lot when a bullet is cruising through the Mach .8-1.2 velocity range,so that is important to cast bullet shooters and perhaps more pointedly, users of black powder cartridge guns.

My .02 cents worth, and you are now returned to normal broadcasting.

[popper]

So the typical yaw of a boolit is not really important to us. Evidently tail heavy or nose heavy doesn't matter either. I don't understand why we don't use power law ogives for better transonic performance. As for the video, understand it is still gyro action that causes the sudden, drastic change in direction.

[geargnasher]

The thing is, I'm tired of tripping over a feud when I'm trying to learn, and I'm tired of opinionated people that I respect very much throwing their dirty laundry in my living room.
SO the way this will work is that when somebody posts a thread, that supports their views, they are going to be free to post those views without there being a fight started because of it. Or an overwhelming flood of cronys jumping in to help them beat the point home.
It's no secret the difference of opinion that is present here. If Larry Gibson posts a thread, then I'm going to pound anybody who starts throwing innuendoes and poking the bear. The same goes for Bob's threads, or anybody else's.

It's time for this feud to be over, and I can fix it real easy by kicking all offending parties off the forum.
This is a place to learn and you can't do that if you can't follow a path for a while without getting in the middle of a fight.
It's childish, it's uncouth, it's not necessary, and it's going to stop.

I do not discount the knowledge and expertise either of you have to offer, but it's hard to have respect for people who use knowledge like a club to beat on other people, all while bystanders are trying to learn and not get sucked into "If you're not with us you're against us!" attitude.

By God it's about time.

BTW, I can settle this RPM thing quite easily: Larry, insofar as he has defined and proven the RPM Threshold Theory is correct. Richard Lee, insofar as his BHN/peak pressure theory is defined and practiced, is also correct. Neither of these concepts is necessarily all-inclusive, as anyone who has well-exceeded the theoretical RPM threshold or accurate PSI-per-BHN threshold (respectively) can certainly attest. Those theories are guidelines one can choose to stay within (simple, easy) or push far past (much more difficult, but to some, much more useful and rewarding than operating from a concept that is by definition, rather limiting).

Now, if ALL of us are free to discuss these things respectfully, without being lambasted and trolled, you can consider me "back". Others might come back and contribute, too, if the BS stops. In keeping with the fair, now if Larry gets a locked sticky with his ideas in it, how about Bob gets one too?

Gear

[MBTcustom]

We make stickies out of posts that are pure of heart, rich of content and short on BS.
I would like to see both viewpoints lauded on this site.
I don't know everything there is to know about these two points of view, but I want the people of this site to be free to examine these things and take their education as far as they would like to go without running into a toxic attitude, which is a total killjoy.
If somebody comes along that likes to shoot Zink boolits no faster than 800fps, and that is their passion, I want them to feel free to post their research and sources, as well as discuss their method with like minded members, without getting the same gang of five members come in and do their best to undermine their work, bash their research, and throw proverbial rocks.

I'm not asking anyone to give up on their position one iota. You worked hard to come to the conclusions you have, and you deserve to be able to write about it. I am saying that I'm going to play whack-a-mole with certain avatars if they keep posting inflammatory things. If you think I haven't been paying attention to the little code language that is used here you've got another think coming. You're not flying under the radar, in fact, you're leaving muddy footprints all over my floor.
All I'm asking you to do is wipe your feet at the door, or stay outside. That goes for members on both sides of the fence!

[35 shooter]

Just a newbie's point of view (joined in june)but i've learned a ton on top of what i already knew, or thought i knew, after joining this site from just about everyone here. I've seen a bit of passion and challenge issued back and forth every now and then but i understand that when when standing behind one's convictions. I think most of us cut through that pretty easily and just look at the facts presented by the different trains of thought and go from there. At least i know i do.

45 2:1 made a post on duplex loads for example the other night that helped me understand it in a way i never had before. On top of that he listed a reference on it to help understand it more.(Thanks so much!). Now i may try something like that in the near future after a bit more research to maybe beat this rpm thing a bit in my particular rifle.
Also was reminded of the rpm threshold by Larry Gibsons posts among a ton of other things he's posted on. And yes i had read about it years ago in some long forgotten article somewhere. He freely admits it can be passed and is just a spot where average boolit loading techniques are going to begin to run into a bit of trouble to get by it. I for one have found that to be true in my efforts. Still gotta lot to learn. I just call it the WALL! Can't seem to get there from here.lol! 45 2:1 says he's done it, Larry Gibson and others too and i have no reason to doubt them.
I respect your job as a MOD goodsteal and understand your stance...just hope no one here gets hurt from any of this. You seem to be a thinker and a fair minded man though.

BTW goodsteal, i'm looking very forward to you getting that rifle built for this spring and your experiments on the rpm thing. I can tell from your posts you know a bit about precision in rifles and loading too...... outta be good stuff!:grin: Just wish you were doing it with a 35 whelen!:(

[303Guy]

OK, I'll come back too. Can someone explain the difference between a spiral bullet path and Epicyclic Swerve please?

It is (or was) well known that the SMLE target rifle would print tighter groups down range than close up. I don't know whether the group sizes became smaller or the minutes of arc became smaller. From my readings it appears that a bullet can and sometimes does have a dual spiral path. I also have read that Doppler radar bullet velocity measurements sometimes show a bullet with cyclic speeding up and slowing down. This is from the spiral bullet path as the bullet is arcing down at the end of its trajectory.

Cast pistol boolits have been shown to have this double spiral path (a smaller, faster cyclic motion superimposed on a larger, slower spiral).

[Digital Dan]

a smaller, faster cyclic motion superimposed on a larger, slower spiral.

That is essentially the definition of an epicyclic precession mode (two modes caused by two factors acting as one). The faster cycle results from bullet imbalance and nulls eventually as the bullet will find a new center of rotation once freed from the confines of the barrel. The slower cycle does not null but it's magnitude may diminish, likely will actually, as a function of gyroscopic stability factor (Sg). Litz discusses this in the link provided earlier regarding epicyclic swerve.

http://appliedballisticsllc.com/epswerve.html

For what it's worth, all bullets fired from all guns experience this phenomena without exception, be they jacketed or cast, pistol or rifle. The hook is one of magnitude.

[AlaskanGuy]

I for one am glad that we check the guns at the door...lol, but i love this thread... I have learned a ton, and appreciate the hearty discussion.....

[Love Life]

A thought occured to me this morning (dangerous), but would a gain twist barrel have any influence on the RPM threshold?

Say a 30 cal that starts at 1 in14 and ends in a 1 in 12?

[freebullet]

A thought occured to me this morning (dangerous), but would a gain twist barrel have any influence on the RPM threshold?

Say a 30 cal that starts at 1 in14 and ends in a 1 in 12?

That barrel just sounds expensive, lol. I don't know the answer, but would be interested in it.

[45 2.1]

Here are some other links that will give you some good information.

http://www.riflebarrels.com/articles/bullets_ballastics/bullet_imbalance_twist.htm
http://www.exteriorballistics.com/ebexplained/index.cfm
http://yarchive.net/gun/ammo/bullet_helical_path.html
http://www.shootersforum.com/ballistics-internal-external/66935-question-regarding-over-stabilization-twist-ratios.html

[MBTcustom]

Here are some other links that will give you some good information.

http://www.riflebarrels.com/articles/bullets_ballastics/bullet_imbalance_twist.htm
http://www.exteriorballistics.com/ebexplained/index.cfm
http://yarchive.net/gun/ammo/bullet_helical_path.html
http://www.shootersforum.com/ballistics-internal-external/66935-question-regarding-over-stabilization-twist-ratios.html

Bob, I edited your post to remove inflammatory statements towards Larry Gibson.
My warning goes both ways.
Next, I'm handing out infractions.
Stick to the science and check the drama at the door.

[35 shooter]

A thought occured to me this morning (dangerous), but would a gain twist barrel have any influence on the RPM threshold?

Say a 30 cal that starts at 1 in14 and ends in a 1 in 12?

That was a deep thought for this time of day. Faster twist towards the end of powder burn or push? Now you've got me wondering what it does for accurracy despite what it might do for rpms?

[Love Life]

Bartlein makes gain twist barrels. I've read good things on gain twist barrels, and I was just curious how it would influence things.

In the scheme of things, $350+ for a barrel that would give you TRUE jacketed performance from cast bullets would be worth the money. Of course the cast bullets would need to be up to snuff, but that is on the caster.

[youngda9]

Gain twist with a cast boolit...sounds like a recipe for gas cutting and leading, no?

[Echd]

On the surface common sense would seem to agree, but gain twist barrels are fairly uncommon. I believe S&W has used them fairly recently on some of their high end revolvers- perhaps some of the .460 shooters could give us some input?

Either way, I know some people have used cast in carcanos, although those are not rifles well known for accuracy. They are probably the most well known of gain twist guns, but I'd like to see the results with something a bit more intense, like the 460.

[MBTcustom]

Gain twist with a cast boolit...sounds like a recipe for gas cutting and leading, no?

Exactly
That's the way I understand it. This has been done before (not that the folks doing it knew all the tricks or anything).

[Digital Dan]

There is a fair bit of debate on gain twist theory. The idea began in the era of black powder competition and is fairly common in bullet guns and Schuetzen rifles. A gentlman named Rich Hicks was a champion of the idea and made more than a few barrels for heavy BP bench guns. He won several national titles with such guns. It may also be of interest that the 16" guns on WW2 battleships used gain twist barrels.

The NVA found the guns of the New Jersey depressingly accurate at long range.

YMMV

[swheeler]

Weren't the colt revolvers of the mid 1800's gain twist rifled?

[dverna]

I sincerely hope that spirited discussion is not going to be outlawed. There is nothing wrong with people disagreeing if it is done without personal attack. I guess I have not seen it - or maybe I am thick skinned.

I like to see differing points of view but the one who can back up his opinions either with test data or facts has a big edge in my book. It is part of the learning process as far as I see it.

Many experienced and talented people on this site do things I will likely never do - ie duplex loads. Even though thousands of rounds have been shot without incident, I am not comfortable with the concept. That does not make them wrong - neither does it make me wrong. I still want to learn about duplex loads even if, at this moment of time, I am not willing or ready to try them.

When very knowledgeable, experienced and intelligent people have differing positions we should hear them and question them so we can challenge our little grey cells and make a small step to greater understanding. I for one, find these types of threads so much more interesting than "My 9mm leads", "Look at my purdy boolits", "Bought a new rifle" or the other "fluff" threads.

A little "conflict" is actually a good thing. Without conflict, the Roman Catholic church would have still had us believing the earth is flat. Exiling the Galileo's and Copernicus' amongst us for the sake of harmony is short sighted and wrong - IMHO.

Don Verna

[Love Life]

Gain twist with a cast boolit...sounds like a recipe for gas cutting and leading, no?

How? the only thing that changes is twist, not dimensions. Once the boolit engages the rifling, it is engaged isn't it?

Gain twists are being used for very accurate rifles shooting jacketed. I know what applies to one does not translate to the other, but if if accuracy can be found with one then why not the other?

[303Guy]

One of the US barrel makers used to make gain twist barrels but stopped doing it because they found no advantage. For cast there might be an advantage in so far as there would be less rifling skid on boolit entry into the bore while pressure is highest. The induced skid as the rifling land angle changes would be very small and may be no greater than natural skid which is unnoticeable. The forced skid would occur down the bore where pressure is lower.

On corkscrew motion, Litz says this;
Epicyclic swerve is the technical term for the corkscrew path that a bullet flies as its nose precesses around the flight path. I did I read the first time and is exactly what I'm talking about. Interesting that Litz couldn't get a pronounced corkscrew motion on paper. The SMLE is supposed to produce a pronounced corkscrew. I wonder how many 2 to 3 inch at 100 yds rifles are never tried at 200 or more because they 'wouldn't hit a barn wall' when they might in fact shoot the same 2 to 3 inch groups at 300? What I didn't see was whether Litz was using a spitzer form only or not.

I saw many years ago a bullet drag illustration showing drag at various point on the bullet. The example was a semi-round nose of the 9x19 FMJ type bullet. The nose section had a negative drag or 'forward lift' while the base had a strong positive drag. That would have been subsonic.

I've watched air gin pellets wobble down range until they hit their target. I'm talking smooth bore here.

[texassako]

Bartlein makes gain twist barrels. I've read good things on gain twist barrels, and I was just curious how it would influence things.

In the scheme of things, $350+ for a barrel that would give you TRUE jacketed performance from cast bullets would be worth the money. Of course the cast bullets would need to be up to snuff, but that is on the caster.

Someone could even test it if they had both a gain twist and normally rifled 6.5x52 Carcano.

[Love Life]

I'm interested. I'd like to see the theory proven or disproven.

From what I have read so far: The RPM theory exists and has been semi-proven by Larry Gibson. The only reason I say semi-proven is because on another thread it was discussed that the quality of the rifle and the quality of the boolit have alot of influence as well. It was stated that the RPM threshold could be raised with near perfect boolits and a quality rifle.

In other threads I see members with above average rifles (trued actions, good stocks, better barrels) get pretty solid accuracy off the bat with boolits without having even considered the RPM threshold.

The 1 in 14 30-06 thread and Waco's powder coat thread come to mind.

So what is really more important? The boolit or the rifle? I don't think the rpm theory can truly be tested with a ho-hum rifle.

I'm willing to put my money where my mouth is. I'm willing to go in halfsies on a big name barrel if anybody is willing to play along. Tim can do his part on building his rifle.

I really want to know, as the variables put forth really make it hard to pin it down to RPM's alone. Scientific method here. My hypothesis is the build is the most important part, with the twist coming in second place (within reason).

[45 2.1]

So what is really more important? The boolit or the rifle? I don't think the rpm theory can truly be tested with a ho-hum rifle.

Neither to your what's most important question. It has already been tested in several commercial and stock military rifles........... conclusion... the RPM theory is wrong for the reason it proposes, it's something else altogether (also stated in Litz's articles).

