I'm considering building a muzzleloader at some time in the hopefully not to distant future and was thinking through some of the things I would want to do to insure the safety of the gun.

I have read several places about people "proofing" their guns with double charges and/or double projectiles and firing them with firecracker fuses and such. What I would like to know is, How do you determine if the gun has "survived" the proofing?

The obvious answer is, it didn't if it blows up. But what if it doesn't blow up but is stressed and therefore weakened but not obviously damaged? How does one quantifiably measure if the proof load did/did not damage or overstress the barrel?

One thought I had was to measure the diameter of the barrel before and after to determine if it had changed, but how much change would be too much change? Maybe it should be magnafluxed before and after to show any cracking, etc. What do you all think? Is there some place where this kind of information can be found?

Thanks in advance for any knowledge you can send my way.