09-25-2019, 11:03 PM
If you have a level smooth surface like granite table top you could stand the receiver on the front where the barrel is inserted. You could then use a light to to see if the receiver has any gap or is not level and square with the granite surface.
I have a gunsmith friend who has a lapping tool and a mill. We always lap my upper receivers but like grayfox mentioned we have only removed a small amount of material. I like having the barrel square with the receiver so there is no uneven pressure on the bolt. I always bed my barrel and upper receiver with blue Loctite and use blue loctite on my gas block and screws. I’ve done several uppers this way and they all shoot good and I haven’t had any issues with my gas blocks moving or coming loose.
I have a gunsmith friend who has a lapping tool and a mill. We always lap my upper receivers but like grayfox mentioned we have only removed a small amount of material. I like having the barrel square with the receiver so there is no uneven pressure on the bolt. I always bed my barrel and upper receiver with blue Loctite and use blue loctite on my gas block and screws. I’ve done several uppers this way and they all shoot good and I haven’t had any issues with my gas blocks moving or coming loose.