I've done that with a washer a good 1/16" smaller in OD than the bore! Like you said - simple and works SLICK!Loyalist Dave said:All I do is take a spent cartridge case like a spent .223 and cover the butt end with some foil, shiny side to the outside, then drop it mouth first down the muzzle, so it acts like a mirror, and use an LED flashlight to illuminate the interior.
Not that it needs to be said, but I try not to press "in" on the ID of the washer, thus to avoid making a rounded dimple.