[popper]

epicyclic precession mode - Caused by aerodynamic forces, not imbalance or RPM effects. Also called nose steering. Remember all those comments about minor nose imperfections causing 'minor' accuracy problems. Purposely induced in some guided projectiles to prevent 'dead zone' errors. About as important as the Coriolis effect to most of us.

[W.R.Buchanan]

Tim: great job of reigning in the Housewives of Beverley Hills, or was it,,, Atlanta?.

I love the discussions,,, but really dislike when that discussion turns into a snotty exchange of low grade insults. I mean really,,, were pretty much all men here, right,,, and if you're going to call someone an ***** then at least you could spell it right so everyone can understand exactly where you stand.

This particular subject is one that I think very few people fully understand. I know I don't, and for the simple reason that it is beyond the scope of my interests. This is because my individual accuracy requirements won't be significantly affected by it. (whatever it is ?)

If it were something that I needed to understand then I would explore the subject in depth and "Clear" all the technical terms so that I in fact,,, "did understand",,, all I knew about the subject in question.

I doubt anyone here has done that on this particular subject, so as a result all the insults become moot!

Just because you have read something doesn't mean you understand it, and this should be obvious to most intelligent individuals, and less obvious to the people I am talking about.

People here and in other forums as well do tend to Puff Up easily when they don't understand something that has been written or stated..

It has a lot to do with not being able to see the person you are talking to and reading his intent into the conversation. Simple example is When you can't see someone, you can't see if they are smiling when they call you an *****.

The unspoken part of the conversation is something we deal with everyday and yet it is missing when conversing on a forum. Smileys help but still are not a substitute for actually seeing the person you're talking to. :veryconfu

I will tell you all again and I have made this point numerous times since joining this forum several years ago.

the "Mis-Understood Word" is the "root" of ALL conflict. NOTE: I Said "ALL conflict" This is as close to an absolute fact, as can exist.

How many times? have I warned you to read and re-read a post until you fully understand what the person is trying to say, before going off on him, or cherry picking a phrase out of context and quoting it to make YOUR point? [smilie=b:

I consider it to be "Poor Form."

Good job Tim! Sorry to Hi-jack this thread ,,, but then again did I really hi jack it, or is my point what we were actually discussing in the first place? :mrgreen:

Randy,,,

[303Guy]

Well said, Randy. And to repeat -
Good job Tim!


epicyclic precession mode - Caused by aerodynamic forces,But the initial instability is caused by bullet yaw as it leaves the muzzle, right? The spiral path is caused by the primary yaw which turns about it's axis at a slightly lower rate than the spin due to gyroscopic forces which results in the aerodynamically induced spiral flight path.

[youngda9]

How? the only thing that changes is twist, not dimensions. Once the boolit engages the rifling, it is engaged isn't it?

Well...I've seen what a shot boolit looks like with linear grooves going the length of the boolit at a constant angle(determined by the twist rate). The boolit seals to all of the land/groove nooks and crannies if it is sized and obturates correctly. Now imagine if that twist angle is increasing in angle as the boolit is going down the barrel. Seems to me the trailing edge would disengage from the rifling as the angle of rifling increases. Gas would find its way through the gap. The boolit would try to continually obturate I would think, but no doubt there would be problems as the twist is increasing and pressure is decreasing near the end of the barrel travel.

My $0.02

[Artful]

So the typical yaw of a boolit is not really important to us. Evidently tail heavy or nose heavy doesn't matter either. I don't understand why we don't use power law ogives for better transonic performance. As for the video, understand it is still gyro action that causes the sudden, drastic change in direction.

http://www.longrangehunting.com/articles/bullet-pitch-yaw-1.php

[popper]

303guy - I don't know. Obviously the helical starts someplace and it's radii can get larger and smaller (boolits going to 'sleep') & maybe larger again. Once the boolit leaves the muzzle, it's all aerodynamics/gyro torque action. LG proposes it is due to imbalance. Letiz proposes partly by nose steer (forces on the nose cone - think angle of attack) and tests to validate that it's effect is small. Personally, I'm interested in the effect of tail/nose heavy design, relative to the moving center of force. It is actually a 'wash' as all I can control is my boolit consistency and bbl harmonics by tailoring the load.

[35 shooter]

Well said, Randy. And to repeat -

But the initial instability is caused by bullet yaw as it leaves the muzzle, right? The spiral path is caused by the primary yaw which turns about it's axis at a slightly lower rate than the spin due to gyroscopic forces which results in the aerodynamically induced spiral flight path.

Which leads me with what little i understand after reading all these different terms and forces on the boolit right back to rpms as being a major factor on how all this transpires after it leaves the bbl. To me it just makes sense there comes a point with a soft projectile(boolit) where it has been overspun in the bbl, and looses it's ability to come back near it's original shape as it exits or before or both. I'm quite sure it's a combination of all things being discussed plus how precision ones chamber, bedding, bbl., is also. And how precision ammo has been loaded, what powder burn rate etc. etc. It seems to me rpm versus bbl. twist and boolit weight has been the best guide so far to predict where trouble is going to start for me. Then go to a slower burning powder keeping rpm's about the same trying to maintain accurracy and go a bit faster has been working for me. Just saying rpms may not be the answer to all of it, but the predictions within the theory sure keep kicking me in the tale so far or at least it seems, that way. It's a royal pain is what it is.:) All this diversity of info on these forums sure keeps me going to the range a lot!

[geargnasher]

In gain twist, the leading edge of the front bearing surface encounters the steeper twist angle first, so the engraves at the front end would be wider by muzzle exit time same as the "skidding" a revolver boolit often sees. The tapered engrave, in and of itself, should have a negligible effect on exterior ballistics. However, I postulate that part of the accurate velocity limit of a given system has to do with boolit damage occurring near the forward portion of the barrel, after conventional wisdom indicates the boolit is "safe" from launch damage. No way to tell for certain without pre- and post-limit samples of undamaged, recovered boolits or boolits being fired under those conditions and captured via air-gap flash photography.

What happens outside the barrel seems fairly obvious to me.

Gear

ETA, Dick, your investment might be better directed toward high-speed photography rather than rifles. Once the WHAT is understood, it doesn't take a stable full of rifles representing the full range of common twist rates to prove it. It could be done with a factory .308 Winchester.

[Digital Dan]

Bullet skid in gain twist barrels in not an issue,nor is gas cutting. It would seem intuitive, but that assumes the land width is the same dimension at the muzzle as the breech. It is not always the case nor is it accidental. It also is common to think the rate of twist change is great, but this is not the case either.

[Love Life]

I'll put my investment into jacketed bullets and call it a day.

[Digital Dan]

epicyclic precession mode - Caused by aerodynamic forces, not imbalance or RPM effects. Also called nose steering. Remember all those comments about minor nose imperfections causing 'minor' accuracy problems. Purposely induced in some guided projectiles to prevent 'dead zone' errors. About as important as the Coriolis effect to most of us.

I respectfully suggest it is caused by both aerodynamic forces and imbalance. Epicycloid motion in gyroscopically stabilized projectiles is by definition the combination of two precession modes, in the case of bullets each mode has its own cause. Aerodynamic forces cause the slower precession mode.

http://en.wikipedia.org/wiki/Epicycloid

http://arxiv.org/ftp/arxiv/papers/1205/1205.2071.pdf

[303Guy]

That last one hits it on the nail (as far as explaining it goes).

[youngda9]

Looks to me like the change of twist rate would carve up a cast boolit. I can't seem to find a picture of a fired boolit. The image below illustrates what I'm talking about. The obturated boolit would be encountering ever changing rifling with the leading edge twist rate being changed, and the trailing edge constantly being abandoned by the rifling...with perhaps lead being attempted to be pushed back into the trailing edge by the lagging leading edge (per the twist) as the boolit travels down the barrel. I hope I explained that in an understandable manner.

92865

[W.R.Buchanan]

Good to see that we have regained civility.

Randy

[geargnasher]

I'll put my investment into jacketed bullets and call it a day.


That works, too. When I get frustrated and want more out of a rifle than I can figure out how to get, I jacket mine in paper. I'm just too cheap to buy bullets and too lazy to stay after copper fouling.

This graph makes me think a reverse gain twist might be the ticket for cast boolits: http://www.varmintal.com/6ppc-distance.png

Gear

[Love Life]

I'm just too cheap to buy bullets and too lazy to stay after copper fouling.

Funny you say that...

I rarely clean a rifle barrel. I will when accuracy takes a big drop, but not until then.

My 308 averaged 350-400 rds before I cleaned it.
My .243 hasn't been cleaned in 200 shots and it still shoots 1/2 MOA at 100 yds and something like 3.5 to 5 inches at 600 yds off bipods with no rear bag(witnesses and stuff).

Once accuracy pinches a loaf I hit it with a patch soaked with butches bore shine, go have a smoke, come back in and patch it dry, and go shooting some more.

I'm sure if I was shooting benchrest I would have to clean more, but for super cool ninjery long range shooting I find it unnecessary to clean the barrel after every range trip. It's just not needed. I wipe the action down, and add more grease after every shoot though.

[geargnasher]

That's 'cuz you gots a Kreiger.

Gear

[Love Life]

Naw. The 308 was fine as well. One day I'll clean my Remington 700 8X57 barrel.

I laugh when I watch someone meticulously clean a barrel, and then the 1st thing they do is fire fouling shots. Lame.

[popper]

http://arxiv.org/ftp/arxiv/papers/1205/1205.2071.pdf
The claim is that the nose points inward to the axis of the helix. It does NOT state that the PATH of the boolit is different (unless I missed that in the fine print). A second problem is the analyzed fps goes from M1 to M1.5, an area where ogive theory states our typical 'nose cone' performance is very poor (i.e. very unstable). @ 1000, the 168 SMK (308W) is barely stable, dynamically. Our CB ogives are much poorer. How the heck did that retired Doc hit the 1200' target with BP & I assume cast?
I buy into the RPM theory that bad boolits cause poor accuracy.

[Larry Gibson]

................I buy into the RPM theory that bad boolits cause poor accuracy.

That is the trick with cast bullets; start with balanced bullets and keep them balanced during acceleration in the barrel. Once they are in the air the laws of external ballistics and physics reign. Note all of the sites referenced refer to that simple ballistic fact; "bad bullets" (bad as imbalanced) are inaccurate and the higher the RPM the greater the inaccuracy.

Also note all reference are discussing jacketed bullets and most often match jacketed bullets at that. Those start out as the most balanced of bullets to begin with. Jacketed bullets and do not sustain near the damage (as in imbalance) that cast bullets do during acceleration. The references listed thus far mostly discuss initial bullet stability and why some of those bullets "go to sleep" and what causes that phenolmena. All that is well and fine but none of the references listed have discussed the phenomena of; why at a certain point do cast bullets lose accuracy dramatically? Other references do discuss that and give the reasons why such as Rinker's work (referenced by one of the authors listed in this thread).

We most often see, in our own shooting and testing, examples very often of cast bullets not "going to sleep" where accuracy gets worse in the non-linear sense as the range increases. The posted groups of the test here is and example as is the posted groups on the oversize 6.5 CM thread. Those show how accuracy decreases as the velocity increases and how, as the velocity increases, the accuracy at a farther range is very much worse in the non-linear sense. That demonstrated phenomena is at complete odds with the discussions of "best" bullet stability and the phenomena that bullets 'go to sleep" and shoot smaller groups as the range increases. So what is with that? Why the difference?

The references, if cast bullets are used, beg the questions;

If what the references discuss here is the case with cast bullets then why were the groups at 200 yards in those tests not smaller?

Do all bullets "go to sleep" and shoot smaller groups at longer range, especially cast bullets?

How many of us actually shoot consistently smaller groups of a sufficient sample size of cast bullets at longer range?

Are not most of our groups shot at longer range with cast bullets in fact larger?

Just food for thought.

Larry Gibson

[popper]

In an attempt to give some reasoning to your food-for-thought questions, there are 2 (probably more) opposing laws of physics. One is the natural stabilizing of a spinning projectile. The other is the opposing destabilizing effect of unbalanced boolits. When the 2 'cross' you get an increasing accuracy 'cone' or the tangential boolit trajectory. Where do they 'cross'? Who knows. As for 'gain' rifling, my understanding is that the twist starts out slow and increased when less pressure is needed to rotate the bullet. The angle of the rifling increases. The opposite makes no sense.

[Larry Gibson]

The opposite makes no sense.

Absolutely correct.

However if we note in almost all instances (the oversize 6.5 CM bullet aside as it apparently has other issues) our cast bullet holes at longer ranges in loads where accuracy is lost exhibit no sign of bullet destabilization. All go through the target making nice round holes.

Also if we compare the accuracy of milsurp bullets (same cartridge, same rifle, same velocity) to match bullets we always find the match bullets to be more accurate at all ranges. We know the milsurp bullets are not of the quality (in this case "quality" refers to consistency of manufacture, i.e. potential balance) of match bullets which are very consistent and balanced. Both make nice round holes in the targets at all reasonable ranges including what we consider "long range". No signs of instability exhibited by the poorer in consistency of balance milsurp bullets.

So why are the match bullets then more accurate if stability is not the issue?

Larry Gibson

[geargnasher]

That is the trick with cast bullets; start with balanced bullets and keep them balanced during acceleration in the barrel. Once they are in the air the laws of external ballistics and physics reign. Note all of the sites referenced refer to that simple ballistic fact; "bad bullets" (bad as imbalanced) are inaccurate and the higher the RPM the greater the inaccuracy. This is true.

Also note all reference are discussing jacketed bullets and most often match jacketed bullets at that. Those start out as the most balanced of bullets to begin with. Jacketed bullets and do not sustain near the damage (as in imbalance) that cast bullets do during acceleration.... With "standard" loading practices for cast boolits as outlined in most loading manuals, this is largely true. But I think it is incorrect to make the automatic assumption that cast boolits necessarily sustain damage during acceleration because such damage can be avoided by a skillful handloader and then, like you said, no imbalance, no ill effects.


