Bart B.
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As that barrel's wiggling at several dozen (several hundred with harmonic overtones) cycles per second, where does the external force come from that makes it stop wiggling? And where does it come from that makes it start wiggling again?
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Not an exterior force, simple inertia. As the barrel moves towards position of maximum position velocity decreases towards zero until maximum position is achieved, then it goes back the other way accelerating until it hits the halfway point towards the other maximum position.
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And barrel time for most centerfire cartridges is between 1 and 2 milliseconds, a huge spread in muzzle veloctiy would easily put each one in that 1 millisecond dead/immobile time frame.
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Which gets into Dan Newberry's "OCW" load method, or the Optimal Barrel Time load method.
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It sure contradicts Varmint Al's opinion based on physics:
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No it doesn't. The theoretical harmonic nodes Varmint Al calculated were an attempt to understand how a barrel tuner works. Node 1 would be what happens when you "pluck" the barrel from the muzzle end, Node 2 is what Bill Calfee recorded in his test. Node 2 is what happens when you fire a cartridge, which is explained in detail here:
http://www.varmintal.com/aeste.htm
Every material will have different resonant nodes depending on the input energy. You can see this with the classic "steel plate" experiments:
http://www.phy.davidson.edu/StuHome/...ges/plates.htm
Jimro