RPM Test; a tale of three twists, Chapter 2

[Tiger]

Larry

You said: The evidence so far still clearly points to RPM. Remember; same pressure, same velocity, (both of which evens out any difference in "rotational friction") much larger proportional change in accuracy with the 10" twist vs the 12 and 14" twist. The 12" twist also has a proportionally lager change in accuracy than the 14" twist. The only difference between them is RPM. Regardless of the straws we try to grasp the evidence so far is pointing in one direction only, RPM.


To that I say that this is what you say, not all of us. You are the great Albert Einstein, everyone has to prove him wrong. Is this a plan of yours having other find the real reason why there is a difference between rifling twists at higher rpm/velocity?

Yes I have shot the many different bullets out of the faster 22 bores. If I didn't have the rifle I was fortunate enough to have friends that did. We did not come to the same conclusion as have you. What I have found about the tags in bullet boxes is that most have a velocity limitation not a rifling twist limitation. Before you reply to that let me say that does not include the twist limitation because of the heavy weight for bore such as the newer 22 caliber bullets that require the 7, 8, and 9 rifling twists. That is why I found runfiverun's post interesting.

I have thought about Bass's deep rifling twist ideas. I have gone back through old post material and one that caught my attention was when there was much posting about the M95 Steyr 8x56R. It was mentioned in those old post about how deep the rifling is in that rifle. As I recall some of the members were were getting very decent shooting with this caliber and Bass mentioned the deeper rifling in that caliber. I like to agree with him in that area.

Ralf

[leftiye]

Bass, The bell isn't allowed to go ding (broked?). Tiger " You are the great Albert Einstein, everyone has to prove him wrong." Can't be done, not allowed.

[Tiger]

Larry

I make a statement and like a politician you attack it or misconstrue it into something else. I was pointing out with the jet plane that air creates friction which in turn creates heats, lots of it. Just one attempt at saying rpm isn't the animal responsible for jacketed bullet destruction at exceptionally high velocities. It's also not totally a thin bullet jacket either. Many times it can be if the jacket alloy is tough enough to with stand the rifling stresses put on it alone the friction through the air.

That brings up the golf ball again. You just keep on repeating what you have to say about the spin. Let's try this. If you touch a spinning gyroscope what happens? Does nothing happen? I think not. Air does have mass. The centrifugal force of the bullet spinning does have a reaction against the air it is cutting through. What happens to a bullet when it's cutting through animal flesh? Besides the mushrooming or other physical destruction? In many cases it tumbles. Why?

I believe I'm with Bass and others here that most the inaccuracy damage i done to the bullet while still in the barrel.

Ralf

[mainiac]

Havent been on this site very much lately, but am now reading this thread with intrest. If you read back in the history,you will find a thread about my 22 hornet. Up to 2900 with fair accuracy(2600 very accurate) with ACWW. Shoot lyno boolits in this gun and it shoots 15 inch groups,at best!!! Seems boolit hardness aint the answer.BTW, boolit was the 225415 checked,with felix lube. And on to my current head scratcher,,,,,,,,,,,, snows finally melting away up here in the north, today i was shooting and noticed the lead on the ground from my swinging gong target. Have wondered this before,, 70-75% of the lead is ALWAYS spattered off to the left side of the target. It isnt a angle thing,im sure. This has to be a twist thing! Almost all barrells are rifled right hand, and im thinking the direction of the twist makes the boolits shatter left. If I could only get ahold of a left twisted barrell, I would find out! Anybody have any thoughts?

[Tiger]

Havent been on this site very much lately, but am now reading this thread with intrest. If you read back in the history,you will find a thread about my 22 hornet. Up to 2900 with fair accuracy(2600 very accurate) with ACWW. Shoot lyno boolits in this gun and it shoots 15 inch groups,at best!!! Seems boolit hardness aint the answer.BTW, boolit was the 225415 checked,with felix lube. And on to my current head scratcher,,,,,,,,,,,, snows finally melting away up here in the north, today i was shooting and noticed the lead on the ground from my swinging gong target. Have wondered this before,, 70-75% of the lead is ALWAYS spattered off to the left side of the target. It isnt a angle thing,im sure. This has to be a twist thing! Almost all barrells are rifled right hand, and im thinking the direction of the twist makes the boolits shatter left. If I could only get ahold of a left twisted barrell, I would find out! Anybody have any thoughts?

