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 5999-01-417-9808
NSN 6620-00-875-6572
NSN 6135-01-265-1384
NSN 5999-01-508-7875
NSN 6145-01-383-7134
NSN 5950-01-522-9753
NSN 5935-01-450-9240
NSN 4140-00-318-0159
NSN 6610-01-443-8396
NSN 5960-01-413-3877
NSN 5950-01-021-5339
NSN 5925-00-199-9565