RPM Threshold barrel twist/velocity chart

[Eutectic]

A test with a gain twist would probably prove interesting but what should the final bullet rotation be?

Since we already know we shoot higher velocity in slower twist barrels with cast bullets why bother with the gain twist? Why not just use the slower twist?

Larry Gibson

I believe it's the small number on the gain... In other words a 16-10 gain twist would achieve a 10" RPM rating....

I see the big advantage being at the start especially if the 'gain' allowed full engraving at a good reduced twist rate. Be 'maybe' better with heavy weights if case capacity will push them to high velocity?

It would be nice in this equation though; sometimes the solution isn't where it is expected....

Eutectic

[dtknowles]

In theory, because the reason for using a slow twist is so that the boolit is damaged less during launch. Ie. you can push up the RPMTH by delivering a less damaged boolit to the crown.
The big expensive question is: Which damages the boolit less? a 16 twist, or a 15-10 twist?
My money's on the 16 twist, but we'll never know for sure until somebody pony's up some serious cash.
Seems I read somewhere that the gain twist was tried and the results were demoralizing, but I can't remember which book I read that in.....

a more fair comparison would be a gain twist that starts a zero and ends at the muzzle at a 16 twist compared to a straight 16 twist. Which do you think would damage the bullet more? Both should stabilize bullets of the same weight. The reason to go with faster twists is to shoot heavier bullets. I am pretty sure a 16 twist will not stabilize a 220 gr. bullet in 30 cal. I think even 180's would be iffy.

Tim

[frnkeore]

Goodsteel says:

Larry even offered in good faith to meet one member while he was in that members state and was turned down flat like he was scum.

Blanket statements aren't good! I want to clear up my part of the above statememt, whether it's OT or not!

larry offered and I invited him to come to my range here in Oregon, to shoot in front of other witnesses. He said that he still travels back to WA and it's right on I-5. I have not resended my offer and larry has not taken me up on it since that time.

Frank

[frnkeore]

Regarding gain twist, the formost maker of gain twist in North America is Ron Smith of RKS barrels in Canada. I shoot with him at the yearly match that I attend in Spokane, WA. In general, his barrels double the twist rate.

He says that the gain offers no advantage in accuracy but, in high power, with jacketed bullets, the barrel life is approx. doubled. His barrels win most of the schuetzen matches in the West and he says that the reason that his barrels have a advantage in cast is the sight choke that he puts in them.

Frank

[Larry Gibson]

Goodsteel says:


Blanket statements aren't good! I want to clear up my part of the above statememt, whether it's OT or not!

larry offered and I invited him to come to my range here in Oregon, to shoot in front of other witnesses. He said that he still travels back to WA and it's right on I-5. I have not resended my offer and larry has not taken me up on it since that time.

Frank

I haven't been up there since that offer was made. I don't travel on I-5 from here to WA or back so you are out of the way. I made the same offer to you to come down here.......is that supposed to mean something that neither of us made it? No, it simply means we will shoot together when I can make an effort to get to your location sometime.

Besides, goodsteel was not referring to you.

Larry Gibson

[frnkeore]

I haven't been up there since that offer was made. I don't travel on I-5 from here to WA or back so you are out of the way. I made the same offer to you to come down here.......is that supposed to mean something that neither of us made it? No, it simply means we will shoot together when I can make an effort to get to your location sometime.

Besides, goodsteel was not referring to you.

Larry Gibson

Since the person wasn't named or that it isn't someone in this discussion, I just wanted to make it clear that it wasn't me.

Frank

[Larry Gibson]

frnkeore

No, it wasn't you. But to our previous discussion here's what you actually said; "A quick little reply lary and then I am acually done with it!" (where's the spelling Nazi's when you need them) I took it to mean you didn't want to chat with me anymore.....apparently you do?

Well if so then to the point; You just don't get it do you? This thread is about pushing a ternary alloyed cast bullet to as high a velocity as possible while maintain a certain level of accuracy (2 moa or less). All of your quoting of CBS match results tells us nothing we don't already know; yes you can push the RPM threshold to 160,000 RPM quite successfully. We've been doing that for some time. The point of the CBA matches is accuracy only; they don't care what the velocity is. Velocity with accuracy (not match winning accuracy but accuracy) is our purpose/goal here. What part of that don't you understand?

