What Does it Mean to Proof a Firearm?
BY Herschel Smith
4 years ago
Proofing—as the term pertains to firearms—refers to the test of a fully assembled firearm or component of a firearm with a high-pressure cartridge, or series of cartridges in the case of a revolver, that can be as much as 30-percent higher pressure than the recommended industry safety standard for a given round.
It is essentially a stress test on a firearm or component of a firearm by firing one or more “proof cartridges” to ensure the structural integrity of the gun or part being tested. Once the proof cartridge or cartridges are fired, the gun is inspected to verify no damage to any of the parts of the gun has incurred. If none was sustained from the proofing procedure, the firearm is deemed mechanically sound and ready to enter the distribution chain.
Depending on the manufacturer and/or country of origin, the frame, barrel and slide of a pistol may be stamped with a mark signifying successful completion of the test procedure. Other firearms may have proofmarks stamped into the frame and/or the barrel by itself.
In some cases, only the barrel is tested since it is the primary component containing the pressure of the ammunition. This is usually done in product designs that have a history of durability and reliability as a cost-saving method of manufacturing.
In addition, barrels that have quick-change or drop-in capability in multiple frames are usually proofed individually and are stamped in a conspicuous location as verification that they have been tested.
When proofing a complete firearm, the whole gun must be placed in an enclosed fixture and triggered remotely for safety purposes in case of a failure during the discharge of the high-pressure ammunition.
Proofing a barrel individually is much simpler, even though it, too, must be tested in an enclosed fixture for safety in the unlikely event of failure.
The time it takes to proof a barrel by itself as opposed to a whole firearm is significantly less. From an economic perspective, this is the best option for manufacturers to take without compromising safety.
Generally speaking, once a firearm has been proofed, it is proofed for the life of the gun unless some major changes have occurred to the parts managing the pressure of a cartridge when fired. A gunsmith restoring or rebuilding a gun may have the occasion to re-proof a firearm, but for the average gun owner it should not be a particular concern.
Added to that, proof ammunition is highly regulated and generally unavailable to those who do not either manufacture or remanufacture firearms.
While not dangerous in highly specialized, extremely limited use, prolonged firing of proof ammunition would be harmful to the gun and therefore detrimental to both shooter safety and his or her investment.
It’s called proof of principle, and the principle is engineering design margin. Manufacturers who do not do this should be shunned.
I actually didn’t know that proof ammunition is “highly regulated.” It shouldn’t be. If I want to purchase it, I should be able to purchase it.
I see proof ammunition as similar to 450 SMC (or 460 Rowland), which I should only be shooting in .45 ACP guns that have been inspected and modified with a stiffer spring. Most manufacturers will tell you that, for example, our gun will shoot +P ammunition, but “We don’t recommend feeding the gun a steady diet of +P ammunition.”
How I run my gun is up to me, but I’m an engineer and I think hard about these things.
On December 1, 2020 at 1:38 am, BRVTVS said:
Back in the flintlock days, proofing involved 4 times the usual powder charge, as shown around the 15:30 mark in this old documentary about gunsmithing at Colonial Williamsburg. https://youtu.be/qTy3uQFsirk?t=930
On December 1, 2020 at 9:44 am, Ratus said:
If you want the information on proof loads SAAMI has the technical data freely available.
https://saami.org/technical-information/ansi-saami-standards/
But, I’d recommend against trying to obtain or duplicate a proof load to use in any firearm.
SAAMI proof loads are between 130% and 150% of the maximum chamber pressure for the cartridge.
For example, 9mm is proofed with the 9mm+p proof load of 55,000psi.
The maximum chamber pressure for 9mm is 35,000 psi for standard pressure loads and 38,500psi for +p.
On December 1, 2020 at 1:13 pm, billrla said:
Interesting post that contributes to my knowledge. Thanks.
On December 2, 2020 at 11:37 pm, X said:
That’s a very interesting post. I have two comments: 1) I wonder how manufacturers proofing barrels verify that the barrel did not sustain damage in the proof test. Just because the barrel did not blow up in the test does not mean it might not have suffered hairline fractures that could cause it to fail later. I PRESUME that they must randomly x-ray barrels for this, and of course they know what the steel is rated for, and what the proof pressure is. But I do not see how they could possibly check every barrel.
2) You CAN get proof ammo if you want — handload it. Of course you will not have exact data for the proof pressure, so you would have to extrapolate and take a pretty good guess how close you are to 30% over. That might sound crazy, but Ol’ Elmer Keith was shooting .44 Spl loads that were WAY past “pucker factor” and eventually this evolved into the .44 Magnum. Wildcatters have been basically guessing what a safe load is for decades. I’m sure a few guns were blown up in the process, but wildcatting is how we have a ton of cartridges today, from the .44 Mag to the .260 to the .22-250 to the .35 Whelen and a number of others.