Pardon my selective 'snips' Larry, but I wanted to comment on specifically those two points.

Gear

[Larry Gibson]

Gear

Your comments are essentially correct. However, to make the assumption that a cast bullet is not damaged or unbalanced to any degree is, while the worthy endeavor we all strive for, not accomplished very often and then not consistently. It is one of the major reasons we shoot groups instead of all the bullets going into the same hole. Such is eloquently stated in the posted references.

I think all of us would admit at some point we all damage cast bullets during acceleration, especially when working up loads? Who among us shoots perfect cast bullets? We may shoot what are really excellent cast bullets but are they as perfect as jacketed match bullets? Additionally, as your previous comments here attest, the bullets are damaged (unbalanced) by the rifling when they are engraved. We understand that because we know such is mitigated by breach seating bullets. So the question remains; if there is an imbalance and it does not affect the stabilization of the cast bullet then what is the reason for increasing inaccuracy as range increases? Another question might be; what does the degree of imbalance and at what is the bullet in flight influenced by it to the degree of inaccuracy occuring?

Larry Gibson

[303Guy]

I've experienced boolits shooting quite fine at about 40 yds but lousy at 190 yds. I only managed to capture all the shots because I had a very large cardboard target. All the holes were very round and they were long boolits. Maybe by that distance the boolit yaw had dampened out. The dispersion was random - not in a ring which would be cone evidence.

[Larry Gibson]

If we read all the references posted we might assume that all bullets fired, jacketed and cast, exhibit enough yaw that they shoot smaller groups at longer ranges than at shorter ranges; i.e. larger groups at 100 yards than at 200 yards. But is that really the case? Do we always shoot smaller groups at longer ranges because the bullets “go to sleep”?

The truth is bullets “going to sleep” to shoot smaller groups at longer ranges is a rare phenomena. On another forum joeb33050 analyzed the last 10+ years of record CBA scores. He found that the 200 yard groups were almost exactly twice the size of the 100 yard groups after wind conditions were factored out. That is linear group dispersion. None of the record scores at 200 yards were smaller than the same score that rifle/ammo/shooter shot at 100 yards. How many of us have actually shot a smaller group of equal and sufficient sample size (for a reasonable measure of assurance) at say 200 yards than was shot at 100 yards with the same rifle/load on the same day under the same conditions? I haven’t.

But I have shot smaller 3 and 5 shot groups at longer range but those give little assurance. I once shot a .5” five shot group at 300 yards with my match M1A with match iron sights. However, the following 15 shots spread the group to a little over 4” which was the real accuracy capability of that rifle with that load with me shooting it. That load would shoot in 1 - 1.25" at 100 yards with that particular load. The 1st 5 shots of that 20 shot string just happened to go into a smaller group at 300 yards due to random dispersion. The following 15 shots demonstrated that being a sufficient sample size.

Just today I shot groups at 100, 200 and 300 yards with the 311466 at 2600 fps. The rifle is capable of 1.5 – 2 moa and 100 yards consistently of 10 shot groups with that load. Thus if all was well the groups at those three ranges should show a linear dispersion of 3 – 4” group at 200 yards and a 4.5 – 6” group at 300 yards. I had 26 rounds so I shot 7 at 100 yards to confirm the 100 yard zero. The 7 shots is the minimal statistical sample size to give a meaningful assurance. I then added 3 moa elevation to the T-16 scope and shot 9 shots there. At 300 yards I added another 4 moa elevation and shot 10 shots there. The day was very nice at 63 degrees, sunny with a 0-3 mph wind out of 7 – 9 o’clock. I made no correction for wind but shot straight away with the bottom of the 1” diamonds being the POA.

The 7 shot 100 yard group was 1.455”. The 9 shot 200 yard group is 3.7”. The 300 yard group is 5.25”. All fall easily in the expected range of linear expansion as the range increase. No sign of the bullets “going to sleep” and shooting smaller groups at longer range. All the holes are nice and round with no sign of any, or at least any excessive, yaw. That rifle does that consistently day in, day out, on demand with that load.

So that brings us to your example 303Guy. Obviously the bullets you fired did not “go to sleep” and produce a smaller group than the “fine” group you shot at 40 yards. Obviously the group dispersion was very non-linear. So what do we suppose was the cause of the 190 yard group?

Larry Gibson

9294392944

[geargnasher]

Properly stabilized bullets and launched boolits/bullets recover from launch yaw within 20-40 yards. If you want a real eye-opener, shoot your .308 at a really small aim point with a good load once each at ten feet, 20 yards, and 40 yards.

If dispersion of a 1-moa load is linear from the muzzle, you should be able to shoot a .425" ragged hole at about 12 yards with a .308. Try keeping the group under a half inch. Might be harder than you think if the yaw is bad enough.

Gear

[singleshot]

I personally don't see much to be gained from shooting cast in a gain-twist barrel (see what I did there?), but that's why we test things. I've finally recovered from the J-word statement up above (no offense Love Life) and will continue to PP mine when I get a wild hair to push my Rusky mil-surp MN's with <10" twist to 2600 fps plus. The more I think of it, the more I think a PP would stand up to gain-twist rifling better anyway.

As an aside, keep up the good work goodsteel, you have an iron constitution! Info and discussion are great, but the rest is grating. (See, I did it again!)

[Larry Gibson]

Gear

Can you explain how .425 at 12 yards is moa? According to my math that is 3.541" at 100 yards if linear and slightly under 3.5 moa?

I have done initial 25m zero with M14s, M21s and M24s with a variety of sights (iron, scopes and night vision). Groups under .5" were common with M118, M118SB, M852 and M118LR. Not sure I understand your "test" or it's relevance. Willing to do it but do not see your point nor what it will prove relevant to 303Guy's 40 and 190 yard groups? If 303Guys bullets went to sleep by the 40 yard group then why what happened at 190 yards? That was the question....answer?

Larry Gibson

[singleshot]

Just today I shot groups at 100, 200 and 300 yards with the 311466 at 2600 fps. The rifle is capable of 1.5 – 2 moa and 100 yards consistently of 10 shot groups with that load. Thus if all was well the groups at those three ranges should show a linear dispersion of 3 – 4” group at 200 yards and a 4.5 – 6” group at 300 yards. I had 26 rounds so I shot 7 at 100 yards to confirm the 100 yard zero. The 7 shots is the minimal statistical sample size to give a meaningful assurance. I then added 3 moa elevation to the T-16 scope and shot 9 shots there. At 300 yards I added another 4 moa elevation and shot 10 shots there. The day was very nice at 63 degrees, sunny with a 0-3 mph wind out of 7 – 9 o’clock. I made no correction for wind but shot straight away with the bottom of the 1” diamonds being the POA.

The 7 shot 100 yard group was 1.455”. The 9 shot 200 yard group is 3.7”. The 300 yard group is 5.25”.
Larry Gibson

9294392944

Larry, I'm curious of the rifle and cartridge that shot thusly. Mind sharing?

[geargnasher]

I said .425" RAGGED HOLE. Does that not imply an outside-to-outside-measured group?

.310" (sum of two radii) + .125" (CTC predicted linear dispersion @ 1 MOA @ 12 yards) = .425".

The relevance is that yaw stabilization, if yaw is occurring, happens much closer to the muzzle than many people realize, but CAN be stretched out or delayed for reasons I don't fully comprehend, but can test and observe. Spin-stabilization does a lot of work to bring a yawed and spiraling projectile nearer the centerline of departure, perhaps more than it is given credit for. If 303Guy's groups opened up past 40 yards, particularly if they were in a non-linear fashion, then the projectile has become unstable probably due to balance or SG/CP issues or launch damage. Many of his boolits (not sure about the ones in question here) are radius-nosed cylinders, cast from very soft lead/tin alloy, some with rebated bases and may be borderline-stable to begin with, so we might expect a degree of non-linear dispersion (no offense or criticism, 303Guy, I'm simply pointing out some possible explanations).

I have observed elliptical impacts from cast boolits at 12 yards and disproportionately large groups at close range regularly, but not always. A confirmation is to move the target away three inches per shot for ten shots. I have shot groups that were 3/4" edge-to-edge at 12-13 yards and still barely over an inch ETE at 100. Yawed impacts walked like a clock hand on the close target. I have no other explanation but that the boolits went to sleep by 30-40 yards, as the smallest groups (actual measurements) from some loads occur for me between 20 and 50 yards. I've read postings on benchrest sites indicating that "harmonics" puts the boolit in a more stable part of the cycle at different ranges (100, 200, 300) and must be tuned, and also have read that it is more shooter aptitude than anything, so experiences and opinions vary greatly even among the hair-splitters of our sport/hobby.

Am I alone in my findings?

Gear

[Larry Gibson]

Gear

Thank you for the explanation. Wasn't sure what you meant.

What specific rifle, cartridge and scope did you use to " I have shot groups that were 3/4" edge-to-edge at 12-13 yards and still barely over an inch ETE at 100."?

It is well known that many bullets have yaw or wobble when first launched and the settle down quickly. The term "go to sleep" and usage for such is most often relegated to short ranges of 100 yards and longer ranges of 200 yards plus. Can you enlighten us on what the initial yaw smoothing out before 40 yards has to do with non-linear group dispersion at longer ranges past 100 yards?

If 303GUYs projectiles became unstable, perhaps as you suggest, then how was it; "All the holes were very round and they were long boolits." to quote 303Guy? Would not those holes at 190 yards exhibit yaw or key hole as did your close range bullet holes mentioned, the CM bullet holes you've mentioned in another thread and the same indication of yaw and key holing and probable instability in the CM bullets I recently tested? If 303GUYs bullets were, in fact stable as evidenced by the "very round" bullet holes, then perhaps something else was at play, perhaps?

Larry Gibson

[Larry Gibson]

Larry, I'm curious of the rifle and cartridge that shot thusly. Mind sharing?

That is a wartime Nazi M98 Mauser action firmly pillar bedded into a fiberglass copy of the old Savage 112V stock. It has a 27.5" Schultz & Larson Palma barrel chambered in .308W that came off a Huskvarna Palma rifle. The original owner put one box of Sierra 155 Palma MKs through it and then decided he wanted a 6.5 caliber Palma Rifle so he had the barrel pulled and the Husky rebarreled. The gunsmith gave me the barrel as the owner didn't want it. Scope is an older original Weaver T-16 in Redfield one piece base and rings. The barrel screwed right into the M98 action (the rifle used to be my own 6.5-308 match rifle) and was about .015 short of headspacing. I reamed the chamber with a match finish reamer to minimum headspace spec. Probably would shoot better if the action was "trued" and all that stuff but other than the match chamber and the solid pillar bedding there's nothing special about it.

Load has been mentioned before but it is the 311466 sized .311 with Hornady GCs over 49 gr AA4350 in LC92 cases with a WLR primer. Nothing really special there either, just picked a properly designed bullet and slow burning powder for HV cast bullet shooting.

If there is anything "special" it is the 14" twist.

The 300 yard group would have been closer to 4.5" had I adjusted for the wind. As you can see from the group that slight wind coming out of 7 - 9 o'clock was taking a toll at 300 yards.

Larry Gibson

[geargnasher]

I am saying this: Boolits can yaw at muzzle exit, enough to make close-range elliptical holes, then stabilize to shoot small groups with round holes in less than 40 yards. This is due to launch-induced yaw, NOT imbalance per se. Now, switch gears. Suppose the group either gets larger in a linear, or sub-linear, or super-linear fashion past the yaw-stability point depending on how well the boolit is balanced, how fast it's spinning, barrel harmonics (this last with regard to sub-linear dispersion according to the BR crowd, not my own experience as I can't speak with authority on that), and I'm sure plenty of other, subjective factors. Whether boolits that group smaller proportionally at 200 yards than 100 experience a yaw/recovery cycle of any consequence in the first few yards would be interesting to discover. Boolit Gymnastics is what I'd call it. I tend to think such sub-linear trends at 200 and 100 are more likely to be instances of delayed yaw stabilization.

Gear

[303Guy]

Well, just to clarify, the 40 yd 'group' was a little informal - fired into a clay bank and assessing the hole size. The 190 yd (measured) 'group' was from the batch with the smallest hole in which looked like all the shots had almost landed on top of each other (of course they hadn't). So, not very scientific. And it may have been closer than I remember. Even so, the very round holes surprised me considering the 'group' size (and I use the word 'group' loosely here). These were paper patch trials so it is likely that the patches were causing the problem. But no discernible yaw?

[Larry Gibson]

303Guy

Any idea of the velocity?

Larry Gibson

[geargnasher]

Gear

Thank you for the explanation. Wasn't sure what you meant.

What specific rifle, cartridge and scope did you use to " I have shot groups that were 3/4" edge-to-edge at 12-13 yards and still barely over an inch ETE at 100."? Sorry I'm a bit fuzzy, I'm super-tired. Let me try again by posting within your post. I skimmed my loading notes and I've seen this during various tests with two .30-30 carbines and two different boolits (311041 and much more pronounced with the RD 170 with the real grease grooves), my M-70 featherweight .270 with the RCBS 150, and a M-70 classic sporter .30-06 using the AM 31-185G and 311041, but oddly never with the Lee 31-185 rn. I NEVER observed, but did test for this short-range yaw with my scoped Swede M96 using the shortened CM and both Lyman boolits. If they yawed, it was forever, though sometimes it did or didn't ever get any worse. All rifles wore various brand 3x9 optics set to 9, I rarely ever adjust the magnification. The other .30-30 had open sights and I can't see finely enough to shoot under 2" at 100 with my eyes so it really doesn't tell much. The others, at most shot 1-1/4" or far less (some at half-inch for ten, lazy speeds, the '06 at repeatable 3/8" ctc for five) with the loads I tested.

