My son Sean has been installing HVAC at a man's home, and the fellow has numerous rifles and shotguns. He might sell his Colt AR-15 to my son, and neither of us know how to evaluate it. Its serial number is SP1 1993. Sean thinks it's from around 1960.
What should we look for? Are gauges available to check muzzle and throat wear? Will appreciate any advice you can provide.
Louis of PA