40 gr. .223 subsonic powder loads9/12/2023 It was always an uber rare event, and when it happened, it only happened with serious underloads of slow rifle powder in large magnum cases. That would exist very briefly but would be enough to initiate cracking in steel.Īs far back as the 70s I can remember hearing about how too low a powder charge could cause a detonation. If you convert the potential energy in a fused powder mass (as you sometimes dig out of a case after a squib-out experience) to pressure, you get values local to the detonation front of about half a million psi. So that was my bad.Ī gas detonation would be slow compared to the detonation of a solid explosive, but could it initiate detonation in a hot fused powder mass? It would be interesting to explore. I'd read somewhere previously that knocking resulted from fuel/air mix detonation, but a review of current descriptive articles have detonation separated out as autoignition (though I assume it would make a knocking sound when it occurs). I will see if I can find it and make it available to you.Īs to the gas theory, I stated it is "an explanation" when I referred to it, just because the fact there is an explanation floating around in the world of explosives suggests the event had occurred enough to need explaining. Brownell was arguing against in a letter to the editor. In fact, it is exactly the position taken in a Handloading article that Dr. So a declaration that it is entirely an old wive's tale is what strikes me as speculative. You can't generate statistical outliers on demand, which makes laboratory study problematic. Most descriptions of gun bursts by light loads will be uncommon anecdotes because the event's statistical probability is so tiny. It's anecdotal reporting, and it's an interesting anecdote because a simple double charge (or even a quintuple overcharge) can't explain it, as it does with "Bullseye surprise" detonation claims in 38 Special in the past. Knocking is not even close to the supposed low charge detonation theory. Does the "theory" still exist? Yes, but based on the body of evidence, as a ballistics expert, I have seen it not allowed in court due to it being "junk science." No one with actual professional experience and knowledge gives quarter to the theory. Research the back story of where this theory originated. As such, still a theory that has never been proven. He did no testing and did not independently verify the theory. The description on page 30 is merely a recitation of the prior theories. I have in fact seen the the Master's thesis you mentioned as well. Detonation of explosive gases is not unusual. ![]() This more recent Master's thesis () by an explosives engineering student mentions an explanation on page 30 having to do with combustible vapors from powder accumulating and then igniting. But it isn't something that never happens. The extreme pressure events are very low probability outliers for the pressure fluctuations produced by loads below about 40% case fill, so an awful lot of firing usually has to be done to run into one such event. He pointed out the problem with studying the phenomenon is statistical. ![]() Lloyd Brownell reported measuring low charges very occasionally doubling normal full-load peak pressure in his laboratory measurements of the 30-06 at the U. There is in fact a description of a blown-up 308 Win rifle that nearly cost the shooter his eyesight that was loaded with just 3.1 grains of N320 described on the Finnish Gunwriter's site. You have to distinguish between NO evidence and NO evidence you've run into. NO! Old wives tale with NO evidence to support it!
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