The idea is to push to as high a velocity as possible regardless of the twist. If you'll bother to go back a few posts and look close at the 2620 fps groups you'll see what the goal is. While we appreciate your love for CBA match results that level of accuracy at that low of velocity is not the goal here. Get it?

Now you apparently have an interest, an ability and some equipment. So why not do something constructive for a change? I believe you have a M98 in 8x57 and a very good Loverin mould? Why don't you give us ten 10 shot groups shot at 100 yards covering 1600 fps to 2400 fps with; a faster burning powder such as 4227, 2400 or even H110 and a medium burning powder such as 3031, 4895, 4064 and with a slower burning powder such as 4350, RL19, H4831? Post the data (group size and velocity) and we'll graph them out to see where accuracy goes south (exceeds the RPM Threshold) with each. Then we'll pick a load below the found RPM Threshold with each powder and a load above the RPM threshold. You can then shoot 10 shots with each at 100, 200 and 300 yards to find out if the group dispersion is linear or non linear. That should definitely show us something, ya think?

So there's your big chance frnkeore, to show us I'm wrong and to show us you can really do something other than quote someone else's work.

Larry Gibson

[MBTcustom]

Well Larry, regardless of whether Frank takes you up on your challenge, I'm going to. I have a nice Mauser with a nice 10 twist barrel, and enough five shot loads to incrementally work right over the proposed RPMTH, and if it's not raining Sunday (I'm praying) I'll be doing a little testing with medium burn rate powder. I may haul my press to the range with me along with some fast and slow burn powders.
If that happens, I'll post some pictures here with your permission.

And no Frank, I wasn't talking about you in my previous post.
What do you say? Wanna burn some powder with me?

[btroj]

A gain twist is intriguing but I wonder how it will do with cast. Will the changing angle of the lands cause leading? Will a good seal be easily maintained along an ever changing landscape?

I don't know.

[dtknowles]

A gain twist is intriguing but I wonder how it will do with cast. Will the changing angle of the lands cause leading? Will a good seal be easily maintained along an ever changing landscape?

I don't know.

I have asked myself the same questions and have not convinced myself that I could guess how it would work for better or worse. I think that since the radius of curvature is decreasing (getting tighter) so that should work to cut-off blow-by but it means the lead is being continuously worked the whole trip down the barrel. Only testing would tell.

Tim

[swheeler]

Brad maybe you can settle this once and for all when your new toy arrives. Seems like Gears rifle had the same twist as yours, 1 in 12 IIRC and remember reading a post by him where he hit a "wall" right at 2400 fps. Hum that's about 144000 rpms, wonder what happened? I will stay tuned for your test results before I make any decisions of my own

[Dutch4122]

Last night after Mike called me and asked me to get on this thread and post the results achieved thus far with my 03A3 Springfield I took a few hours to mull it over. Problems I had with even posting the information came from the fact that I knew there would be backlash. Not a huge deal.

However, it was not my intention to muddle up Larry's thread with my initial results obtained with a different type of alloy than he is working with in his testing. Notice that I mentioned in my post that this load needs more testing to see if it will stand up on paper. I also did add in to my post that I was using a different alloy than Larry.

My only intention was to help a fellow member who asked about the load that Mike mentioned. In hindsight, it would have been a better idea to PM dtknowles and give him the information that way or start another thread. Instead, the good old Cast Boolits thread drift that we are famous for has reared it's ugly head again. Not to mention the inevitable arguing over the distraction that drags the whole thing into the mud.

Larry and Tim do make a valid point. My post was off topic and could be counterproductive to Larry's testing.

Good luck with your discussion.

[swheeler]

Thread drift, NAW! I wouldn't do it on purpose and don't think you would either, it just happens.

[Larry Gibson]

A gain twist is intriguing but I wonder how it will do with cast. Will the changing angle of the lands cause leading? Will a good seal be easily maintained along an ever changing landscape?

I don't know.

Those are excellent questions. In addition would the changing angle add to the damage/imbalance done to the bullet?

Larry Gibson

[onceabull]

Dutch4122: Thread drift or not,I found enough value in your post to say THANKS..But,this being Cast Boolits,there has to be a ?... At the stated BHN of 28, is there anything available by actual testing,than shows some advantage to a copper enhanced alloy Vs.straight Linotype ??? Onceabull

[frnkeore]

frnkeore

No, it wasn't you. But to our previous discussion here's what you actually said; "A quick little reply lary and then I am acually done with it!" (where's the spelling Nazi's when you need them) I took it to mean you didn't want to chat with me anymore.....apparently you do?

