Nra Rule 3.1.2 Explains What You Can Do With Your Rear Sight App.
3.1.2 Service Rifle - U.S. Rifle, Caliber 5.56 mm M16 series as issued by the U.S. Armed Forces, or the same
type and caliber of commercially procured rifle, without biped or grenade launcher, having not less than a 41/2
pound trigger pull, with standard-type stock, pistol grip, hand guard, and leather or web sling. The rifle must be so
modified as to be incapable of automatic fire without removing, replacing, or altering parts. In all courses of fire and
in all positions the standard 10, 20-round or 30-round box magazine or a reduced capacity magazine of the same
external dimensions will be attached. The gas system must be fully operational. External alterations to the barrel,
upper and lower receivers, stock, hand guard, or pistol grip will not be allowed, except that a device may be
attached to prevent selector lever movement to the auto position. The front and rear sights must be the standard
design. The rear sight aperture and front sight width may vary in dimensions to suit the shooter. The rear sight
aperture may be hooded. Versions or adaptations of the M16 type rifle consisting of external modifications or
alterations, will be shot as an NRA Match Rifle, except as allowed in Rule 3.1.3. The trigger weight of these
versions or adaptations will not be less than 4 ½ pounds, except as noted in Rule 3.3.1. A case deflector (D.C.-T-
30 or commercial equivalent) is allowed.
3.1.3 Service Rifle - Any rifle or modified rifle not covered by NRA Rules 3.1, 3.1.1 or 3.1.2, but permitted by
CMP Rules are considered service rifles in NRA sanctioned competition.