is a proof test a double charge

[Outpost75]

Interesting. I started wondering about proof tests when I was mostly into cap and ball revolvers, which is a different animal as far as overloading with BP. Whenever I read about a modern gun blowing up with no apparent cause, I wonder if the proofing weakened it, or at least highlighted a flaw.

The modern gun blowups I am aware of were mostly metallurgical failures or design defects which could have been avoided had the manufacturer done its due-diligence on inspection, design, testing and failure analysis. S&W Scandium revolver failures and Glock ka-booms are perfect examples.

A common cause of burst barrels is improper cropping of the billets in the steel mill, such that a shrinkage cavity may remain in the center of the billet, which is then elongated when the steel is rolled into bars at the mill. That is the reason when I was at Ruger our metallurgist witnessed the cropping of billets at the mill, and discarded the 1-top and 2-top cuts for remelting, the ends of bars cut off, polished for metallalography, the cut-offs inspected with dye penetrant, barrels, frames and cylinders magnetic particle inspected using the wet method with continuous circular magnetization after proofing.

In the 1980s a well-known, famous name manufacturer skimped on revolver proofing on a government contract, firing only one proof load and regular service loads in the other five charge holes, until they were caught...

When you buy the low-priced spread corners get cut and you get what you pay for.

[303Guy]

Or do as the Brits did with the 303. Oil on the case and fire. It will create a very high bolt thrust that acts like a overcharge proof load.

My understanding is that the oil is there to apply the full case thrust of proof loads onto the bolt face. Without the oil, as much as 10 % of the thrust might be held by the case gripping the chamber walls. The Brit case doesn't hold as much thrust as a 308 case does but at the lower operating pressure it holds proportionally as much of the thrust (more or less).

[2A-Jay]

I have had to empty and redo a batch of 50 cases because of dropping dropping a charged case onto my reloading block. I learned to always use 2 reloading blocks. one for primed empties the other for charged cases. I dispense a charge and Weigh each charge and trickle up to my intended charge before dumping it into the case. Doesn't matter handgun or rifle rounds. Have not yet had an actual double charge, But then again I have only been reloading 15 years.

[M-Tecs]

I've always wondered about proof loads...can they weaken the metal of the firearm? I mean, the gun might pass the test, but what about 50, 100 or whatever shots later?

Short answer is no proof loads do not weaken the firearm. Almost all material are somewhat elastic and this elasticity allows for a specific cycle life. Oversimplified answer is the more you stretch the material the less cycles you will get before a failure. Each material has a point if you stretch it beyond that limit the material is permanently weaken. In the case of firearms the proof loads do not exceed the elastic limits of the material but as Outpost75 pointed out the increased pressure can be used to simulate a higher cycle count.

When I was in industry an "accelerated endurance test" which the government accepted as a lower cost option than firing 10,000 rounds, was to fire 364 proof loads. I don't know how Picatinny came up with that number, but every day we selected a rifle at random, fired 364 proof loads through it, then tore it down, gaged, ultrasonic and xray inspected it and never had any issues. This was in 5.56mm.

The rifles subjected to the accelerated endurance test were tagged and also turned over to the government for inspection. Occasionally we received one back after they had put another 10,000 rounds through it and they requested a new barrel be put on it. So we did.

Some light reading for your enjoyment here:

https://www.electronicfasteners.com/...-been-torqued/

https://courses.lumenlearning.com/ph...ss-and-strain/

[DocSavage]

Not an expert but I was under the impression proof loads were 30% above SAAMI norms for that particular cartridge.

[yeahbub]

Instead of whacking them all apart and starting over I weighed each round and thank goodness they all were within a grain or two.

If you suspect an error on one round and are certain of the rest, the likelihood of being correct with the weighing test seems pretty good. Those of us who have had a pistol let go in our hands or seen it happen have learned from experience how unpleasantly final an overlooked error can be. Having been in the situation you describe, I did the weight test AND disassembled the ones that weighed heavy to be absolutely certain I wasn't missing something. I've never had loaded rounds weigh within 1 or 2 grains of one another. Usually the variation was greater, but the cases were not of the same lot. Even the boolits varied more than that by themselves. I wish you well.

As an aside, since then and because of other minor errors, I've come to have respect for my fallibility. I have abandoned charging a number of cases in a loading tray, visually checking the powder charge and then seating boolits. These days, from a bowl of prepped cases, I charge one, seat a boolit, then put it in the tray. This is works for me.

[303Guy]

As an aside, since then and because of other minor errors, I've come to have respect for my fallibility. I have abandoned charging a number of cases in a loading tray, visually checking the powder charge and then seating boolits. These days, from a bowl of prepped cases, I charge one, seat a boolit, then put it in the tray. This is works for me.

I went the other way round. I used to fully load each cartridge before putting them down. After a near mishap (loaded one without powder), I now will not seat a bullet until I have placed the charged cases, be it just one or a tray full, in the tray and shone a light down into each one to check for powder presence and powder level. I haven't had an unpowdered round since. That's what works for me.

The important thing is to respect our fallibility.