It is well known that many bullets have yaw or wobble when first launched and the settle down quickly. The term "go to sleep" and usage for such is most often relegated to short ranges of 100 yards and longer ranges of 200 yards plus. Right, that's what I was assuming here. Can you enlighten us on what the initial yaw smoothing out before 40 yards has to do with non-linear group dispersion at longer ranges past 100 yards? Nothing unless groups appear to get big at (say)100 and then group a smaller MOA reading at (say) 200. I'm thinking that COULD be what I've been calling delayed yaw stabilization, no? Where the initial yaw doesn't calm down at the normal short range, but takes much longer, yet DOES eventually quiet down? I really only mentioned this because it would be simple enough to test. If a rifle system shoots like your Mauser above, it would be interesting to find out what it's doing in the first few yards.

If 303GUYs projectiles became unstable, perhaps as you suggest, then how was it; "All the holes were very round and they were long boolits." to quote 303Guy? I'm saying he was experiencing non-linear group dispersion, AFTER the yaw calmed down and the boolits were pointed more straight, yet not following a straight-line path to the target (corkscrewing but no longer yawed). Would not those holes at 190 yards exhibit yaw or key hole as did your close range bullet holes mentioned No, they wouldn't necessarily still be yawed. I'm talking about two different phases of boolit stability here: close range yaw/stability and long-range balance/imbalance dispersion., the CM bullet holes you've mentioned in another thread and the same indication of yaw and key holing and probable instability in the CM bullets I recently tested? Like I put in your previous paragraph, if the CM yawed it was eternal, from the muzzle to infinity (and beyond!) If 303GUYs bullets were, in fact stable as evidenced by the "very round" bullet holes, then perhaps something else was at play, perhaps? Ya, perhaps :wink:, but I really my concentration these last few posts has been on what causes "going to sleep" rather than what causes groups to blow up at ever-increasing range. We both know full-well what causes that.

Larry Gibson

Oh, one more thing, the "delayed yaw stabilization" that I'm postulating can cause some instances of smaller MOA's further downrange may or may not cause noticeably elongated holes on the downrange targets, or they might all be oriented the same direction. I DO know that as the yaw and group size decreases as stabilization occurs at short range, the holes become round. Same could happen if the yaw stabilization was delayed for 200 yards, no? Maybe not, just throwing it out there.

Gear

[geargnasher]

Here's a neat one, shows what happens when you are pushing boolits way past the comfy velocity zone and screw up the QC on two of them somehow. I think I had some sprue nibs on some of these from a loose plate and I didn't cull them well enough. The whole batch would do this tight/yawed flyer thing, lube not withstanding, which is what I was testing at the time. Anyway, if all five had been as badly balanced as the two flyers, you can see what the group would have done. BUT, three of them were done right and held true even going well past the "RPM Threshold". Most of the time my groups either totally suck or pack in tight depending on how well I walk the tightrope at high velocity, this one was split.

http://castboolits.gunloads.com/attachment.php?attachmentid=62346&d=1361757719

I have some Duesie pics of what the 266469 will do out of a .270, paper patched, due to the under-bore core, but they are saved on another computer and lost from here in the image-hosting fiasco from a couple years ago. Horizontal strings of identically-oriented elliptical holes; looked like I had thrown little frisbees through the target. Might still have the target but I didn't notice it in the .270 binder earlier.

Gear

[Larry Gibson]

"It is well known that many bullets have yaw or wobble when first launched and the settle down quickly. The term "go to sleep" and usage for such is most often relegated to short ranges of 100 yards and longer ranges of 200 yards plus. Right, that's what I was assuming here. Can you enlighten us on what the initial yaw smoothing out before 40 yards has to do with non-linear group dispersion at longer ranges past 100 yards? Nothing unless groups appear to get big at (say)100 and then group a smaller MOA reading at (say) 200. I'm thinking that COULD be what I've been calling delayed yaw stabilization, no? Where the initial yaw doesn't calm down at the normal short range, but takes much longer, yet DOES eventually quiet down? I really only mentioned this because it would be simple enough to test. If a rifle system shoots like your Mauser above, it would be interesting to find out what it's doing in the first few yards."

That would be correct and is what essentially is occurring when most everyone discusses bullets “going to sleep”. Few consider the close range, as in less than 40 yards, aspect at all. I don’t think anyone is disagreeing that it is happening at all (is anyone?). My point was, not that it wasn’t happening, but that it’s occurrence of shooting larger groups at say 100 yards than at 200 yards is a rare phenomena. Thus the phenomena is not observed because as you say the bullets almost always have “gone to sleep” before 40 yards. Any groups shot past that range will then open in a linear or non-linear fashion as the range increases.

It would be difficult to do your test with that rifle as the scope will not focus down to 12 yards and parallax also becomes an issue. I'm sure you know that is also the case with many scopes unless specifically made to focus at that short of a range. As we know most "big game" scopes w/o parallax adjustment (either on the front objective lens or a side mount adjustment) are set parallax free at one specific range, usually 100+ yards. Parallax then with ne either positive or negative on either side of that range. Suffice to say though if that rifle had yaw it was well smoothed out long before 100 yards and did not occur again through out the 300 yard flight of those bullets.

"If 303GUYs projectiles became unstable, perhaps as you suggest, then how was it; "All the holes were very round and they were long boolits." to quote 303Guy? I'm saying he was experiencing non-linear group dispersion, AFTER the yaw calmed down and the boolits were pointed more straight, yet not following a straight-line path to the target (corkscrewing but no longer yawed)."

So what do we suppose was the cause of that “(corkscrewing but no longer yawed)” in those obviously still stable bullets in flight?

You mention “long-range balance/imbalance dispersion”. What then is a ballistic reason during such a bullets flight that causes it to “disperse” as such in a non-linear fashion as the range increases?

Reference you last post with the target photo; “I think I had some sprue nibs on some of these from a loose plate and I didn't cull them well enough. The whole batch would do this tight/yawed flyer thing, lube not withstanding, which is what I was testing at the time. Anyway, if all five had been as badly balanced as the two flyers, you can see what the group would have done. BUT, three of them were done right and held true even going well past the "RPM Threshold".

What do we suppose it was that caused those 2 bullets with the “sprue nibs” and the “flyers” in the “whole batch” which you say were “badly balanced” to fly out of the group “past the RPM Threshold”?

Is it possible that some bullets in such a load as yours might have remained balanced enough that they have not gone past their own individual RPM threshold?

Is it possible, in your example target, that only the bullets that were “badly balanced” had gone “well past the RPM threshold” and are the flyers we see.

Is it possible that an assumption that the RPM threshold as a set RPM (appears to be your meaning?) and any bullet over that set RPM (call it a limit) is going to be a flyer and not "group" is incorrect?

Is it possible, if that assumption the RPM threshold as a “set limit” is incorrect, that only the “badly balanced” flyers were “well past the RPM threshold” and thus the "flyers" ?

If we read other ballistic references that discuss RPM, since you brought the subject up, and its necessity for bullet stabilization don’t they also discuss a force created by the RPM that may have an adverse affect on a bullets ability for its center of gravity to spin around it’s center of form?

Do those references also allude to such a forces adverse affect on accuracy?

If you have read those references on ballistics then what may that force created by RPM be?

Larry Gibson

[MBTcustom]

Good discussion.

If I may put in my 2 cents worth. Please take it for what its worth. I am not trying to discourage anyone's personal belief about what happens to a boolit in flight, and I'm not asserting my view on this as gospel.

I have mentioned in open forum that I disagree with the RPM theory. I do not argue that it exists at all. In fact, I have observed it in laboratory environment spinning things at high RPM and observing the effect. I only disagree that it always applies within the confines of the speeds we are shooting.
This is what I have seen.
If I make an aluminum cup about 1.5" in diameter, with a cavity about 1" deep with about a 1/8" wall, put it on a high speed motor shaft and spin it up to 10,000 RPM, it will begin to ring at a certain point like a bell, or more like Benjamin Franklin's glass harmonica. It's actually quite deafening. I noticed that this ringing occurred at a very specific rpm. Basically, I made an apparatus that would allow me to audibly hear the rpm threshold being crossed by this cup.
I took more care with the alignment of the cup to the shaft, and observed that I "pushed the rpm threshold up" just as Larry Gibson says.
I kept doing this, and getting the cup more and more perfectly balanced, but what I noticed is that the RPM threshold goes up exponentially to the perfection of the cups alignment to the shaft.
When I finally got the cup nearly perfect in every way, I had it running about .0001 TIR, and we were able to push the RPM up past the 20,000rpm "wall" we were stuck at, up to nearly 40,000 RPM with not a hint of ringing at all.
It was obvious to all observing, that when it comes to spinning things at high RPM and keeping them stable, accuracy and alignment pays huge dividends towards pushing up the RPM threshold, to the point that I postulate it would cease to be an issue for a cast lead boolit or any projectile.

Furthermore, the bell didn't just start ringing all of a sudden. It got louder and louder as we approached the RPM threshold (while it was still running imbalanced), and pushing past it would give an effect where it was no longer ringing per se, but the vibration it put off was impressive etc etc etc.
The point is, the boolit is not either "balanced" or "imbalanced" but there were certain "nodes" of RPM where it liked to exist, and this was observed even when the threshold had been crossed.

My personal belief is that we are able to get a perfectly balanced cast boolit into the barrel, and past the crown, and while the boolit may be damaged, it is damaged in a concentric manner.
This is why I take such pains to align a rifles chamber to the bore, and ream it perfectly straight, and why I have left a bit of flare on the mouth of the case (hey it seemed to work sometimes!) to align the boolit between the case flare and the bore rider.

I think that a given alloy has only so much ability to right itself when thrown imperfectly into a rifled barrel. Copper is able to do this, and PP is able to cushion this, and a sabot just doesn't give a dam.
A naked cast boolit is too week to right itself and it gets damaged upon entry into the barrel, and (if that barrel has hook), upon traverse chamber to crown.
I think that if you can get your system of rifle, brass, barrel, and chamber to be perfectly aligned while under the pressure of firing! it is possible to shoot much faster than a typical rifle is capable of.

Where's you proof?!?!?!? (you might say whilst slapping the table so hard the silverware rattles.)
I don't have any....yet.
I have a bunch of theories posted by the good people (some a little on the prickly side) of this forum, evidence that I have observed with my own two eyes (unrelated? irrelevant?), my wits, and my own theories about these things.

I will have answers someday. If I can get my business up and running, I intend to invest in some testing equipment that is astronomically expensive, and write about my findings.
Now, anybody who disagrees with my opinion and theory is free to do so. I'm hoping that we can all work together so that the truth can be found out, because I have a very strong suspicion that the truth lies somewhere between the lines that have been drawn in the sand.
Many have told me that I'm a fool for getting wrapped around the axle with this issue, but I was already going this way anyway. I could get there a lot faster if each of you people whom I respect (and some whom I love like brothers) would understand that you have no better grasp on the truth than I do, even though many of you have done much more shooting and experimenting than I have.

I believe that it all boils down to the boolits and the pipe. It has been my life's mission for the past three years to make those two things right, instead of dealing with their wrongness, and getting "close enough".
I am satisfied that I can chamber a barrel straighter than anyone else with my eye on cast boolit shooting which is an unforgiving mistress.
Now I am turning my sights towards casting the perfect boolit.

My father is a scientist. His words ring in my ears: change one thing. Turn the crank. Repeat.

[Larry Gibson]

goodsteel

Excellent post. I can see nothing in it to disagree with and actually agree with everything you said. As I also have often stated; getting the perfectly balanced bullet out the end of the barrel is the trick. Your suppositions, to which I do not disagree, are full of "ifs". The RPM threshold is not about when we keep the bullets balanced and "if" they are launched that way. The RPM threshold is all about what happens in flight when the bullets are not balanced and a certain level of RPM is reached. Unfortunately for most all of us when we push to higher velocity and RPM we do damage the bullet during acceleration and inaccuracy occurs. Thus the "perfectly balanced" cast bullet is not launched. The RPM threshold is about when that happens and how the bullet is affected in flight.

Geargnasher's posted target is a perfect example. Even considering the 5 shot group is not a sufficient sample size as the 3 shot cluster may indeed be just from random dispersion as evidenced by gear's admission of "The whole batch would do this tight/yawed flyer thing. Even so lets assume those 3 shots were well balanced and launched correctly. We thus have very good accuracy. Then the admitted probably unbalanced bullets are flyers out of the group. The unbalance was from a cast defect (gear said so) so lets assume all were equally accelerated and launched the same. If so then what was it that made the 2 unbalanced bullets flyers? Since the casting defects ("sprue nibs") are covered by the GCs other than unbalancing the bullets what affect on accuracy would they have had? Looking at the 5 bullet holes, which are very much identical, we can see no evidence of yaw. If it was induced in muzzle exit they have gone to sleep and should be following the same flight path as the 3 shots clustered if the "go to sleep" and get better accuracy theory is correct. Yet those 2 flyers are not grouping closer. They are opening up the group and I'd bet a 200 yard test of that ammo would have shown non-linear group dispersion from that 100 yard group.

So the question is; what was it that made those 2 shots with the unbalanced bullets fly out of the group?

I think we are all in agreement; launch the perfectly balanced cast bullet so the center of gravity and center of form are rotating around the center of spin and the accuracy will be excellent regardless of the velocity or RPM.

Obviously I did not do that with that 2600 fps 311466 cast bullet did I? However, it doesn't shoot too bad does it? So I must have come close, eh?

Larry Gibson

[geargnasher]

Larry, you're fishing to a point that I will address directly:

1). Every system has a limit.

2). Spin-stabilized boolits will not fly straight, as the target above indicates and you have posted numerous examples, if the degree of imbalance and/or launch yaw exceeds the capability of the spin-balancing forces to maintain a "true" flight path.