Well if so then to the point; You just don't get it do you? This thread is about pushing a ternary alloyed cast bullet to as high a velocity as possible while maintain a certain level of accuracy (2 moa or less). All of your quoting of CBS match results tells us nothing we don't already know; yes you can push the RPM threshold to 160,000 RPM quite successfully. We've been doing that for some time. The point of the CBA matches is accuracy only; they don't care what the velocity is. Velocity with accuracy (not match winning accuracy but accuracy) is our purpose/goal here. What part of that don't you understand?

The idea is to push to as high a velocity as possible regardless of the twist. If you'll bother to go back a few posts and look close at the 2620 fps groups you'll see what the goal is. While we appreciate your love for CBA match results that level of accuracy at that low of velocity is not the goal here. Get it?

Now you apparently have an interest, an ability and some equipment. So why not do something constructive for a change? I believe you have a M98 in 8x57 and a very good Loverin mould? Why don't you give us ten 10 shot groups shot at 100 yards covering 1600 fps to 2400 fps with; a faster burning powder such as 4227, 2400 or even H110 and a medium burning powder such as 3031, 4895, 4064 and with a slower burning powder such as 4350, RL19, H4831? Post the data (group size and velocity) and we'll graph them out to see where accuracy goes south (exceeds the RPM Threshold) with each. Then we'll pick a load below the found RPM Threshold with each powder and a load above the RPM threshold. You can then shoot 10 shots with each at 100, 200 and 300 yards to find out if the group dispersion is linear or non linear. That should definitely show us something, ya think?

So there's your big chance frnkeore, to show us I'm wrong and to show us you can really do something other than quote someone else's work.

Larry Gibson

larry says:

Well if so then to the point; You just don't get it do you? This thread is about pushing a ternary alloyed cast bullet to as high a velocity as possible while maintain a certain level of accuracy (2 moa or less). All of your quoting of CBS match results tells us nothing we don't already know; yes you can push the RPM threshold to 160,000 RPM quite successfully. We've been doing that for some time. The point of the CBA matches is accuracy only; they don't care what the velocity is. Velocity with accuracy (not match winning accuracy but accuracy) is our purpose/goal here. What part of that don't you understand?

This is actually the title of this thread:

"RPM Threshold; A Tale of Three Twists, Chapter II"

Nothing about velocity. I think you need to open another thread about velocity if that is what you want to talk about. They are two different things.

With what we have learned in this thread, do you at least concede that YOUR "threshold" is actually somewhere between 160,000 and 190,000 RPM and not 120,000 to 140,000 RPM or, can larry, never say that he was mistaken?

"A quick little reply lary and then I am acually done with it!" I took it to mean you didn't want to chat with me anymore.....apparently you do?

I did say that, it was in reference to THAT thread and that thread only. The reason that I said it that way is because, you've said that you where "done with it" in that thread and many threads that we have had discussions in but, you have NEVER kept your word when you have said it. I didn't repost in that thread. I guess you call it "being a man of your word".

Dinner time, more to follow.

Frank

[Larry Gibson]

btroj

yes Larry, that Dutch did DOES prove something. I mentioned the need for hundreds of groups as you mentioned. Did you fire those hundreds of groups with each rifle? Did you vary anything? what makes your testing any more valid than what Dutch did?

