A sighting device, usually a disk or segment with a central peephole, so designed to fit in the breech end of the gun tube for the purpose of aligning the sights with the gun.
NSN 5855-01-236-9645
NSN 6145-01-455-8785
NSN 5855-01-175-2465
NSN 5990-00-281-4164
NSN 5996-00-230-4332
NSN 6145-00-278-0697
NSN 7035-00-834-2090
NSN 7035-01-024-9511
NSN 6650-00-471-1117
NSN 5925-01-360-5605
NSN 6610-01-542-9725
NSN 5975-00-199-9563