FYI, this is a post I made on our club page this morning.
On inspecting barrels
Apparently, there is little knowledge of what you are looking at, when you look through the bore of a firearm.
I learned how to inspect a barrel at the Bauska Rifle Barrel, Co., from Les Bauska.
He told me the way to train your eye, is to first look through a shotgun barrel. You will see concentric circles the length of the barrel.
These are light bars, and there are somewhere around 100,000 per inch.
On any good barrel, you will see these are all concentric for the length of the barrel.
On a crooked barrel, you can see the light bars are oblong in the bad part of the barrel. They will show you which direction
a barrel needs bent to correct things.
This holds true on a rifle barrel, although it is a bit more difficult to read for some. Some never can be trained to see it. The bore of the barrel is a polished smooth cylinder, just like the smoothbores. The rifling is added after the bore is done.
You can train yourself to see the light bars, even with the rifling. Rough rifling is inconsequential, as long it is not cutting patches. Shoot it smooth, or lap it.
I've been the barrel inspector for three gun companies. I was able to teach some, but they were not common.
So, that gives you an idea of how to see if a barrel is straight. If you can't see and understand what you are seeing, you are
swinging blindfolded if you need to bend the barrel.