I’ve been following this thread with interest...a lot of good information in it. Wasn’t really planning on weighing in on it, because as it initially began, viewed it as an excellent well-documented experiment on Larry’s part. Really felt I had nothing of value to add. Still don't. However, sometimes feel the need to express an opinion even though common sense tells me it would be better to keep my mouth shut. This is one of them:
Have to give Larry a lot of credit for doing this test, the manner in which he performed it, and for taking the time to present that information to us...then taking the time to defend it.
That’s really how science should operate. You have a theory so conduct a test to try to validate that theory. Then subject it to a critical peer review. Usually, that review will involve much criticism if it flies in the fact of currently accepted fact. That’s what happened here. Larry stated the conditions under which he performed the test and his results...and a fine and thorough job he did with it. Problem began when he stated his conclusion of an RPM threshold. I don’t see how any fair minded person can argue with his test...or the fact that for his .30 caliber rifles and bullets, he established a definite relationship between bullet RPM and accuracy...which in turn defined an ideal upper velocity limit based on the twist for those rifles.. Now you can argue why that RPM threshold existed, whether it would apply to other rifles with different lands, different barrel lengths, powders etc. or whether revolutions per distance rather than RPM should be looked at also. However, those remain just interesting distractions (doesn’t mean they aren’t worthy of discussion in their own right). It seems to me that Larry accomplished what he set out to do . If one wishes to truly refute Larry on this issue, you’d have to set up a like experiment, post the results to refute it, and accept your own peer review. Until then, the facts as provided by Larry, back him up.
I can do what I want to with those test results...but can't argue with the facts themselves. I can argue why RPM should have an upper limit for his accuracy, if it would apply to other calibers, if it is a hard and fast rule, what other variables could be involved, etc. However, based on his test and for his conditions, he proved an RPM threshold to me. Seems to me it may be a good “rule of thumb” for a “run of the mill” caster to follow on a .30 caliber. I’m not willing to translate that to other calibers at this time due to the different rotational energies involved ...however, with his data in hand I could use that.30 to establish a theoretical value for them as well by assuming a direct relationship to energy involved. That assumption may or may not be true and require further experimentation...but Larry’s information, whether true or not for other calibers, still offers a starting point. I have no doubts that someone with expertise and time for experimentation could push that .30 caliber envelope up...just the way it works. Where casting is concerned, there are too many variables to make hard and fast rules...just good “rules of thumb” which will work in the vast majority of cases. IMO, unless someone can refute Larry's theory with a documented test providing hard facts, Larry has done just that.
My background is math and physics. I understand physics and mathematics which has appeared here. Physics really comes into play in trying to do an in depth study of this casting and shooting sport of ours. However, it’s so complex in that we also need knowledge of chemistry (primer, powders, lubricants), metallurgy (barrels and bullets), and engineering (bullet and firearm construction) among others to begin to approach a complete scientific look at it. Even then, one would still have a real problem in applying pure science to the issue in that one couldn’t measure initial conditions accurately enough (center of mass of each bullet, energy equivalency of each powder charge, case tension...on and one) , ...or the actual forces and dynamics involved once that trigger is pulled (barrel harmonics, pressure curve, bullet friction, acceleration, associated bullet deformation, etc.) . The list of what we’re guessing or assuming is pretty large. As a result, theoretical implications are open to dispute. All we have is empirical evidence...such as Larry provided.
I am grateful to anyone who is willing to conduct research and provide their results and conclusions. Even if one disagrees with a conclusion, the research remains valuable in and of itself. Review the data, draw your own conclusions if you wish, debate them if you must , but please don't let those honest debates degrade to personal attacks. When it becomes personal, only the “thick skinned” will publish their study or voice an opinion...and we will all become poorer for it.
Kudos to Larry for his work!