There is standardization on the distance from the bolt face to the barrel extension's front face.
There is standardization of the distance from the barrel extension front face to the rear of the gas block seat.
There is standardization of the distance from the rear of the gas block seat to the center of the gas port.
Not all companies follow the standards.
If you added these figures up, you would end up with the following figures:
Carbine is 7.795" from boltface.
Mid-Length is 9.795" from boltface.
Rifle is 13.170" from bolface.
Last edited by AR15barrels; 12-04-11 at 21:00.
Randall Rausch
AR15 Barrel Guru
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