3). The flyers in the target posted above exceeded the stability limit and flew off-course, either from direct line of departure due to excessive launch yaw or from spiraling due to a radial balance issue, I don't know which. Perhaps the use of the term "balance" in the post with the picture wasn't an accurate description of what happened to that group, it may have been more "yaw" but there aren't enough data points to tell.
4). Every boolit has an RPM threshold unless it is 100% perfect. Every boolit has a yaw limit (based on diameter/mass/RPM/velocity) past which it cannot recover in the normal, short-range period. In the target above three were within the yaw/rpm limits, two were not. The RPM was ~154,400, pushing up the threshold normally encountered using "standard" loading practices. This is NOT an example of stellar loading practices by me, nor was I attempting to prove what is possible by that pic, only what happens when you DON'T to things right.

5). The RPM threshold of a boolit can be very, very high, well over 200K rpm if one does things correctly. Higher RPM ensures adequate yaw recovery at close range and adequate stability at extremely long range, and proper balance/launch ensures a true boolit that is unaffected by high RPM forces and will group very well, very far, with linear dispersion or possibly even sub-linear dispersion. THIS is the point of our disagreement because you haven't proved this last part to yourself yet. I will not do it for you, or meet with you to show you how. Sorry, but that is up to you. I will post from time to time any pertinent info, details of "how-to" etc. when I have some projects/accomplishments of interest.

SO, in conclusion and to restate what I've already said here before, I agree that there is an RPM Threshold or an "accurate velocity limit" as I call it, but it only applies to the degree of imbalance your boolits experience in flight. Fix that and the "threshold" is so far away you don't even need to look for it anymore. It WILL, however, bite you on the butt and remind you quite quickly when you get comfortable and sloppy with your techniques at high velocity.
Gear

[MBTcustom]

I basically agree with Ian. The high speed bell experiment that I did does also.
Ian's photo also shows what happens when a defect is fed to the RPM monster. If such a small thing can make such a big difference, then think how many ways the average caster could be messing up his groups and lowering the RPM threshold to the point that it matters. Just one defect could put you in that window. No?
So the question becomes "can the a average caster really get good boolits out of his mold, much less his barrel?"
Considering the responses I got on my thread on casting consistency, I would say "only if he cares to pay attention to detail".
No?

It also occurs to me that no booliteer would see the effects that Mr. Litz is describing unless he pushed the RPM threshold up to a point that it was no longer of any consequence, and then these subtleties could be observed more clearly.

[Digital Dan]

I think we are all in agreement; launch the perfectly balanced cast bullet so the center of gravity and center of form are rotating around the center of spin and the accuracy will be excellent regardless of the velocity or RPM.

Yep. And that discussion could have permutations one might never imagine.

Spin stabilization is a good thing, but it has baggage. Sometimes part of the baggage is making sure that all parties to the debate are on the same page conceptually. Seems simple but it doesn't always happen. I'm not commenting on recent posts on this thread (I think) but it has happened here and there. I recall earlier some dialog about the epicyclic swerve thing. The "swerve" and "precession mode" are different things. They are related, but somewhat haughty, cranky and unforgiving. They are difficult to precisely replicate from one shot to the next as well. Kind of like the random nature of dispersion cones and improbability theory.

I've waited for decades for someone to definitively prove that "sleeping bullets" can group tighter at longer range than short. Ain't happened yet so far as I know.

[Digital Dan]

So the question becomes "can the a average caster really get good boolits out of his mold, much less his barrel?"
Considering the responses I got on my thread on casting consistency, I would say "only if he cares to pay attention to detail".
No?

I would agree. Then there are a few of us using hammer dies to turn casts into very high quality swaged bullets that perform splendidly within the constraints of barrel/shooter/load quality. Nothing is perfect to be sure, but we do come fairly close on occasion. I've seen enough shooters defy my expectations too many times to think it an accident. That would include at least one member here who sometimes calls himself "The Lunger".

[Larry Gibson]

Geargnasher

"Spin-stabilized boolits will not fly straight, as the target above indicates and you have posted numerous examples, if the degree of imbalance and/or launch yaw exceeds the capability of the spin-balancing forces to maintain a "true" flight path."

"The flyers in the target posted above exceeded the stability limit and flew off-course, either from direct line of departure due to excessive launch yaw or from spiraling due to a radial balance issue,"

"Every boolit has an RPM threshold unless it is 100% perfect. Every boolit has a yaw limit (based on diameter/mass/RPM/velocity) past which it cannot recover in the normal, short-range period. In the target above three were within the yaw/rpm limits, two were not. The RPM was ~154,400, pushing up the threshold normally encountered using "standard" loading practices. This is NOT an example of stellar loading practices by me, nor was I attempting to prove what is possible by that pic, only what happens when you DON'T to things right."

The RPM threshold of a boolit can be very, very high, well over 200K rpm if one does things correctly. Higher RPM ensures adequate yaw recovery at close range and adequate stability at extremely long range, and proper balance/launch ensures a true boolit that is unaffected by high RPM forces and will group very well, very far, with linear dispersion"

"I agree that there is an RPM Threshold or an "accurate velocity limit" as I call it, but it only applies to the degree of imbalance your boolits experience in flight. Fix that and the "threshold" is so far away you don't even need to look for it anymore. It WILL, however, bite you on the butt and remind you quite quickly when you get comfortable and sloppy with your techniques at high velocity."

So then we are very much in agreement; there is indeed an RPM Threshold and you have in essence described it. Yes exceeding the RPM Threshold will bite you when you get sloppy. The more you exceed it the more it "bites"; i.e. flyers and larger non-linear group dispersion. We all, especially those who push to higher velocity, strive to launch the “perfectly balanced bullet” as goodsteel describes and alludes to. The problem is we don’t, or at least not very often and w/o great attention to detail an loading technique, which is why we still shoot groups no matter how perfectly we cast and launch cast bullets.

However, regarding; “THIS is the point of our disagreement because you haven't proved this last part to yourself yet”. You are incorrect about that. I have proved it openly on this thread numerous times; with Bass and the 311291 in the ’06, with the GB Kurtz bullet and the 266455 in the 6.5 Swede HV tests and recently with the .223 in the 9” twist AR. All pushed the RPM upward of 200,000 +/- and exhibited linear group expansion at longer range. All of those are examples of pushing the RPM threshold up. So even in that we are not in “disagreement”. But in fact, apparently contrary to your continued opinion, we are in complete agreement. Additional I have shown numerous times over the years on this forum what the benefits are by controlling the RPM via a slower twist with the .223 and .308W cartridges. In this thread I have demonstrated that again with the 2600 fps 311466 groups at 100, 200 and 300 yards.

It is unfortunate that you chose not to shoot with me; I think we both may have learned something and enjoyed each other’s company. Should you get out this way I will always extend the opportunity to you?

It has been indeed an interesting discussion.

Larry Gibson

[Larry Gibson]

Digital Dan

I've waited for decades for someone to definitively prove that "sleeping bullets" can group tighter at longer range than short. Ain't happened yet so far as I know.

If and when you do see that happen please let me know because I've been wanting to see it also for a long, long time.

Larry Gibson

[Digital Dan]

I will do that. Do you have a cache of "33"?

[geargnasher]

Fair enough Larry, Re: Post #89, I stand corrected and you have seen enough to accept that the theoretical progression of more perfect system=higher accurate velocity is in fact being proven in the real world by a few people, all the way past 200K.

HOWEVER!!!!! Referencing post #84, I think you're wrong about my target! The flyers are obviously YAWED whereas the clustered holes are ROUND! That was my whole point! The one that was yawed the worst was the farthest away from the main group. I shot quite a few of these in five and ten-shot groups with the same load and tended to have at least one flyer every five shots. The "base nibs" probably didn't cause balance issues, but probably DID cause unrecoverable yaw on occasion, even at relatively high velocity, due to keeping the gas check from staying square under launch pressure. The same thing could have been caused by a major out-of-balance condition of the flyers due to casting defect or defect in launch process, but the holes would likely have been more round depending on which, they just would have been flyers as the RPM threshold for the bad boolits was exceeded.

The RPM threshold can exist at any point depending on quality of load. If you shoot some REALLY "Janky" boolits, it can be lowered quite a bit, too. It just so happens that "normal" loading techniques with standard reloading dies and generic moulds gets us an "average" useable accuracy window around 130K rpm, plus or minus some particulars. One has to step up and correct common tolerance and other issues to progress beyond that. One can be super-sloppy and do worse than the "standard".

Tooling and techniques designed for jacketed bullets that can tolerate a lot of slop without damage get you only to a certain accurate velocity with cast. THAT is the trend the RPM threshold of 120-140K
rpm reflects.

Gear

[MBTcustom]

HOWEVER!!!!! Referencing post #84, I think you're wrong about my target! The flyers are obviously YAWED whereas the clustered holes are ROUND! That was my whole point! The one that was yawed the worst was the farthest away from the main group. I shot quite a few of these in five and ten-shot groups with the same load and tended to have at least one flyer every five shots. The "base nibs" probably didn't cause balance issues, but probably DID cause unrecoverable yaw on occasion, even at relatively high velocity, due to keeping the gas check from staying square under launch pressure. The same thing could have been caused by a major out-of-balance condition of the flyers due to casting defect or defect in launch process, but the holes would likely have been more round depending on which, they just would have been flyers as the RPM threshold for the bad boolits was exceeded.


Gear

Thanks for the clearification Ian. I missed that detail myself till you just pointed it out.
Crazy how a tiny shadow on only one side of a boolit hole can change the whole way you read it!

[cainttype]

I must be missing something.
Larry has attempted to illustrate through multiple posts, for a long time, that this "RPM threshold" is an area where average cast shooters, using average firearms, and employing basic loading procedures are likely to see a deterioration of accuracy as velocities are increased if the standard grease-grooved cast projectile exceeds 140,000 RPM. He has, as far as I'm aware, always maintained that this "threshold" is NOT a limit, and can be exceeded by various means...better casts, better loading techniques, better component choices, better firearms, and better ammo-to-firearm fit.
The theory didn't originate with Larry, as he has explained before, but he has done some serious testing that has obvious interest to the average cast rifle shooter. The simple point that it is EASIER to achieve accuracy with higher velocities by using a slower rate twist is very important to the casual shooter who has no desire to get terribly technical, but likes to enjoy his firearm with a minimum of fuss.
I very much appreciate anyone that takes the time to methodically test anything that interests me and shares their results. Whether I agree with their conclusions is irrelevant, I appreciate their generosity.
By the way, Larry, you're welcome to shoot with me anytime, as are any others that even attempt to dessiminate information in an effort to help others.

[Larry Gibson]

I will do that. Do you have a cache of "33"?

That does seem to be where it all started........with the famous EK.........with two 3 shot groups no less!

Larry Gibson

[Larry Gibson]

Cainttype

Eloquently stated, be glad to shoot with you.

Larry Gibson

[geargnasher]

That does seem to be where it all started........with the famous EK.........with two 3 shot groups no less!

Larry Gibson

OH! with EK, thanks for the edit to clarify, I wondered what you meant.

Gear

[35 shooter]

cainttype...post #94 is exactly the way i've been looking at the rpm theory but you summed it up best. That's exactly the way i've seen Larry Gibson's posts saying all along. I think goodsteal and others are on the right track too by balancing everthing just right to push the speed up more and still maintain accurracy. Kind of like balancing a tire for a car to hold a straight line in the road and go faster, smoother, without shaking things apart. Seems like everybody's on this like buzzards on road kill. They may be coming in from different angles but with one goal in mind.:grin: Goin faster accurrately! I know one thing for sure, with the collective experience on this site, this IS where it will get done if at all!

Larry Gibson your welcome in MS. anytime, as is anyone else that shoots cast boolits.

[JeffG]

Good discussion.

If I may put in my 2 cents worth. Please take it for what its worth. I am not trying to discourage anyone's personal belief about what happens to a boolit in flight, and I'm not asserting my view on this as gospel.

I have mentioned in open forum that I disagree with the RPM theory. I do not argue that it exists at all. In fact, I have observed it in laboratory environment spinning things at high RPM and observing the effect. I only disagree that it always applies within the confines of the speeds we are shooting.
This is what I have seen.
If I make an aluminum cup about 1.5" in diameter, with a cavity about 1" deep with about a 1/8" wall, put it on a high speed motor shaft and spin it up to 10,000 RPM, it will begin to ring at a certain point like a bell, or more like Benjamin Franklin's glass harmonica. It's actually quite deafening. I noticed that this ringing occurred at a very specific rpm. Basically, I made an apparatus that would allow me to audibly hear the rpm threshold being crossed by this cup.
I took more care with the alignment of the cup to the shaft, and observed that I "pushed the rpm threshold up" just as Larry Gibson says.
I kept doing this, and getting the cup more and more perfectly balanced, but what I noticed is that the RPM threshold goes up exponentially to the perfection of the cups alignment to the shaft.
When I finally got the cup nearly perfect in every way, I had it running about .0001 TIR, and we were able to push the RPM up past the 20,000rpm "wall" we were stuck at, up to nearly 40,000 RPM with not a hint of ringing at all.
It was obvious to all observing, that when it comes to spinning things at high RPM and keeping them stable, accuracy and alignment pays huge dividends towards pushing up the RPM threshold, to the point that I postulate it would cease to be an issue for a cast lead boolit or any projectile.

Furthermore, the bell didn't just start ringing all of a sudden. It got louder and louder as we approached the RPM threshold (while it was still running imbalanced), and pushing past it would give an effect where it was no longer ringing per se, but the vibration it put off was impressive etc etc etc.
The point is, the boolit is not either "balanced" or "imbalanced" but there were certain "nodes" of RPM where it liked to exist, and this was observed even when the threshold had been crossed.

My personal belief is that we are able to get a perfectly balanced cast boolit into the barrel, and past the crown, and while the boolit may be damaged, it is damaged in a concentric manner.
This is why I take such pains to align a rifles chamber to the bore, and ream it perfectly straight, and why I have left a bit of flare on the mouth of the case (hey it seemed to work sometimes!) to align the boolit between the case flare and the bore rider.

