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Old March 31, 2012, 12:01 AM   #10
Bud Helms
Senior Member
 
Join Date: December 31, 1999
Location: Middle Georgia, USA
Posts: 13,198
I think what Bart is saying is not necessarily in opposition to any of your common sense assertions, John. He is simply saying that they do not necessarily always cause the results we have come to assume. Bart may disagree with that.

By the way, as an instrumentation technician at a USAF testing facility in FL, I was fortunate enough to see for myself the primary and secondary vibrations in a barrel. Not only does the barrel "wag" (muzzle displacement laterally to the boreline), literally "flopping", but there are vibrations that travel down the barrel in "packages", like pulse modulated RF. It seems to be inherent, primarily, to the metallurgy of the barrel and source energy characteristics, but common sense implies that dimensions is also part of it. The secondary vibrations seemed to change somewhat with charge and bullet weight variations, but not much. It is broad band in nature and "rides" the primary vibration curve.

Since it is generally accepted that the most desirable situation is for the bullet to exit the muzzle at the "end" of the primary displacement, (at that instant where the muzzle is nearly stationary, as it changes direction, or "peak of the node") the most desirable placement of these secondary vibration packages is as far away from that point as possible, i.e., as the muzzle is zooming past the at-rest bore line.

The problem is, once the barrel is manufactured, there is little that can be done to affect the PRF of these broadband vibration "packages". The PRF of the secondary vibration packages is not the same as the frequency of the primary vibrations. They can be damped, but not eliminated. If they coincide with a primary node at projectile exit, you will need luck or money (different barrel) to calm the beast down on paper. The trick is how to synch the PRF of the secondary vibration packages with frequency of the primary vibrations, then control one of them so as to insure you don't experience a secondary vibration package at a primary node. It's probably doable, but I surely don't know how it's done.

As far as I know, methods to deal with this interest very few people and are assuredly costly. Most would probably characterize it as "sifting through the spilled pepper to find the fly poop."

Were I independent wealthy, I would love to go there. I would be a poor candidate for such research, knowing little about materials, but I would dearly love to be rich enough to fund it.

I wonder what Art thinks about all this.
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