Barrel straightening: from what I have read in the past the men who did the work in the factories could detect the slightest crook and correct it. I'm talking closer than .001 for its entire length. Traditional method was to have a thin line drawn on a high window and pointing the barrel at it a shadow of the line was cast inside the bore and any unevenness was readily seen by a skilled workman. This is also the method Skeet's uses. I have watched makers of muzzleloader barrels do the same thing and their ability to straighten them is amazing.

When an old man dies a library burns to the ground. (Old African proverb)