Borescopes
I would guess that everybody who does barrel chamber work,Gunsmiths/Hobbyists, owns and knows how to use a borescope. the skilled craftsman knows what he’s looking at and ,if necessary, how to correct a mistake made in the machining process.
I am not a machinist or hobbyist. Don’t own a lathe. Never will.
I do own a borescope, that I primarily use to verify the effectiveness of bore cleaning solvents. The borescope has assisted me in adopting a good bore cleaning regimen, that I'm happy with.
I have owned barrels(Brand new) that just would not shoot from the start. Looking down the bore of that new barrel ,with a bore scope ,showed nothing, that I could recognize as a reason why it wouldn’t shoot.
Maybe I just didn’t know what to look for.
I’ve had good barrels that kept shooting, when the borescope showed(According to examples) that they should have been relegated to the tomato patch.
I seldom use my borescope anymore. I use the target. When accuracy starts diminishing, I order a new barrel. and hope I get lucky.
I forgot,I did use my borescope several weeks ago to locate a water pipe ,on a DIY repair project.
Glenn