I think that a given alloy has only so much ability to right itself when thrown imperfectly into a rifled barrel. Copper is able to do this, and PP is able to cushion this, and a sabot just doesn't give a dam.
A naked cast boolit is too week to right itself and it gets damaged upon entry into the barrel, and (if that barrel has hook), upon traverse chamber to crown.
I think that if you can get your system of rifle, brass, barrel, and chamber to be perfectly aligned while under the pressure of firing! it is possible to shoot much faster than a typical rifle is capable of.

Where's you proof?!?!?!? (you might say whilst slapping the table so hard the silverware rattles.)
I don't have any....yet.
I have a bunch of theories posted by the good people (some a little on the prickly side) of this forum, evidence that I have observed with my own two eyes (unrelated? irrelevant?), my wits, and my own theories about these things.

I will have answers someday. If I can get my business up and running, I intend to invest in some testing equipment that is astronomically expensive, and write about my findings.
Now, anybody who disagrees with my opinion and theory is free to do so. I'm hoping that we can all work together so that the truth can be found out, because I have a very strong suspicion that the truth lies somewhere between the lines that have been drawn in the sand.
Many have told me that I'm a fool for getting wrapped around the axle with this issue, but I was already going this way anyway. I could get there a lot faster if each of you people whom I respect (and some whom I love like brothers) would understand that you have no better grasp on the truth than I do, even though many of you have done much more shooting and experimenting than I have.

I believe that it all boils down to the boolits and the pipe. It has been my life's mission for the past three years to make those two things right, instead of dealing with their wrongness, and getting "close enough".
I am satisfied that I can chamber a barrel straighter than anyone else with my eye on cast boolit shooting which is an unforgiving mistress.
Now I am turning my sights towards casting the perfect boolit.

My father is a scientist. His words ring in my ears: change one thing. Turn the crank. Repeat.

The part about not ringing at a specific RPM brings to mind the effect of harmonics and how at a certain RPM they can 'cancel out'. I may not be understanding many things here but wonder if this could this apply to the period of time when the bullet 'goes to sleep'?

[303Guy]

303Guy

Any idea of the velocity?

Larry Gibson
None. I'll have a look at the load data and see if I can infer some velocity range.

[runfiverun]

Good discussion.

If I may put in my 2 cents worth. Please take it for what its worth. I am not trying to discourage anyone's personal belief about what happens to a boolit in flight, and I'm not asserting my view on this as gospel.

I have mentioned in open forum that I disagree with the RPM theory. I do not argue that it exists at all. In fact, I have observed it in laboratory environment spinning things at high RPM and observing the effect. I only disagree that it always applies within the confines of the speeds we are shooting.
This is what I have seen.
If I make an aluminum cup about 1.5" in diameter, with a cavity about 1" deep with about a 1/8" wall, put it on a high speed motor shaft and spin it up to 10,000 RPM, it will begin to ring at a certain point like a bell, or more like Benjamin Franklin's glass harmonica. It's actually quite deafening. I noticed that this ringing occurred at a very specific rpm. Basically, I made an apparatus that would allow me to audibly hear the rpm threshold being crossed by this cup.
I took more care with the alignment of the cup to the shaft, and observed that I "pushed the rpm threshold up" just as Larry Gibson says.
I kept doing this, and getting the cup more and more perfectly balanced, but what I noticed is that the RPM threshold goes up exponentially to the perfection of the cups alignment to the shaft.
When I finally got the cup nearly perfect in every way, I had it running about .0001 TIR, and we were able to push the RPM up past the 20,000rpm "wall" we were stuck at, up to nearly 40,000 RPM with not a hint of ringing at all.
It was obvious to all observing, that when it comes to spinning things at high RPM and keeping them stable, accuracy and alignment pays huge dividends towards pushing up the RPM threshold, to the point that I postulate it would cease to be an issue for a cast lead boolit or any projectile.

Furthermore, the bell didn't just start ringing all of a sudden. It got louder and louder as we approached the RPM threshold (while it was still running imbalanced), and pushing past it would give an effect where it was no longer ringing per se, but the vibration it put off was impressive etc etc etc.
The point is, the boolit is not either "balanced" or "imbalanced" but there were certain "nodes" of RPM where it liked to exist, and this was observed even when the threshold had been crossed.

My personal belief is that we are able to get a perfectly balanced cast boolit into the barrel, and past the crown, and while the boolit may be damaged, it is damaged in a concentric manner.
This is why I take such pains to align a rifles chamber to the bore, and ream it perfectly straight, and why I have left a bit of flare on the mouth of the case (hey it seemed to work sometimes!) to align the boolit between the case flare and the bore rider.

I think that a given alloy has only so much ability to right itself when thrown imperfectly into a rifled barrel. Copper is able to do this, and PP is able to cushion this, and a sabot just doesn't give a dam.
A naked cast boolit is too week to right itself and it gets damaged upon entry into the barrel, and (if that barrel has hook), upon traverse chamber to crown.
I think that if you can get your system of rifle, brass, barrel, and chamber to be perfectly aligned while under the pressure of firing! it is possible to shoot much faster than a typical rifle is capable of.

Where's you proof?!?!?!? (you might say whilst slapping the table so hard the silverware rattles.)
I don't have any....yet.
I have a bunch of theories posted by the good people (some a little on the prickly side) of this forum, evidence that I have observed with my own two eyes (unrelated? irrelevant?), my wits, and my own theories about these things.

I will have answers someday. If I can get my business up and running, I intend to invest in some testing equipment that is astronomically expensive, and write about my findings.
Now, anybody who disagrees with my opinion and theory is free to do so. I'm hoping that we can all work together so that the truth can be found out, because I have a very strong suspicion that the truth lies somewhere between the lines that have been drawn in the sand.
Many have told me that I'm a fool for getting wrapped around the axle with this issue, but I was already going this way anyway. I could get there a lot faster if each of you people whom I respect (and some whom I love like brothers) would understand that you have no better grasp on the truth than I do, even though many of you have done much more shooting and experimenting than I have.

I believe that it all boils down to the boolits and the pipe. It has been my life's mission for the past three years to make those two things right, instead of dealing with their wrongness, and getting "close enough".
I am satisfied that I can chamber a barrel straighter than anyone else with my eye on cast boolit shooting which is an unforgiving mistress.
Now I am turning my sights towards casting the perfect boolit.

My father is a scientist. His words ring in my ears: change one thing. Turn the crank. Repeat.

I quoted this part about the ringing cup just to emphasize why we take the pains to FIT the cases to the rifle as much as we take pains to fit the boolit to the throat.
if you take the TIME to ALIGN the spinning object to the centerline of the tool spinning it YOU WILL HAVE BETTER RESULTS.
NOT JUST IN ACCURACY BUT IN VELOCITY ALSO.
NOT SHOUTING,,, just emphasizing.
once you get past this part, the load development is not much different than for a jaxketed bullet.

[leftiye]

Actually, the lines in the sand overlap. Larry says that the rpm thingie is dependent upon imperfections and imbalances in the boolit. He accepts that. Others of us simply want to concentrate on the imperfections in the first place. In my mind the issue is over because of this. It becomes a chicken-or-egg thing. All the yelling is therefore about? Do you argue about it being the imperfections or do you argue about the important thing being the rpms? The issue in practice is the same then regardless of points that support one view or the other.

I think a lot of the problem is the weakness of lead (or alloys thereof), I think the paper patch blows by the "velocity barrier" because it protects the lead from deformation. I don't think there is a logical argument for defining the issue to disallow paper patches and coated boolits, they simply avoid the imperfections produced in the barrel.

[Larry Gibson]

leftiye

Excellent points. It is a "chicken & egg thing" indeed. That may be a good analogy. The "egg" part is the casting, loading, fitting (as 5R5 mentions), and the launching (internal ballistics) of the cast bullet to keep it as balanced as possible. The "chicken" thing then occurs with the bullet in flight (the external ballistics). The RPM (chicken) then comes into play. The more balanced the bullet is in flight the less the RPM (actually the centrifugal force created by the RPM, the higher the RPM the greater the centrifugal force) has to act upon and the accuracy will be less affected at all ranges. Conversely, the greater the imbalance in the bullet the more the RPM has to act upon and accuracy will be affected to a greater extent especially as the range increases. The trick is to do everything possible, if you want to push up the RPM threshold to a higher RPM/velocity, is to keep the bullet as balanced as possible in all things........be it the "chicken or the egg".

Absolutely correct about the PP also. They do protect the bullet from deformation (leads to imbalance) as does the coating on cast bullets and certainly the jackets of jacketed bullets.

Understanding this, the cast bullet shooter can be blissfully happy getting excellent accuracy at a functional velocity below the RPM threshold with little but ordinary casting and loading techniques. That is where the vast majority of cast bullet shooters are and want to be. On the other hand, understanding what the RPM threshold is and what causes it we (those of us who like to "push" things and meet harder challenges in this endeavor) can move forward. Understanding the problem helps us to defeat the problem.

Larry Gibson

[MBTcustom]

We all learn, and our personal theories change. That goes for everyone here, myself included, but there is only one TRUTH.
I see everyone here drawing closer to the same conclusion and it's getting to the point that all of this will gel. However, regardless of where we have ended up, no one is willing to forget where all this started, and there is deep bitterness about it.

Imagine how much faster the learning process would have been had we all been working together instead of fighting like a bunch of 6 year olds.
Imagine what would have happened if each one had been willing to consider that there is a grain of truth behind all the bluster and hard mindedness of the other.
Imagine what would have happened if some had extended a shred of effort to make their viewpoint a little more palatable to those who would not readily accept that viewpoint, instead of slapping it on the table like a dead fish and saying "take it or leave it" or making the understanding of their view a thousand yard crawl over broken glass.
Imagine how much faster things could have progressed had the validity of peoples claims been accepted instead of questioned and proof demanded.

Some people here seem to exist only for the purpose of stirring the pot and keeping factions set against one another. It's no longer about the science or the fun of the sport, it's about the soap opera that can be generated in the midst of it, and too many members have fallen for it hook line and sinker.
I have not, and I'm here to tell you that if any of you think you have it all sewn up, and know every important thing there is to know about shooting cast lead, you are badly mistaken. Any of you who think that another member in this fight has nothing to offer, you are badly mistaken.

I know each of you, and have had a good rapport with each one (I hope) and I have tried to encourage you all to advance the general knowledge of this sport by working together.
Unfortunately, sometimes it seem that settling old scores is more important than finding out new information, and teaching the next generation so that the knowledge isn't lost........again.
I'm here to teach and to learn, and this old scrap is getting in the way of that. Not just for me, but for everyone.
If anyone didn't like the way this thread went, you sure as heck aren't going to like what happens the next time a fight starts.
There are lots of forums that are unmoderated, but this isn't one of them. If anyone is just so course and foolish that they just have to fight and tell somebody what for, then you can go to any gun forum that I am not a moderator on and have at it. Just remember to check your BS at the door.

I have been accused of being partial by people who are in no position to sit in judgment, because they have tried to jade me against their enemies, or bully me into a sympathetic judgment, and couldn't look at this issue objectively if their life depended on it. I have not given an inch one way or the other (although I have listened to every opinion), but I have gotten a good education on where everyone stands.
I don't like fighting, and I refuse to hate anyone, so when I have a problem with something I settle it real quick and dirty like.
The HS cast lead boolit is the direction I am personally pursuing, so I'm reading everything I can on the subject anyway. It's time to scrape some fog off the glass, and I think it's going to be better for everyone.

It's going to be an interesting year.
Thank you.

[geargnasher]

I quoted this part about the ringing cup just to emphasize why we take the pains to FIT the cases to the rifle as much as we take pains to fit the boolit to the throat.
if you take the TIME to ALIGN the spinning object to the centerline of the tool spinning it YOU WILL HAVE BETTER RESULTS.
NOT JUST IN ACCURACY BUT IN VELOCITY ALSO.
NOT SHOUTING,,, just emphasizing.
once you get past this part, the load development is not much different than for a jaxketed bullet.

Boolit jump and the way the cartridge does or doesn't load the breech face are also things to consider that are closely related to the origin of consistent, repeatable system vibrations. Since pressure is initially applied to the gun via the cartridge case, having the same fit conditions of brass to chamber ensures the repeatable transfer of force from the cartridge to the rest of the system.

Gear

[popper]

initial instability is caused by bullet yaw as it leaves the muzzle, right - interesting thought. So a properly spun 'perfect' boolit good/bad base should stabilize downrange and NOT make any difference? Only the radii of the helix would change? I damaged the base of some 40s a while back, they made a nice circle around the POA. Unfortunately I didn't mark the damage point & shot at a fixed distance. Question is: does that alter group POI or separate POI? Gear's target post would seem to indicate it alters the group POI. Those 2 are too close together to be random, but I am assuming the 'kilter' was unknown. Would POI have straightened out at longer range? There isn't much tipping. Saw a guy shoot some Aquila sub 22LR, old slow twist rifle @ 50. His target had vertical stripes.

[Digital Dan]

Popper, I'd think a shift in group POI would result only if the inconsistencies are consistent, ie. if several bullet bases are equally deformed and launched from the same relative position relative to chamber and bore axis. Otherwise I'd expect a "separate" POI, or greater dispersion. If you recall earlier in the discussion there was a picture of a group fired by a .303 Enfield in which 3 bullets were closely grouped and there were two flyers? The flyers indicate tipping based on leading marks on the target. Of the 3 tightly grouped, two had symmetrical holes and a third indicated tipping as well. I would call the third an instance of coincidence more than anything else.

On another point, I'd not expect a bullet with any imbalance or inconsistency of form (damaged base or nose) to stabilize sufficiently to present small groups. The initial pitching and yawing motion induced on a bullet as it leaves the muzzle is caused by a multitude of factors and whether or not they null over the course of flight is contingent upon cause. The basic battle is between gyroscopic stability versus aerodynamic forces. Both are variable in their interaction. They are also more of a consideration with tightly twisted barrels and bullets fired at long range having boat tails and VLD nose forms. It's complicated....

