RPM Testing the 311291

[Bass Ackward]

People are too worried about the election, so I decided to get your mind off of it for awhile. I finished shooting the 311291 belonging to Larry Gibson after educating myself in many way as to why. Here are some of my findings.

The nose portion of this bullet did not fit any of my 06s at .298 using my mix, so I stayed with my 700 Remington with 36X scope for all shooting. The control load for my low velocity to HV testing was 16 grains of 2400 often quoted as the universal load. With this load, the average for three, 5 shot groups was 2 1/8”. So that was my low velocity accuracy standard that had to be beaten. I was supposed to beat it over 140,000 RPM. The poor low velocity accuracy standard was what it was and not investigated just accepted for what it was.

During summer testing, I was was not able to match or beat it. Every load I tried was way over the pressure / velocity that Quickload predicted and it clearly looked like I had an RPM effect. Lube change didn’t matter, hardness didn’t matter. First three shots might be less than MOA, but the last two would put me either slightly above or way above the accuracy standard. Only one powder showed even this promise do the job which was Accurate 3100. Then I could hold 3, 5 shot groups at 2” using 49 grains if I let the barrel cool. This was 2100 fps or 151,000, but groups got worse the more they were shot.

Cooler weather has made a difference. And actually now 52 grains is now the accuracy point at 2300 fps or 165,000 with the same hardness and lube. Three, 5 shot groups now will average 1 ¾” which is less than the low velocity accuracy standard, but not by much. And I still have to let the barrel cool between shots. Quickload says 30,000 psi is maximum for lead in this weight and design unless it gets cooler or I get taller rifling. This design is clearly not for this rifle. But why so poor?

I took some 180 Speer round nose bullets I had left with the same load. Accuracy was about 2” for the first 5 shot group at 2250 fps. They opened with each group after that to about 2 ½” with the 3rd group averaging 2350 fps as copper altered bore condition and was raising pressure. The jacketed handled the fouling, so it lead me to believe my bedding would have to be altered to get this velocity range tuned in much better than it was. My harmonics was clearly off for this accuracy point.

[Bass Ackward]

So why won’t “this” 311291 work at HV?

I did some measuring. The nose of this design doesn’t fit or make contact, at .298 so that rest of the bullet must hold bore center to work. The bearing length of this design is .600 of a .980 length bullet. That’s only .62% of available weight to contribute to holding bore center and countering rotational forces as they increased with velocity. If the nose tips, the base follows and it is now longer perpendicular with the bore or the crown. So everything needs to be right here. Is it? Why won’t this shoot better?

The group size difference with the temperature change had me investigate. I used a .308 Lee sizer as this is my bore measurement. A single bullet was used. It was molded, weighed, lubed to the hilt without sizing, then sized to bore diameter as a rifle barrel would do minus the rifling displacement that would reduce lube capacity even farther.

Bullet weight:

Naked: 171.1 grains.
GC: 4.3 grains
Lubed w check: 175.8 grains
Sized to .308: 175.6 grains

So this bullet is carrying only .2 grain of lube. No wonder why changing lube or hardness made very little difference. And the rifling engraving would have occupied even more of the lube carrying space, so this design is only going to have minimal amount of lube to work. When that lube is used up, it’s gone. Pressure is going to raise and if you are operating right on the edge already, then you are going over what the slug can handle and accuracy will get worse. The faster you go, the more fouling you leave and the more fouling must be passed. So the more out of balance the bullet gets and out of square square the base becomes. Accuracy will get worse as you go on up. An RPM effect? Clearly, the best operating range for this slug is the point where it first stabilizes and that’s it. Can this design help itself?

[Bass Ackward]

Can it help itself?

I measured the GC groove at this diameter and the gap to remove fouling was only .017. A human hair measures .015. Clearly, the lack of lube was going to leave fouling, but the GC groove was not going to be capable of handling very much before it loaded up. This explained why my groups opened with the number of rounds fired. Meaning that once fouling was left, the next bullet was going to have to iron it on in order to pass it. Just as the jacketed Speers did above. This is going to raise pressure and velocity.

Once the bullet passed, the bullet would be sized down by how ever much it had to to pass this fouling as it built up and no longer contributing to the rotational effort or holding bore center. Same thing as lowering rifling height and unbalancing the bullet at the same time.

