Back in the early eighties, I lived in central Georgia.
I didn't know anyone who shot black powder, there was no internet.
My only source of muzzleloading info was the Dixie Gun Works catalog.
And from there, I bought a TC Hawken, a replica .58 Zouave, and a Tennessee Mountain Rifle kit. I killed deer and wild hogs with all three rifles.
Back then, the Dixie catalog said you needed to "proof" your new rifle.
You were to load the rifle with two patched round balls. I can't remember if you increased the powder charge or not, seems like it was 80 grains, maybe 100.
This was to make sure the barrel was strong enough.
You were to put the gun in a tire and pull the trigger with a 50 foot string. You were to do this one time.
So, I did it with all three guns. No blown or bulged barrels.
In fact, it got good to me with the TC Hawken, I loaded two balls and 80 gr of powder and took 5 or 6 shots at 50 yards. At that range the balls were right on target, and 2 inches apart. I thought that would really hit a deer hard, but decided to hunt only with one ball.
So, I "proofed" an Italian barrel, and American barrel, and a Jap barrel, and they all held up.