[milrifle]

As a novice cast bullet shooter, how can I determine whether my accuracy problem is due to imbalance, or stripping the rifling? When I first started casting, I guess I was disappointed that I couldn't shoot cast as fast as jacketed. I was thinking SURELY, I could get my 03-A3 to go AT LEAST 2000 fps. But as I inched up on the charge, all of a sudden I wasn't even on the paper. What the heck? I do some reading up and come to the conclusion that I must be stripping the rifling. I began to water drop my COWW, but I also began to get used to shooting at 1750-1800 fps and quit trying to push them so hard (Maybe I grew up?). After reading this, I wonder if maybe imbalance was my problem? Short of recovering an undamaged bullet to examine the rifling, how can I tell?

[Green Lizzard]

good stuff on this thread by a lot of smart people. i have no interest in hi-speed cast, but i think there is a lot of stuff in here that can help us guys that like to play at 1650 to 2000 fps. now as far as imperfect or damaged boolits go i think i have the ultimate boolit. i have been playing with an 1889 swiss 7.5x54.5 bore is .296 groove is .307 total boolit dia. is .323. lyman 314299 at .314 patched to .323. this thing should be a misshapen blob of lead with trailing fins, but it shoots great. throat is .600 long shaped like a funnel. do you think its all in the (funnel)? how in the world can this thing be accurate. by the way its very close to the service round

[Larry Gibson]

milrifle

Your bullets were not "stripping" on the rifling, especially the alloy and at velocity you mention, regardless of what you may have read. There is a whole lot of disinformation on that, especially on the internet. As you can see many of us shoot naked cast bullets well above your velocity with very good success. What you came up against with your bullets and load was the RPM threshold. To push higher, assuming good cast bullets(?), you must change something about the load and the bullet.

Why don't you start another thread specifying the bullet/load and rifle so we can assist? If that's what you want to do.

Larry Gibson

[RoyEllis]

I don't know all there is about much that has been posted & discussed in this and other threads, but I've learned a lot & got some fodder for serious thought. I would share a couple of quotes though...

What we see depends mainly on what we look for. 1st Baron of Avebury, John Lubbock

Whenever ideas are shared, the net result is always far greater than the sum of it's parts. Rich Willis

:bigsmyl2:

[popper]

Digital Dan - that pic is the reason for my question. Did a lot of testing with the 40 (1:16) and found LLA shot (IIRC) high, Recluse did high left, PC is right on (fixed sights). So if the 2 flyers were not called, why are they close together, i.e., would 'bad' boolits group at the second location? If POI changes with lube, why not 'bad' boolits?

[geargnasher]

Just for amusement.....



Loaded and shot another five today, interesting results and I have a few more basic questions. I backed off to 48 grains of RX22 and added a weighed 1/2 grain of Dacron all else the same. The upshot was the confetti was now violently twisted strips, like crepe paper but spirals, and the lube that accumulated in the depressions of the grease grooves was preserved perfectly on the strips, little lines of clean lube. Obviously the Dacron helps the seal, as it often does with bare GG boolits even with gas checks.

I know you really can't tell much from five shots, but look carefully at the first three in the string. All elliptical holes, all elliptical the same direction, all strung to the left. Then the last two round ones right together under the POA. I'm about to give up entirely on this boolit, it's been unstable at any speed in any gun in which I've fired it. If I could figure out how to keep it pointed straight ahead, I think it would group.

Now questions. Has anyone had accuracy problems that they attributed to lube in the grooves on the outside of the patch? Also, do we think that patched bore-riders are a bust because the paper doesn't get sliced through on the nose and so they don't always shuck the patch properly?

http://castboolits.gunloads.com/imagehosting/thum_89094e0a71a1d983d.jpg (http://castboolits.gunloads.com/vbimghost.php?do=displayimg&imgid=1314)

Gear

Gear

[Green Lizzard]

gear thats my theory on the bore riders, have had no fun there

[SgtDog0311]

Here's a neat one, shows what happens when you are pushing boolits way past the comfy velocity zone and screw up the QC on two of them somehow. I think I had some sprue nibs on some of these from a loose plate and I didn't cull them well enough. The whole batch would do this tight/yawed flyer thing, lube not withstanding, which is what I was testing at the time. Anyway, if all five had been as badly balanced as the two flyers, you can see what the group would have done. BUT, three of them were done right and held true even going well past the "RPM Threshold". Most of the time my groups either totally suck or pack in tight depending on how well I walk the tightrope at high velocity, this one was split.

http://castboolits.gunloads.com/attachment.php?attachmentid=62346&d=1361757719

I have some Duesie pics of what the 266469 will do out of a .270, paper patched, due to the under-bore core, but they are saved on another computer and lost from here in the image-hosting fiasco from a couple years ago. Horizontal strings of identically-oriented elliptical holes; looked like I had thrown little frisbees through the target. Might still have the target but I didn't notice it in the .270 binder earlier.

Gear

Probably few here less experienced than myself with these concepts but I’m reading them with interest and asking myself a lot of questions.

One question I’d have from this target in relation to the RPM threshold, is what might be your conclusions were you to dramatically drop velocity with the same sample of bullets and have similar prints.

I ask, because I experience this -- what I call a full-house target. I could pull up several three-of-a-kind cloverleafs next to a close pair, and do that from more than one caliber I shoot. I always wondered at the cause - which is not likely an RPM threshold.

My target range is, generally speaking, between 1200 and 1500fps. If I’m understanding the discussion at all, then I’m not hitting any RPM threshold at that those velocities, right?

So if it’s another phenomenon I’m unfamiliar with or the result of some other basic explaination, then what might that be, and might it be present with the target results shown here???

[Digital Dan]

Popper, POI is likely to change in my opinion, but it should be random IF the bullet flaws are randomly oriented in the chamber. If they are consistent in nature and orientation they may group well.. To another POI.

[SgtDog0311]

Had to post this since it was in the back of my mind the minute I started reading this thread yesterday:

I know from reading the links that we’ve sort of took Epicyclic Swerve out of contention for an explanation of ‘angularly smaller groups at longer ranges’ but the discussion peaked my interest in light of a recent range exercise that left me shaking my head. Mind you, as noted in my previous posts this is not at RPM limit pushing speeds, and they are not high-end jacketed bullets either. Just my own home-rolled 32-40s from an LBT mold. And I realize the shot count does not meet the sample size Larry mentions, being only five shots but such as they are…

I applied as much control during the shooting of these as I’ve applied to any grouping attempt and was perplexed at the outcome. At the time, I did not have benefit of any theoretical attempts to explain it. This had happened to me once (maybe twice) before too but I can’t remember which rifle it was… blamed it on myself at the time so dismissed it from recall.

If I’m understanding the use of the work ‘angular’ and the use of the word ‘dispersion’ properly then I would have thought the 50yd target would have translated to a 4” angular dispersion at 100yds.

But from the 100yd target you would have calculated 3&9/16s”, almost precisely what was printed. So, it does appear the bullet went to sleep between 100 and 150yds but was experiencing some instability yet at 50yds. Quite interesting!

[MBTcustom]

John, that would be a good one to take out and test more thoroughly. If I were you, and considering what has been posted here, I would load up 50 of those babies and fire 5 ten shot groups at progressive ranges to see if what you are seeing really is repeatable.
Not challenging your groups in any way, just curious is all.

[SgtDog0311]

Think I will Tim... I still have 50 of the same load so its just finding the time and a sled. I rarely use one but did borrow one this summer for load development at the cabin with several rifles, the 32-40 being the subject here. That is one reason I was confident enough to post the groups -- but a larger sampling might show something different. Even if repeatable with this load, I think it would be of additional interest to see if a slower powder would then produce a similar result.

Sure been an interesting read. Told my buddy who turned me on to this thread that I had to get up every few minutes and gaze out the window and think about something else whilst my brain-matter got back to a simmer.

[Larry Gibson]

Some days are diamonds, some days are stones............today was a definitely a diamond...........:guntootsmiley:

I had 15 shots left from the box of 311466 loads I shot the previously posted 100, 200, 300 yard test with. The stated 2600 fps stated was about what that load chronographed at (15" from muzzle) a year and a half ago when I was still up in Washington State. I was doing some other testing today so decided to chronograph a 10 shot string of the remaining ammunition just to see what it actually does down here in Arizona. Shown is the 10 shot group of .855" at 100 yards and the Oehler 35P printout of those 10 shots. After shooting the group I wished I had shot it at 300 yards! However, that 100 yards group is self satisfying to say the least, especially at 2614 fps.........:drinks:

Larry Gibson

93142

[Green Lizzard]

i need a 1 in 14 30 cal, that is a great group larry

[TheCelt]

That is an awesome group Larry!!!! To me, MOA is doing something, MOA at those velocities is astounding!!!! Well done Sir!!

[35 shooter]

I'd go huntin with that load any day! Plus 2600 fps? That's good shootin for a hot cast boolit load! Now that's where i'm trying to get. If i ever get my rifle shooting that tight that fast, i think i'll have it gold plated!:grin:

[Digital Dan]

Skill and cunning will prevail over fear and superstition every time.

Nice shooting LG!

[swheeler]

Now that is what I call a group, very good Larry!

[Doc Highwall]

Larry, what are the particulars of that load?

[MBTcustom]

Larry, I'm looking at all those groups you posted, and it seems like the boolits are impacting nose up at 100 yards, and straighten some at 200 but are flying through the paper straight at 300.
What do you make of that?

[Larry Gibson]

Goodsteel

The target frame holders at the range (Sara Park in LHC) are cement with slots in them. The frame legs are 2x2s so when in the slots they are a soppy fit at 100 and 200 but a tighter fit at 300 Yards. There are wood wedges to hold the frames tight so they don't flop in any wind. Thus most of the targets lean slightly toward you or away from you. How much depends on the fit of the legs in the slots and the fit of the wedges. I place the 100 and 200 so they lean towards the bench. At 300 yards the frames are pretty much straight up. At 100 and 200 yards I can get the same effect of the small smudge on the bottom of the bullets holes on the top of the holes simply by leaning the target back. I was shooting those tests on the left end of the firing line. When I shot that group yesterday I was toward the right of the firing line and had a frame, cement slot and wedges that stood the target straight up. Note the lack of smudges with the same load (?) but it's hard to tell.

Another thought....the 311461 is a Loverin design and I do fill all the lube grooves with lube. We do know the lube spins off so I wonder if perhaps at 100 and 200 yards that is simply lube expanding out of the grooves a bit but still held in by the air pressure? By 300 yards it is gone? Beats me but they sure do shoot nice:-D

Larry Gibson

[Larry Gibson]

Larry, what are the particulars of that load?

Not a problem.

The 311466 is from a 4 cavity Lyman 311466U. Alloy is 80/20 linotype/lead and WQ'd. BHN is running 28 - 30. They drop at exactly .311. I do two visual inspections for defects. One is a quick inspection after the bullets dry and then a second more careful inspection before I GC and lube. Any defect, even the slightest, is cause for rejection. I am pretty picky here and run about a 20 - 30% rejection rate. Probably to picky but it seems to pay off as any surface defect will cause the greatest imbalance. The bullets are not sorted between cavity nor are they weight sorted.

I use a .311 H&I die in the 450 lubrasizer to lube and GC w/o sizing. My initial HV test was done with a 2 cavity Lyman 311466 though which dropped them larger which did require sizing. I used a Lee .311 push through sizer seating the GC and sizing on those and then lubed in the .311 H&I in the 450. Lube in the initial tests was Javelina and Tamerack (both NRA 50/50 lubes) and 2500+ all of which worked equally well. I had no leading at all.

The cases initially used were match prepped LC92s (which I mistakenly put in the previous post) but switched to Winchester .308W Palma cases for a bit more powder capacity. The cases are well fire formed but were match prepped also and necks uniformed. The necks are sized for .002 - .003 tension in a Redding bushing die.

Primers are Winchester LRs.

Powder is AA4350. I tried a bit faster powders (4895, 4064, Varget and RL15) acceleration was still to quick. Of the slower powders (RL19, AA4350, H4350, IMR4350, H4831 and RL22) I found AA4350 to give the best accuracy at 100 - 105% load density. Of course other rifles may prefer a different powder. BTW; all powder charges are thrown with a Lyman 55 powder thrower. I use the knocker twice to settle the powder in the drum on each throw. That gives a consistent and less than +/- .1 gr charge. The powder charge is 49 gr AA4350. That comes up a bitt into the neck and I tap the case several times on a lead block to settle the charge to just above the case neck/shoulder junction.

I use a Lee .308W seater which allows a slip fit of the .311 bullet up into the seating stem. I slightly contoured the stem to fit the 411466 nose. Cartridge oal is 2.585 which has the front driving band just kissing the leade and the top of the GC still in the neck. The powder charge is slightly compressed. Run out measured on the front driving band runs .000 - .004 with most (85 - 90%) under .002. Most of the rest run .002 - .003 with a couple approaching .004. So far I've seen no accuracy difference with the .004s compared to those with .000 run out. At the acceleration rate of these rounds it seems the difference is a non issue as other things come into play overshadowing any affect the run out may have.

Note on alloy; that 80/20 alloy does very well up through 2500 - 2550 fps w/o HT or WQing. Above that acceleration to higher velocity and flyer show some bullets are being imbalanced and are over the RPM threshold for them. I have pushed to 2650 -2700 fps with Babbitt added (thanks BadgerEdd) but the load is severely compressed at 50 and 51 gr AA4350.

Larry Gibson

I should add that the tested (using this same Palma rifle with the Oehler M43) psi of this load runs 40,000 - 41,000 psi(M43).

[swheeler]

Larry you don't say but was the barrel left seasoned from previous test, or did you start with cleaned barrel and couple fouler shots?

[Larry Gibson]

Larry you don't say but was the barrel left seasoned from previous test, or did you start with cleaned barrel and couple fouler shots?