So clearly what we have here is a bullet design that as it speeds up can not either prevent or clean up it’s mess. Sort of explains why some of the early bore ride designs had a clean out groove in front of the front band. But lead is only so strong and the best fouling is that which is not left behind in the first place.

Why is the 311291 limited in it’s velocity or accuracy capability?

1. Did not fit well enough that the nose could help it could hold bore center.
2. Not enough bearing area to handle rotational forces as the RPMs increased.
2. Doesn’t carry enough lube to prevent fouling.
4. GC can’t clean up it’s own mess when it does.

So should we draw conclusions from a single design cherry? No, maybe another 311291 cherry might be better. But bullet design can be strengthened considerably so that it doesn’t have to be as hard. Or carry as much lube. Or can be shot faster without fouling. Well, you get the idea. Fit adds strength, but strength of design is better.

Better than the election huh?

[Larry Gibson]

Bass

How cold is "colder weather"? It was 60 degrees here when I ran that bullet through my '06 with 3100 powder. I got no where near that accuracy at that velocity with it. I did however get right at 1" five shot groups with the same 311291 using 4895. I also got 1.75 - 2.25" five shot groups with RL19 and H4831SC at 2300-2400 fps. However, you seem to forget my RPM Threshold test was mostly with ten shot groups. No difference though as we both achieved essentially the same accuracy give 5 shot groups. This was during the continued (after all the hullabalou and I quit posting the results of my continuing RPM tests due to the obnoxious posts of a few) continued and completion of my test. No I will not post the final results test here, just examples now and then as I am now. Perhaps my rifle just doesn't like 3100. Perhaps your rifle just doesn't like 2400. I'd suggest you try working up a low velocity accuracy load instead of just accepting a "universal load" as the best it can do. Makes for a more structured and scientific test that way.

Another couple questions; how much lube does your LBT bullet carry (I already know the answer)? So why doesn't it "run out of lube" with less lube at the same velocity?

However, my point here is to thank you for your tests and conclusions. They once again demonstrate how all the defects of design and all of the things that happen during accelleration (internal ballistics) to a cast bullet. Thus when the cast bullet leaves the barrel the adverse effect of RPM takes over at a certain level with the accuracy deteriorating. This is the RPM threshold. The accuracy may or may not deteriorate a lot. That depends on the things we do in preparing and assembling the load. I do believe we have both stated that numerous times since this RPM threshold discussion began.

One last point; my '06 only has a 9X scope on it, advantage Bass. Just kidding here Bass, I shoot quite well with it even though I'm so "low powered".

Larry Gibson

[45 2.1]

I'd suggest you try working up a low velocity accuracy load instead of just accepting a "universal load" as the best it can do. Makes for a more structured and scientific test that way. Larry Gibson

The same exact thing was suggested to you also and you refused. My my, time and perspective does change things.

[Larry Gibson]

45 2.1

Can't you come up with something new?

The fact is I did work up numerous loads in the RPM threshold test from a low velocity of 1800 fps up through 2800 fps using;

3 different .308W rifles with 3 different twists - 10, 12 and 14"
2 different 30-06 rifles with 10" twists
5 different powders
5 different primers
3 different GCs
6 different lubes
3 different neck tensions
3 different bullets
3 different alloy hardness
6 different bullet sizings
I also measured about everything that can be measured using an Oehler M43 PBL. (if you forgot what all the measurements were refer to my first RPM threshold post and read it)

Just what exactly have you done (like Bass and I) to prove or disprove the RPM threshold besides flap your jaws?

I also accomplished the exact same thing that Bass has. Had you simply waited for the test to be completed and all the results of the test to be posted you would know that. However you chose to argue and second guess everything beforel the test was even completed. If you could even recall (that is if you even really read it) the first post on the RPM threshold test you'd remember I said i was going to also see what could be done with the 311291 in the '06. I did exactly that and achieved the same results as Bass.

Do you have a point other than to simply argue! This is the last I will discuss this issue with you unless you get reasonable and make a contribution backed by a test or can ask a reasonable question.

Larry Gibson

[45 2.1]

Indeed Larry, perspective does change things, now you have turned your results around without finishing your tests or publishing the results.

Larry wrote:I did exactly that and achieved the same results as Bass. Well, it doesn't appear that way. Bass got better groups at higher velocity past your so called RPM threshold and you didn't. All with the same mold, but different methods.


How Obama of you.

