straightshooter wrote:on_one_wheel wrote:"Normal" or working pressure = ~55,000psi
Manufacturers estimated yeild point >85,000psi
Using the pressures given in the video, If my calculations are correct, That's an additional 55% pressure, giving .5 (point 5) designed margin of safety for that particular firearm.
I would have thought that firearms would have a much larger margin of safety than that.
It would be interesting to look at what margin of safety is built into some of our popular firearms.
Ackley's book details destructive tests on various actions, mostly ex military,
The Serbu RN-50 is an extremely cheaply made firearm that relies on a hand threaded end cap for breech containment.
I suspect that the designer, Professor Bubba, had little to no idea of the behaviour of threaded joints under stress.
Also in the US proof testing seems to be at the whim of the manufacturer.
Note the phrase "Manufacturers
estimated yield point >85,000psi"
Not an estimated yield, that is the calculated yield of that thread dimension in that material.
Mark Serbu is well aware of the properties of the materials he uses.
A 50BMG proof round only increases pressure from 64,000psi to 75,000psi, +17% over design pressure. The threaded joint was designed to withstand 85,000psi, so the pressure was higher than that. I don't think anybody can claim that that cartridge was within design pressures.
These rounds sell for US$100 apiece, thus people fabricate them for profit. I don't know if forensic testing can determine the specific propellant that was burned, but I think that is the suspect. With the shortages in the US currently, somebody probably just filled a case with whatever powder they could find and sold it on.