Mainiac

That's good shooting with lead for a 22 Hornet. I will try to explain this before Larry Gibson runs it down. Most Hornets have a rifling twist of 16.
So with that piece of data plugged into the rpm formula along with the 2900 fps, Larry will say that the resulting 130,500 rpm is well within his rpm range limits.

I too have found that linotype doesn't always solve a cast bullet problem but presents more. Notice I said doesn't always. The other times it performed well.

Ralf

[leftiye]

Manic 1, Sometimes the boolit fit isn't quite right, and the boolit has to obturate (get KITA like a muzzleloader boolit does when it bumps up to groove diameter). Sometimes softer lead will continue to do this as it travels down the barrel, and makes up for barrel irregularities or roughness, and damage to the boolit. A hard boolit can't do that. Is it possible that the lino boolit was undersized? Your post on the Hornet warms my heart. I am working on getting one or more Hornets going right now and it helps me to hope for good results.

[Pat I.]

Larry, since the attacks are getting personal and the opposing ideas and helpful hints are a little strange at times why don't you just finish your tests and post or publish the results. That way people can make up their own mind if they believe cast bullets are twist limited for attaining best accuracy. Personally I believe they are but that's unimportant to the conversation or you're testing.

[sundog]

Larry, I did not read back through all the posts in this thread. I did want to convey some info to you though. At the behest of my good buddy, Felix, I loaded some AC WW/RS 314299, sized .312, over 28 and 30 surp 4895 for a heavy bbl .308. That samest batch of boolits shoot extremely well in a custom Mdl 70 with 10 twist. The 28 gr load shot lights out in a heavy wind quartering from the right front, wind NE, shooting N. At 100 yds 9 rounds took out the Xring and the 10th was a very solid 10 at 5 o'clock which was more my fault than anything.

The next 10 rounds were the 30/4895, same boolits, and they made a 4 inch wide group across the top of the black (SR21) with a single round an 8 at 8 o'clock, which again, I suspect was my doing.

So, from 28 to 30, something happened. It wasn't me (I've been shooting long enough to know), and it wasn't the conditions. No chrono. I suspect the 28 grain load at about 1800 - sure was a pretty target.

I shot from this same batch of boolits for the mil bolt match. I shot smallest group of the day with 03A3 @ 1.999 and came in second overall score with a 288/300 and Xs. Did I mention that it was windy? At least 15 G 30 @ 315 (NE) shooting 360 (N). And it was about 40dF at shoot time.

So, what do we suppose about those loads in the .308 with a 12 twist?

[Larry Gibson]

Mainiac

That's good shooting with lead for a 22 Hornet. I will try to explain this before Larry Gibson runs it down. Most Hornets have a rifling twist of 16.
So with that piece of data plugged into the rpm formula along with the 2900 fps, Larry will say that the resulting 130,500 rpm is well within his rpm range limits.

I too have found that linotype doesn't always solve a cast bullet problem but presents more. Notice I said doesn't always. The other times it performed well.

Ralf

Thanks Ralf, you're all over it.

Larry Gibson

[Larry Gibson]

Larry, since the attacks are getting personal and the opposing ideas and helpful hints are a little strange at times why don't you just finish your tests and post or publish the results. That way people can make up their own mind if they believe cast bullets are twist limited for attaining best accuracy. Personally I believe they are but that's unimportant to the conversation or you're testing.

Pat

Like I said; I don't know why I'm still in this converstation. On to the tests. Thanks.

Larry Gibson

[Larry Gibson]

So, what do we suppose about those loads in the .308 with a 12 twist?

ACWWs is a pretty soft alloy these days. Without knowing the velocity I'd say you were in the low end of the RPM threshold with the 30 gr load of 4895. The 28 gr load was accurate, the 30 gr load was not. The 28 gr load was slightly in or below the RPM threshold. The 30 gr load probably exceeded the RPM threshold for that bullet of that alloy in that twist. Would be nice if you would use a chronograph when testing loads as there could in fact be other reasons for the inaccuracy also. Note the example of the inconsistant ignition with the 14" twist during the test I ran. Hard to say exactly without facts. The chronograph would have given us some facts.

Larry Gibson

[Tiger]

ACWWs is a pretty soft alloy these days. Without knowing the velocity I'd say you were in the low end of the RPM threshold with the 30 gr load of 4895. The 28 gr load was accurate, the 30 gr load was not. The 28 gr load was slightly in or below the RPM threshold. The 30 gr load probably exceeded the RPM threshold for that bullet of that alloy in that twist. Would be nice if you would use a chronograph when testing loads as there could in fact be other reasons for the inaccuracy also. Note the example of the inconsistant ignition with the 14" twist during the test I ran. Hard to say exactly without facts. The chronograph would have given us some facts.

