is a proof test a double charge

[farmbif]

Ive been spending a lot of time recently loading for pistol caliber rifles and putting together a lot of loads using BE86 and unique in 357 mag, 41 mag, 44 mag and 45 colt. As getting older my attention span I guess wanders and while loading some 41 mag thought maybe I double charged one with a 10 grain charge a double charged shell would be easy to detect. Instead of whacking them all apart and starting over I weighed each round and thank goodness they all were within a grain or two.

but anyway it got me wondering if a proof load is double charge or just a bit over book max

[Outpost75]

SAAMI Max. Average Pressure is the statistical maximum individual pressure, or the maximum sample average (machine loading limit) plus 3 standard deviations. The proof pressure is ordinarily 1.25 times the MAP, which varies according to the cartridge.

[smithnframe]

Maybe they were all double charged!

[Winger Ed.]

Double of a max. charge probably wouldn't fit into very many cases without using a hydraulic press.

[johniv]

Interesting thread. Years ago (almost 50)I worked for a gunsmith, who ,in one of his convoluted trades, acquired a case of .38 spl. Proof loads. Projectileand case head stained red. He proceeded to sell these to customers whom he knew owned .357 revolvers. Not a good idea, I thought, as these could be passed on to unknowing folks who would have no idea what they had. Anyway , I never heard of any repercssions. Fast forward 45 years or so, and one day at a public range, I picked up some brass headstamped "357 BHA PROOF" . It really drives home the warning KNOW WHAT YOU ARE PUTTING IN THE CHAMBER.

[tomme boy]

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.

[uscra112]

Did they really do that? Wouldn't test the hoop strength of barrel/receiver.

[john.k]

The British WD proof load for 303 was a normal charge with a heavier bullet.....in the case of Mk7,they used a Mk 6 bullet......very simple to arrange......And as mentioned ,British proof was two shots ,one dry case,one oiled case.........Quite a few manufacturers of military rifles tested the barrel blanks after drilling and outside turning ,but before reaming and rifling ,by using hydraulic pressure......up to 100,000 psi ,....to eliminate faulty ones early in the process.....

[pocketace]

there is no real way to actually figure out what a proof load would be for a given caliber. When i talked to the people at SAAMI when i wanted to know if 5.56x45 nato was safe in a bolt action .223 remington,, they had some nice charts and in one spot it said.

that the individual chamber, in order to meet SAAMI standard had to be able to survive use of ammunition that was "125 to 150% above standard average pressure for that cartridge." Meaning that if a company was to make a brand new handgun chambered in a cartridge that has a 10,000 cup max limit, the chamber would have to survive routine use of ammo loaded to 15,000 cup.

[Outpost75]

there is no real way to actually figure out what a proof load would be for a given caliber. When i talked to the people at SAAMI when i wanted to know if 5.56x45 nato was safe in a bolt action .223 remington,, they had some nice charts and in one spot it said.

that the individual chamber, in order to meet SAAMI standard had to be able to survive use of ammunition that was "125 to 150% above standard average pressure for that cartridge." Meaning that if a company was to make a brand new handgun chambered in a cartridge that has a 10,000 cup max limit, the chamber would have to survive routine use of ammo loaded to 15,000 cup.

Actually that is all open-source information in the CIP and ANSI standards and the methodology is clearly defined. The military traditionally has used simple, practical methods for assembling proof loads. The .30-'06 proof load was a 220-grain bullet over the standard charge used for the M1906 Ball, and later the Ball M2. The .30 M1 carbine proof load substituted a 152-grain Ball M2 bullet over the standard powder charge. The 7.62 NATO proof for years used the 174-grain cal. .30 Ball M1 or later the M118 Special Ball bullet with 40 grains of IMR4198. The 9mm Parabellum proof load simply took M882 Ball and seated the bullet 1.5mm deeper.

[M-Tecs]

there is no real way to actually figure out what a proof load would be for a given caliber. When i talked to the people at SAAMI when i wanted to know if 5.56x45 nato was safe in a bolt action .223 remington,, they had some nice charts and in one spot it said.

that the individual chamber, in order to meet SAAMI standard had to be able to survive use of ammunition that was "125 to 150% above standard average pressure for that cartridge." Meaning that if a company was to make a brand new handgun chambered in a cartridge that has a 10,000 cup max limit, the chamber would have to survive routine use of ammo loaded to 15,000 cup.

Section IV of the SAAMI of each standard deals with SAAMI Proof Load pressures.

starts at page 351 for rifle https://saami.org/wp-content/uploads/2019/02/ANSI-SAAMI-Z299.4-CFR-Approved-2015-12-14-Posting-Copy.pdf

starts at page 181 for handgun https://saami.org/wp-content/uploads/2019/02/ANSI-SAAMI-Z299.3-CFP-and-R-Approved-2015-12-14-Posting-Copy.pdf

starts at page 111 for shotgun https://saami.org/wp-content/uploads/2019/06/ANSI-SAAMI-Z299.2-Shotshell-2015-R2019-Approved-2019-04-23.pdf

starts at page 78 for rimfire https://saami.org/wp-content/uploads/2019/06/ANSI-SAAMI-Z299.1-Rimfire-2015-R2018-Approved-2018-06-13.pdf

If you want actual load data for SAAMI you need to pay for it and have legitimate need and proper controls. "Note: The purchase of Reference and Proof Ammunition may be limited to individuals and businesses with legitimate need and proper controls in place. Check with the individual manufacturer for their policies." https://saami.org/technical-information/reference-proof-ammunition/

[pocketace]

paying for it last i checked required industry credentials and a research lab.

[Ozark mike]

Regardless if you use a powder with 75% load density or greater it will take great amounts of will to double charge a case thats why i like slower powders and they usually give me better accuracy

[Burnt Fingers]

Ive been spending a lot of time recently loading for pistol caliber rifles and putting together a lot of loads using BE86 and unique in 357 mag, 41 mag, 44 mag and 45 colt. As getting older my attention span I guess wanders and while loading some 41 mag thought maybe I double charged one with a 10 grain charge a double charged shell would be easy to detect. Instead of whacking them all apart and starting over I weighed each round and thank goodness they all were within a grain or two.

but anyway it got me wondering if a proof load is double charge or just a bit over book max

Weighing the completed rounds is worthless unless you've sorted your brass and boolits by weight before hand.

Take 10 random pieces of brass and weigh them. The results may surprise you.

[KCSO]

Spanish proof is a 30% overload fired three times or was.

[Larry Gibson]

farmbif

"it got me wondering if a proof load is double charge or just a bit over book max"

Post #10 and #11 give you the definition of "proof loads". A "double charge", referencing your quandary, of a reduced load of fast burning powder may or may not exceed maximum pressures (MAPs). For example; in your 41 magnum with 210 gr cast bullet if your load was intended to be 5 gr of Unique and you double charged it the 10 gr load would only be close to a maximum load. However if you were using Bullseye the double charge of 10 gr would be over maximum. Then if your load was a close to maximum 10 gr Unique and you double charged it to 20 gr then that would be way over maximum.

[robg]

not worth the risk ,tear them down

[Battis]

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?

[Outpost75]

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?

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.

[Battis]

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.

[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/why-cant-you-use-a-bolt-again-after-its-been-torqued/

https://courses.lumenlearning.com/physics/chapter/5-3-elasticity-stress-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.