[Larry Gibson]

Folks

Apparently 45 2.1 can't read. I believe I distinctly said the RPM threshold test was finished (has been for a couple of months) and why I won't post the results. Inane posts like 45 2.1s is the prime reason. How inane? In one sentance he says I haven't "published the results" and in another sentence says I've "turned the results around". How does he know if I've not published the results? Inane indeed! I also distinctly said I got the same accuracy with 311291 at 23-2400 fps as Bass did except I did it with RL19 and H4831SC. Yet 45 2.1 says, "Well, it doesn't appear that way". Perhaps he can't read well because he needs glasses.

Many of you have PM'd me wanting me to post the results of the RPM test. You now see why I won't. The reason is simply because of the continual inane and rediculous responses it gets from 45 2.1 and a couple others.

I also find his "How Obama of you" to be totally dispicable and insulting to everyone on this forum.

Larry Gibson

[45nut]

I too find that offensive and wish the name calling would cease, now. There is no reason for it when discussing such topics.

[Bass Ackward]

However, my point here is to thank you for your tests and conclusions. They once again demonstrate how all the defects of design and all of the things that happen during acceleration (internal ballistics) to a cast bullet. Thus when the cast bullet leaves the barrel the adverse effect of RPM takes over at a certain level with the accuracy deteriorating. This is the RPM threshold. Larry Gibson

Larry,

Ah ......... sorry. That is not what my data showed. My testing explains yours and mine.

My groups were shot at 50 and 100. The 100 were double the 50 and not worse. That means that RPMS was NOT the cause of what ever accuracy or inaccuracy I got, nor was RPMs affecting me negatively at least to that distance.

You asked WHY you don't get the same results? You do, you just interpret it incorrectly.

Your slower twist rate damaged bullets less in your bore so your bullets held center better and broke seal squarely. This means that muzzle pressure caused less yaw in your slower twists and thus bullets stabilized sooner to travel straighter or more accurately. That's what your testing showed me. Slower twist has the the same result as a longer barrel. Better launch.

It's all about the launch. That's what I interpret from all of this at least to this point. And fouling and heat are the true enemy. Same with jacketed just amplified with cast cause it's softer and requires lube.

[Larry Gibson]

Bass

I beg to differ with you. Your testing only confirms mine. Call it a “launch” if you must but the fact remains that the adverse affect of RPM is what causes the inaccuracy of cast bullets above a certain level. My tests with the 3 different twists prove that. If you’ll recall I have always said the RPM threshold could be pushed. How far was the question? In the case of the 311291 we both agreed the way to go was with a larger case and slower burning powder so the bullet would be less damaged during acceleration. I stated in my RPM posts that at the end of the test with the 3 barrels in .308W I would also test 311291 in a 10” twist ’06. I did that and achieved good accuracy at 23-2400 fps with RL19 and H4831SC. You now have done the same thing only with 3100. So you see I don’t interpret anything incorrectly. You shoot sub 2” groups at 100 yards and I shoot sub 2” groups at 100 yards. Not too hard to figure out. However, for joe reloader who asks why can’t he shoot a 311291 “at velocity with accuracy” out of his ’06 the answer still remains; he isn’t going to. “At velocity” for a normal ’06 with 170-180 gr jacketed bullets is 2650-2700 fps. You and I have pushed the RPM threshold with 311291 to 23-2400 fps but neither of us have got the same accuracy at 26-27—fps, now have we? The reason is, though we have “pushed” the RPM threshold it will still bite us above where we are at.

Also, again note, my last tests and the ones I referred to in my post to you were shot with two different 30-06s with 10” twist barrels. The twist I used is the same as you were using. There was no difference between your “launch” or mine. But since you brought up the slower twist I might add that with the 14” twist .308W I have been getting fairly consistent ten shot 2” groups with 311466 at 25-2600 fps. On several of those groups the first 5 shots go into 1” or less.

Some still think the RPM threshold is a limit. It is not. I hope you are not still one of those. It can be pushed but only so far and only under the best of conditions. I’ve not been able to run a 10 shot string with accuracy under 2” with my loads without cleaning the barrel. I’ve tried the magic LBT and it doesn’t perform any better in this regard BTW. We accomplish a pretty nice trick with sub 2” groups at that velocity but it might not be too practical. Again to joe reloader who wants to shoot perhaps 40-50 rounds in and hour of two practice session isn’t going to achieve the same results we have. The reason he won’t is RPM.