Larry Gibson

Larry,

What do you think the velocity, a guess, is of Sundogs 30 grain load? I looked in the Lyman Cast book and they didn't list that exact bullet but the heaviest one listed using a 311334 and a paper patch bullet 301620 did have 4895 loads. First bullet gave 1879 fps to 2497 fps with 28.3 grainds to 40.8 and the second bullet gave 1673 fps to 2427 fps with 23.8 to 38.4 grains of 4895. So to hazard a guess being Sundog is using a faster twist and heavier bullet making his bullet slower then what is listed here, I'd say his 30 grain load was going not much over 1900 fps. If so that gives us 136800 rpm. I do not consider this such a high rpm. Please don't tell me for his alloy, bullet, load, rifling, etc., that this was the limit. With a change in velocity there is a change in many other things, barrel harmonics to name one. Out of hundreds of variables you for some reason selected rpm. I and others disagree. How will your test prove 100 percent that rpm is the accuracy killer?

Ralf

[runfiverun]

with the 30 gr load he was also at about 32000 psi.

[Tiger]

Run

I'm glad that you brought that up. I was just going to post about using different burn rate powders. Say you take four suitable powders with different burn rates and keep assembling and shooting loads until you get loads with all four powders that read the exact same velocity on your chronograph. Ok, my question to all of you is WILL THE ACCURACY BE THE SAME FOR ALL FOUR POWDER LOADINGS? If you say no then that leaves rpm out of the story.

Ralf

[runfiverun]

tiger my first reaction here was no
but ,
if those powders were i4895 h4895 aa2498 i would say yep
if they were 322, 4895 rl-19, h1000
i would say i don't know .

i know what you are saying here internally every thing has more to do
with accuracy.
but whats happening in the bbl is affected by rpm's, as well as what happens
out side of it.

rpm works on the boolit longer than the internals do.
if you were going to build a rifle and was going to use it for cast shooting
would you want the one that is the easiest on it?

i dont see how assembling loads to a certain velocity would leave the rpms out of
the equation.

oh and this is how i start a lot of my load development,anyway.
guess thats why i use 322 in one gun and 4895 in another.
i targeted velocity then worked it around till i was happy with it.

[Larry Gibson]

Ralf

Sundog did not say whether his rifle was a 10 or 12" twist. Since he asked; "what do we suppose about those loads in the .308 with a 12 twist?", I answered as if he was talking about his rifle having a 12" twist. That being the case and the fact that Sundog gave little information about his barrel I hesitate to guess at the velocity. My answered was predicated on the fact that the 28 gr load was accurate and a 2 gr increase to 38 gr load was not accurate. That usually is indicative of the bullets RPM exceeding its threshold. Excuse me but I do not buy off on the "harmonics" gambit. A good heavy barrel that is accurate will continue to be accurate. If there is inaccuracy then there is another reason and it is not harmonics.

"How will your test prove 100 percent that rpm is the accuracy killer? "

Read how the test is conducted. Read the results of the first test as reported in Chapter 2. Perhaps you will then understand that I did not "select" RPM. The test results are demonstrating very clearly that it is indeed RPM.

Larry Gibson

[Tiger]

None the less Larry, the question I asked still stands. Will the accuracy of the four different burn rate powders be on the same level if all have the same velocity? I don't think so, in fact I know they will not. It's not rpm Larry.

Ralf

[Tiger]

None the less Larry, the question I asked still stands. Will the accuracy of the four different burn rate powders be on the same level if all have the same velocity? I don't think so, in fact I know they will not. It's not rpm Larry.

Let me restate that, it's not rpm outside the barrel.

Ralf

[Tiger]

Sorry about that double post as I was trying to edit the one.

Runfiverun I'm not saying that rpm has nothing what so ever to do with the accuracy, I'm saying the damage, if any is occurring, is happening in the barrel. Then of course rpm will amplify that damage outside the barrel. The different versions of 4895 are so close to one another I don't think there would be a difference either, but I did say four powders with different burn rates meaning entirely different burn rates, which you did answer too.

So why do you think with the four different burn rate powders the accuracy would be different? Will you tell me because of the different pressure applied to the bullets?

Ralf

[sundog]

12 twist hvy bbl Rem 700 VS. I have some WQ WW/RS 314299 that I'll repeat the test with as soon as the wind dies down a bit around here.