With this load the first shot from a clean barrel goes 7 - 12" out in random directions at 100 yards. Second shot is to group. I'm casting some more bullets today and testing this very thing. I just ran a clean dry patch through the barrel from yesterdays shooting. Bore is shiny and little carbon came out on patch, absolutely no leading. I will test the dry patched bore a few times unless the 1st couple are out there also. Then will leave the bore completely fouled. Much dryer down here w/o hardly and humidity compared to Puget Sound area of Washington. Definitely need to see what effect that has on 1st shot.

Larry Gibson

[swheeler]

I want to thank you for sharing ALL this information with the members here. I am sure many here appreciate your tests that are always documented clear. I just have to save up and invest in a slow twist barrel, why fight the rpm monster and fail when you can beat him with a stick, a slow twist stick.

[Nrut]

Larry,
Congrats on your fine casting, loading, and shooting..
Also thanks for the info. posted in post #129..

My questions are:
1. Did you use a dipper or a bottom pour pot to cast your bullets?

2. IIRC your slow twist rifle has 26" barrel which is akin to using a varmint rifle for the area that I hunt..
What kind of performance do you get out of shorter barrels?


As aside I finally came to the conclusion in the last couple of years that a 45-70 is the best solution hunting in the area that I hunt and I have that covered along with the 9.3 and .35 calibers..

But I still find cast at high velocity extremely interesting..

Also am of the same belief that leftiye posted in post #102..
Excellent post leftiye!..

Won't be rebarreling to slower twist for just the sake of hi-vel..
Instead will work more on improving my casting skills and reloading skills as I suspect most here will or are doing..

[Larry Gibson]

Nrut

Larry,
Congrats on your fine casting, loading, and shooting..
Also thanks for the info. posted in post #129..

My pleasure to share all the info I can.

My questions are:
1. Did you use a dipper or a bottom pour pot to cast your bullets?

I used a bottom pour furnace; Lyman Mag20. Alloy temp was maintained at 725 +/- 10. I filled each cavity separately leaving a good rounded sprue on each.

2. IIRC your slow twist rifle has 26" barrel which is akin to using a varmint rifle for the area that I hunt..
What kind of performance do you get out of shorter barrels?

Actually the Schultz & Larson Palma barrel is 27.5" long. I've no experience thus far with a .30 cal 14" twist shorter barrel. Of course a shorter barrel would reduce velocity. My next slow twist will be a 26" heavy sporter barrel with 16" twist chambered in the 30x57 (30 XCB) cartridge. The 311466 will be fully stabilized down at 2100 fps in it but I intend to push that bullet to 2700 - 2800+ fps so stabilization is not going to be a problem. The increased cast capacity of the 30x57 over the .308W should allow that with one of the slower powders while maintain the same 40,000 psi give or take. If it doesn't then I can rechamber easily to '06 which will definitely have the case capacity. The action I'll build it on is already an '06 so that is not a problem and is a built in solution should the problem arise.

The RPM of the last posted load was 135,000. With a 16" twist the velocity would have to be 3000 fps to equal that. However, we know that the imbalance caused during acceleration is not linear to the velocity/twist ratio. The faster we push a cast bullet the lower the RPM threshold becomes. Thus I am realistically looking at the 2700 - 2800 fps with the 30x57 case capacity and a 26" barrel.

Besides pushing up the boundaries on cast bullet velocity my real purpose for the rifle is to have a potential 400 yard deer/antelope/coyote cast bullet rifle.

As aside I finally came to the conclusion in the last couple of years that a 45-70 is the best solution hunting in the area that I hunt and I have that covered along with the 9.3 and .35 calibers..

But I still find cast at high velocity extremely interesting..

I appreciate that and still have my Siamese Mauser in 450-400-70, my 375 H&H M70 and my 35 Remington M91 Argentine Mauser to hunt big game with. Since most big game is killed on the short side of 200 yards they all suffice quite nicely. All are excellent for hunting big game with cast bullets at easily achieved accuracy in the 2000 - 2400 fps range.....mostly because they have slow twists to begin with (at least mine do) that allow that velocity with accuracy easily achieved.......not counting the recoil with the 450-400-70 :wink: However, I do hunt some area's, especially for antelope and coyote, where out to 400 yards is a possible if not probable shot. Thus the quest for cast bullet HV with accuracy. I also go the other way; .......ought to see my 323471s putt along at 390 fps out of my 8x57 Mauser, yes you can literally "see" them:-D

Also am of the same belief that leftiye posted in post #102..
Excellent post leftiye!..

Won't be rebarreling to slower twist for just the sake of hi-vel..
Instead will work more on improving my casting skills and reloading skills as I suspect most here will or are doing....

I also concurred with leftiye as I stated; "Understanding this, the cast bullet shooter can be blissfully happy getting excellent accuracy at a functional velocity below the RPM threshold with little but ordinary casting and loading techniques. That is where the vast majority of cast bullet shooters are and want to be. On the other hand, understanding what the RPM threshold is and what causes it we (those of us who like to "push" things and meet harder challenges in this endeavor) can move forward. Understanding the problem helps us to defeat the problem."

You notice I've not listed all my other rifles and milsurp rifles for sale(?) as I still intend to cast bullets to shoot in them. Some will have meticulously cast and sorted bullets for pushing things as far as I can with those rifles. The others, most of them, will have generic quality cast to be used at a useful and easily found accurate velocity under the RPM threshold because that's all I want to do is shoot them as evidenced by the recent .223 AR loads and results I posted on another thread. Those loads serve very well. They are also the kind of loads that almost all cast bullet shooter want to use with the rifles they have. That is fine. Understanding how to go beyond that is beneficial as it can save a lot of frustration......been there and done that.......

:drinks:

Larry Gibson

[303Guy]

Does this thread qualify as a sticky?

[swheeler]

I would say it should

[geargnasher]

The RPM of the last posted load was 135,000. With a 16" twist the velocity would have to be 3000 fps to equal that. However, we know that the imbalance caused during acceleration is not linear to the velocity/twist ratio. I'm glad to see you address this, because just slowing twist rate isn't the whole deal. One must still keep the boolit from getting too damaged during launch or it's RPM threshold will be relatively low and limit the velocity at which good groups can occur. The faster we push a cast bullet the lower the RPM threshold becomes. THIS is what I've been trying to sort out for the past two years or so. I think the torsional stress on the boolit from the rifling is what causes this "law of diminishing returns". Once the angular acceleration of a given alloy (or jacket, be it paper or plastic) is exceeded then accuracy, again, begins to fall apart. Thus I am realistically looking at the 2700 - 2800 fps with the 30x57 case capacity and a 26" barrel.

Besides pushing up the boundaries on cast bullet velocity my real purpose for the rifle is to have a potential 400 yard deer/antelope/coyote cast bullet rifle. Might do it with a 150 -grainer, wouldn't that be fun? Coyote medicine for sure.



I also concurred with leftiye as I stated; "Understanding this, the cast bullet shooter can be blissfully happy getting excellent accuracy at a functional velocity below the RPM threshold with little but ordinary casting and loading techniques. That's it in a nutshell. That is where the vast majority of cast bullet shooters are and want to be. On the other hand, understanding what the RPM threshold is and what causes it we (those of us who like to "push" things and meet harder challenges in this endeavor) can move forward. Understanding the problem helps us to defeat the problem." I think of the RPM limit of the boolit itself, or perhaps the system, not a fixed number per se. I said "limit" because, in practice, there are LIMITS to each, individual system. "The" RPM limit may or may not be in the theoretical, standard-casting-and-loading-practices 120-140K range. It may be more or much less, but ANY boolit, in the condition it finds itself after it gets out of the muzzle, has a distinct limit to how fast it can be spun and still hold course.

You notice I've not listed all my other rifles and milsurp rifles for sale(?) as I still intend to cast bullets to shoot in them. Some will have meticulously cast and sorted bullets for pushing things as far as I can with those rifles. The others, most of them, will have generic quality cast to be used at a useful and easily found accurate velocity under the RPM threshold because that's all I want to do is shoot them as evidenced by the recent .223 AR loads and results I posted on another thread. Those loads serve very well. They are also the kind of loads that almost all cast bullet shooter want to use with the rifles they have. That is fine. Understanding how to go beyond that is beneficial as it can save a lot of frustration......been there and done that.......

:drinks:

Larry Gibson

This is good. All that remains is finding some way to discover what is happening to ruin our accuracy at high velocity. Getting the RPMs down helps raise accurate velocity potential, but it isn't the thing that ultimately sets the speed limit. It seems that WD 50/50 gives up around 23-2400 FPS even which a lot of tricks, though my 12-twist rifle seems to be able to do a bit more. I've discussed this at length with Goodsteel and several others, we're determined to get to the bottom of it eventually. I think our principle challenge, once fit, load, and vibrations are worked out, is land pressure, but that's a topic for another thread dealing with internal ballistics.

Gear

[45 2.1]

All that remains is finding some way to discover what is happening to ruin our accuracy at high velocity. Getting the RPMs down helps raise accurate velocity potential, but it isn't the thing that ultimately sets the speed limit. It seems that WD 50/50 gives up around 23-2400 FPS even which a lot of tricks, though my 12-twist rifle seems to be able to do a bit more. I've discussed this at length with Goodsteel and several others, we're determined to get to the bottom of it eventually. I think our principle challenge, once fit, load, and vibrations are worked out, is land pressure, but that's a topic for another thread dealing with internal ballistics. Gear

Keep on trying Gear........ you would do better reading past posts though because it is there....... you just can't see it.

[Larry Gibson]

Geargnasher

Might do us well to take a hard look at past experience; the why and the success of controlling the RPM of bullets. It's not with cast bullets but with jacketed I am going to refer to. Consider the "why" of the slow twist long .308W/7.62 Palma barrels used? Some years back the Palma rules allowed teams to bring their own rifles (based on a service rifle action of the visiting nation or the host nation) and with a weight limit. Other than they must have iron sights the cartridge had to be provided by the host nation and was to be of that nations 7.62 NATO Ball ammunition with a 145 - 155 gr FMJBT jacketed bullet. Suffice to say the quality of most 7.62 NATO ball is not up to match standards for 800, 900 and 1000 yard match level shooting.

The problem with military production ammunition is the quality of the bullets. The accuracy standards for the bullets certainly weren’t close to commercial hunting bullets and certainly nowhere close to match bullets. So what was the difference in “quality”? The difference was simply the jacket thickness was not consistent as the jacket was drawn from the billet of brass or copper. Also the lead cores were not consistent in weight. Thus with jackets thicker on one side of the bullet than on the other and lead cores of various weights the bullets had built in imbalances. They were certainly good enough to produce enough to produce sufficient accuracy for large targets but not for precision match shooting.

When Palma matches were reinstituted using the 7.62 NATO cartridge the first matches required the shooters to use military rifles of current issue provided by the host nation. It was quickly learned the 10” and 12” twists over spun (not to be confused with “over stabilized”) the bullets and accuracy wasn’t all that good at 800, 900 and especially 1000 yards. The rules were changed allowing the teams to bring rifles to the matches but the host nation still provided the 7.62 ball ammunition. The rules were lose enough that match accurized rifles began being used.

Some understood the need to slow down the RPM to mitigate some of the adverse affects of the centrifugal force on the ball 7.62 bullets. Thus barrels with 13 and 14” twists became common. Additionally the need was seen to increase the velocity to lessen wind drift and to ensure sufficient retained velocity (sonic) at 1000 yards. This was needed because some nations using the FN/FAL and the G3 did not load the 7.62 NATO up to full NATP velocity specification. Thus the slower twist and longer barrels (28 – 32”) barrels lowered the RPM and increased velocity. My tests reveal in my Palma rifle with the 27.5” barrel and 14” twist that most M80 ball will pick up 100+ fps and accuracy will be 1 – 2 moa for 15 shots; the same as shot at each range in the Palma matches. Similar test of the same ammunition in very accurate match rifles using the same lots of M80 ammunition show the 10” twist barrels give 3 – 4 moa accuracy and the 12” twist barrels 2-3 moa accuracy.

The obvious benefit of the slower twist barrels was to reduce the adverse affect the centrifugal force had on the bullets given imbalance simple by reducing the RPM thereby reducing the centrifugal force. A simple way to use the laws of physics and the laws of ballistics to our advantage. Thus by learning from the past we have success today as evidenced by the results I’ve demonstrated using the slower twist barrel.

I’ve also shown some insight into the need for selecting the right bullet, the right alloy, the right casting technique, a good lube, the right sizing, the right powder and the correct loading technique among a few other things, all not necessarily out of the reach of an experienced cast bullet reloader. You are quite correct that it is not “all about” using a slow twist barrel but also about improving the internal ballistics. I have mentioned this many, many times so 45 2.1 is also correct that "reading past posts though because it is there" might be helpful.

We must also understand that regardless of the closeness of concentric tolerances that we can align, tune and refine the action mating to the barrel or how concentric we cast and load the bullets that at some point we will push that bullet beyond it’s structural limitations and it will become imbalanced in the barrel. Certainly we can stay down in a safe acceleration range where the bullet may be launched perfectly balance and accuracy is excellent. We do that now. However, when we really push a naked perfectly .30 cal cast bullet out of that perfectly tuned and concentric action/barrel/rifle from 0 to 2600 + fps in a 26 – 30” barrel then we have to understand that the laws of physics are severely working against the structural strength of the bullet. I think we are all agreed on that.

So, then perhaps another thread on internal ballistics is indeed in order so that we may read and understand what has been posted and perhaps condense it down to some level of coherency?

Larry Gibson

[Regnar]

Want to learn? Stop reading this, and read the darn book!
Seriously, great book. So easy, a caveman could do it.

[TheCelt]

Want to learn? Stop reading this, and read the darn book!
Seriously, great book. So easy, a caveman could do it.

Beg to differ Regnar, reading is fine but real world applications often differ from what is postulated in books/magazines. I have followed several threads that deal with external ballistics and have learned something from all of them. What differs is that documented results with all parameters listed often departs significantly from what is written they "should be".