Have you not really read chapters 1 & 2? Have you not read any of the reports I've made in other threads on this topic on all the groups I've fired, different bullets used (311299, 311334, 311284, 311291 (2 different moulds), 311041 (2 different moulds), MP 30-180-FN, 311466 (2 different moulds), 311465 (2 different moulds), 30-150-FN, C312-155-2R, LBT 30-160, 311359, 311413), different powders used (4895, Varget, 4064, RL19, AA4350, IMR4350, H4831, RL22, AA3100), different primers used (WLRs, CCI 200s, Rem 9 1/2s and Fed 210s), different GCs used (Hornady, Lyman (new and old), Blammer's and my own aluminum and brass and different lubes (Javelina, Tamarack, Lars 50/50, 2500+, LBT Blue, LBT Blue soft, Carnauba Red, RCBS rifle, 3 different Lyman lubes and a couple others I don't recall off the top of my head. I have tested all the variables mentioned including different bullets sizings (.308, .309, .310, .311, .312 and even .314) and several different alloys (6 to be exact). No I did not fire all those with each rifle because as you indicate the task to do that is daunting to say the least. What I found was what worked in one rifle the best most often worked the best in all 3 rifles. Yes some favored one a little more than the other but there was no set pattern as to which rifle. Conversely I found if one item worked poorly in one rifle it also worked poorly in all three rifles. As I narrowed down the variables to what was working I also narrowed the test to one rifle and then used what worked in it. As my objective was to push a ternary alloyed naked cast bullet to as high a velocity as possible with accuracy I focused on the 14" twist Palma rifle because the 10 and 12" twist rifles could not push velocities and hold accuracy to the level it could.

Now as to yours and a couple others continuing comment about the "different barrels". Understand this; 3 different twists were required. Ergo no matter if the barrels were from the same maker of the same make of steel or had the same contour the important part to the test, the interior of the barrel i.e the bore, would be different. This is because the twist is different so the cutter, the button or the mandrel that the grooves were made with would be different. Your continuing complaint that they are "different" is a moot point because they have to be different if we are going to have 3 different twists (note the adjective "different"). The scientific methodology for testing such is to use comparative analysis. In this case we simply compare a loss or increase in accuracy of a particular barrel to itself since the point of interests is simply that point (velocity and RPM) at which accuracy begins to degrade for each barrel. That 12" twist M70 Target rifle is more accurate than the 14" twist Palma rifle yet the Palma rifle shoots more accurately at a higher velocity with cast bullets. Yes they are "different". Different barrels or not; show me your 10" twist or even your 12" twist barreled rifle that is shooting with the same accuracy at 2620 fps as the 14" twist barreled rifle is with naked cast bullets of a ternary alloy. You can't, I can't and no one else has. The reason is because there is a difference; guess what that difference is?

Everyone except you and a couple others understand that. You will begin to understand it as you begin to push velocities up in the rifle goodsteel is building for you. You spent a whole long post outlining almost the exact testing methodology you need to use that I have been using for the last, what(?) 6 or 7 years in my own testing? And then you say you don't like my methodology.....that's the pot calling the kettle black isn't it?

Larry Gibson

[Larry Gibson]

larry says:


This is actually the title of this thread:

"RPM Threshold; A Tale of Three Twists, Chapter II"

Nothing about velocity. I think you need to open another thread about velocity if that is what you want to talk about. They are two different things..........Frank

I suggest you go to post #1 of this thread ("RPM Threshold; A Tale of Three Twists, Chapter II" which the "II" means it's a new chapter with a new direction) and read the 2nd paragraph which states; "My testing and load development then took the turn to see just how fast I could push a regular cast bullet of a ternary alloy with the 14” twist Palma rifle and maintain accuracy of 2 moa or less and maintaining linear group dispersion out to aminimum of 300 yards. "

Apparently with this being a gun related shooting forum you don't understand what "how fast I could push " means..........so apparently what you think isn't correct?

Since you don't understand that the rest of your post isn't worth responding to, especially since you fail to respond to whether you are going to do the test I suggested and that goodsteel is willing to participate in. If not it is obvious your intent is simply to criticize me and interrupt this thread with your nonsense. Do us all a favor and contribute something useful for once.

Larry Gibson

[Dutch4122]

Dutch4122: Thread drift or not,I found enough value in your post to say THANKS..But,this being Cast Boolits,there has to be a ?... At the stated BHN of 28, is there anything available by actual testing,than shows some advantage to a copper enhanced alloy Vs.straight Linotype ??? Onceabull

Question answered by PM.

[frnkeore]

Well, larry, I do think your intent for this thread was to see how RPM affected your ACCURACY with 3 different rifles, with 3 different twist and not just how fast your 14 twist would go. Am I wrong? What does the "tale of 3 twist" mean? The way I read this thread is that you were proving that RPM was the reason that accuracy fell off as velocity increased. Am I wrong again?

I would like to ask you again:

With what we have learned in this thread, do you at least concede that YOUR "threshold" is actually somewhere between 160,000 and 190,000 RPM and not 120,000 to 140,000 RPM or, can larry, never say that he was mistaken?

Frank