Larry Gibson

[leftiye]

"However, for joe reloader who asks why can’t he shoot a 311291 “at velocity with accuracy” out of his ’06 the answer still remains; he isn’t going to." L.G.

I agree, he isn't going to. The reason being the faulty design of the boolit as marketed by Lyman and as outlined by Bass. RPMs only acts upon faults that exist in the boolit's situation as it leaves the barrel (you yourself have said this). If the design is correct, and the load is done so that no erratic yawing, imbalance, and etc. exist, then the whole RPM thing changes upward drastically - you've also said this yourself. Blame the causes, not the effects. Yes RPM does have an effect, but its effects are pursuant to defects found elsewhere and all that anyone can do about it lies elsewhere in removing those defects.

[Larry Gibson]

Leftiye

Congradulations, you've got it. BTW; the "effect" is inaccuracy. The "cause" is all that you say that I've said and RPM. As you say; no defects in the bullets then the RPM has nothing to "effect", adversely or otherwise. The problem is it is very hard to keep a cast bullet from deforming during the higher end accelleration required for higher velocities. In the .308W to get a 160+ gr bullet above 2500 fps is going to take 40,000+ psi. In the '06 you can get a 177 gr 311291 above 2500 fps with psi's in the mid to high 30,000 psi range. Small things like that begin to make a difference as Bass and i have mentioned in previous threads. Good to see we agree, on some things anyway

Larry Gibson

[Bass Ackward]

However, for joe reloader who asks why can’t he shoot a 311291 “at velocity with accuracy” out of his ’06 the answer still remains; he isn’t going to. “At velocity” for a normal ’06 with 170-180 gr jacketed bullets is 2650-2700 fps. You and I have pushed the RPM threshold with 311291 to 23-2400 fps but neither of us have got the same accuracy at 26-27—fps, now have we? The reason is, though we have “pushed” the RPM threshold it will still bite us above where we are at.

Larry Gibson

Wow. I thought this would be a good distraction and it has legs of it's own.

Larry,

This statement here is the foundation of our difference in opinion.

A cartridge has a pressure limit set by SAAMI. If take a look at all the jacketed bullet weights in any reloading manual for any caliber, the highest velocity will be obtained with the lightest bullet weight in every caliber. The key word there is pressure limit. It is uniform for all weights, but it still results in a lower velocity for heavier slugs

With cast, you have a different pressure limit. The limit is now set by lead and rate of pressure. It is a sliding scale and NOT a FIXED limit because of inertia. Factors there are bullet design and fit, weight (inertia) lube and bore condition.

As you go up in bullet weight, you create more inertia that will require a slower rate of pressure rise to reach the same velocity. But in the end, no matter what you do, no matter how much you try, the lightest weight cast bullet will always be able to be driven faster than the heaviest weight. Same logic, just a different "pressure" standard. (that we control)

If my success with a 154 grain bullet peaks and is 2500 / 2600 fps in the 30-06, then it is physically impossible to expect a 175 grain slug to approach that at anywhere near that level unless I can harden it or change any of the factors.

I listed the factors above that will permit a higher PRESSURE limit for the same hardness lead. Better fit, stronger design, more lube capacity or better lube and an ability to clean up after itself. Those 4 things are critical to a new reloader to understand .... WHY he is inaccurate. That is if you REALLY want to help him.

That will be lost if we simply tell him RPMs. Not only is it misleading, it's untrue. When the 311291 failed with heat in July and August, pressure ran up enormously. I was running 2600 fps loads and leading severely. That load was 13 1/4" at 100 yards with round holes. But it was 6 1/2" at 50 yards with slightly oblong holes. Here is the KEY: RPMs WAS HELPING me cause it hadn't fully stabilized it yet at that distance. What failed me was the yaw at the launch.

Bottom line, I was running maximum jacketed pressures and had " ZERO " RPM effect on accuracy. (to that distance of course cause velocity was high enough) 100% of inaccuracy was solely attributable to factors relating to pressure even with the slug WAY out of balance. Can't imagine it could possibly get any worse. Wasn't anything to recover at the back stop to verify my speculation. But it was RPMS that actually helped me get flight under control and stabilize.

So telling someone it's RPMs when RPMs doesn't always have something negative to do with it and it's really something else, just doesn't sit right with me. Fight the battle that needs fought. If you got an RPM issue because you bullet is out of balance, you actually need to INCREASE VELOCITY (rpms) to get the out of balance bullet to stabilize and it will remain stable until enough velocity is lost. It's EXACTLY the same with a handgun on the slow end. Then RPMs works negatively on the out of balance slug when your velocity drops back again.

