don't any one proof barrel.
A lay person can perform a crude test of a barrel...,
A trained person can perform a rather in depth test, or can have it done by an engineering firm..., for example we had a used artillery barrel on our militia cannon, and had it magnafluxed, back in the 1990's, and again when we went to sell it.
BUT to actually "proof" a barrel, which is a highly specific term that carries legal results, that barrel MUST be submitted to a proper "proof house" for testing, and upon completion, that barrel gets a "proof stamp" and the person or company selling it may claim the barrel has passed "proof".
Modern cartridges are standardized for proofing pressures, BUT black powder barrels to be proofed at a legit proof-house meet that particular house testing standard for black powder proof, and the proofing houses do not use the same standards when it comes to proofing black powder barrels.
There is no such proofing house in North America, and no barrel made in the United States is "proofed". They may, however, be tested.
So the next time somebody says
"I proof all the barrels that I use...," well, they didn't, but they may have performed some sort of test.
LD