But the REAL cause for inaccuracy was yaw caused by factors that directly come back to pressure resulting in a failed launch that went really bad. But what RPM you need to stabilize is all in the quality of the launch.

[Larry Gibson]

Bass

Please try telling me something I don't already know about pressures with jacketed and cast bullets. There is no difference in our opinion on that. You took several paragraphs to explain the same thing I said to leftiye in two sentences. We agree on what it takes to get accuracy at high velocity (the 4 critical things you reiterated).

Telling joe reloader that RPM is the reason for his inaccuracy is not misleading nor is it untrue. Fact is, it is true. What is misleading is to not tell him the reason. To just tell him to get another mould, change lube or try a slower powder does not help him understand the problem nor to help him get closer to where he wants to go. He wants to go there with 311291, the lube he is using and the powder, etc. If you don't tell him the reason all that won't get him there is because the bullet is damaged (unbalanced due to the initerial effects of setback during acclelleration) and the increased RPM is adversely affecting the accuracy above a certaian velocity then that is a diservice to joe reloader.

All this is a matter of opinion; mine vs yours I guess. Perhaps a matter of perspective on what we should tell joe reloader. Whatever we tell him does not alter the fact that there is an RPM threshold for regular cast bullets. As I've said repeatidly; that threshold is not a limit. It may be pushed by close attention and balance of the 4 critical things you and I have mentioned.

The fact that the RPM threshold can be pushed does not negate it's existance. This is why most eveyone here can and has loaded any regular cast bullet in a rifle cartridge in rifles with 12" or faster twists up to a certain velocity (most often that velocity is well below the reputed "pressure limit" for cast bullets) with very good and often remarkable accuracy. Then when they try to push that same bullet above that velocity level accuracy goes south. The answer and reason is RPM.

Larry Gibson

[carpetman]

Is Joe Reloader any kin to Joe the Plumber?

[Larry Gibson]

Bass

One last note; if you had enough yaw at "launch" to cause the 6 1/2 and 13+ inch groups then the problem was not one of RPM "helping you". It certainly stabilized your bullets. However, you seem to still think that the adverse effect of RPM is all about it making the bullet yaw and wobble to decrease accuracy. That isn't so. The adverse effect of RPM is all about the center of spin not coinciding with the center of form or the center of gravity. This effect, while adverse to accuracy, does not produce yaw or wobble. It means the bullet will begin a slow spiral off from it's intended path of flight. The holes through a target will still be round. The bullets bullets will fly point forward but just won't be spinning concentrically so to speak. The faster you spin the bullet the greater the spiral away from the intended path will be. This is called "inaccuracy". When you understand how that happens it will clear up a lot of misconceptions you still appear to have regarding the bullets flight. Had you shot your 2600 fps load that gave 13+ inch groups at 100 yards at 200 yards you would have see the non-linear effect that the RPM would have had. I ran that test for you, remember?

This has nothing to do with a bullet "going to sleep" so let's not get side tracked on that issue.

Larry Gibson

[Larry Gibson]

Carpetman

I believe Bass wanted to keep politics out of this...and reference to the election....hope everyone voted.

Larry gibson

[carpetman]

Maybe politics are needed here. Research at this high level and magnitude of importance may be worthy of some federal funding.

[Bass Ackward]

The fact that the RPM threshold can be pushed does not negate it's existance. This is why most eveyone here can and has loaded any regular cast bullet in a rifle cartridge in rifles with 12" or faster twists up to a certain velocity (most often that velocity is well below the reputed "pressure limit" for cast bullets) with very good and often remarkable accuracy. Then when they try to push that same bullet above that velocity level accuracy goes south. The answer and reason is RPM.

Larry Gibson

Then you have a problem. The laws of science don't stop because one has a certain quality rifle or passes a certain number. The RPM theory will have to be up and down the line.

When someone throws 16 grains of 2400 in an 06 with any factory mold and they shoot 2" when the guy next to him shoots the exact same thing and gets 1", then there is only one correct answer.

According to the RPM theory, he is shooting a better balanced bullet that allowed him to shoot more accurately than you.

Going to sound kinda stupid isn't it?

Even worse is going to be explaining why as a fella does a ladder and comes up with a load why accuracy goes south and then comes back. RPMs doesn't quite cover that one.