1 - Colt built several thousand "bastardized" AR-15's using different lower receivers but the same model number. Depending on the date of manufacture it may have an A1 or an A2 lower receiver. There doesn't seem to be a definitive list of which rifles have which receiver, or when Colt began using strictly A2 receivers for their AR-15's.

Colt M16 Rifle Models

Courtesy Janes Infantry Weapons 1997/98, and Small Arms of the World (1983) by Edward C. Ezell.
 

Model  Number	Model Name	Description	Roll Marked (left)	Roll Marked (right)
601	AR-15	AR-15 rifle	Colt Armalite AR15 Patents Pending Cal. .223 Model 01 Serial 0000000
602	AR-15	AR-15 rifle. Early US Government purchase - no forward assist.	Colt AR-15 Property of US  Gov't Cal. .223 Model 02 Serial 0000000
603	M16A1	M16A1 rifle. Originally the XM16E1. Standard US Government model with forward assist.	Property of US Gov't M16A1 Cal 5.56mm 0000000
603K	M16A1	M16A1 rifle. Produced for South Korea.	M16A1 K0000000	Made in Korea Under License from Colt's, Hartford, CT. U.S.A.
604	M16	M16 rifle. Produced for US Air Force without forward assist.	Property of US Gov't M16 Cal 5.56mm 0000000
605A		M16 carbine. Carbine version of M16A1 rifle with forward assist and fixed buttstock.
605B		M16 carbine. Same as Model 605A but with additional three-round burst limiter; no forward assist.
606	HBAR	Heavy Barrel Assault Rifle (HBAR) without forward assist. Also known as the Heavy Assault Rifle M1.	Mod 606 Cal 5.56mm 0000000
606A		Heavy Barrel Assault Rifle (HBAR) with forward assist.
606B		Heavy Barrel Assault Rifle (HBAR) with forward assist and three-round burst limiter.
607		Submachine gun with sliding buttstock and 10" (254 mm) barrel.
608		CAR-15 survival rifle with 10" (254 mm) barrel and fixed tubular buttstock. About 10 produced.
609	SMG #1 XM177E1 Commando	XM177E1 submachine gun for US Army with 10" (254 mm) barrel and 3.5" (89 mm) long sound/flash suppressor.	Property of US Gov't Commando Cal 5.56mm 0000000
610	S.M.G. #2 XM177	XM177E1 submachine gun for US Air Force with 10" (254 mm) barrel.	Property of US Gov't SMG 5.56mm 0000000
610B		XM177E1 submachine gun for US Air Force with addition of three-round burst limiter.
611	HBAR	Heavy Barrel Assault Rifle. Export model of Model 606.	Mod 611 Cal 5.56mm 0000000
611P	HBAR	Heavy Barrel Assault Rifle. Export model of Model 611 for the Philippines.	Made by Elisco Tool for the Republic of The Phillipines M16A1 RP0000000	Made in the Phillipines Under License from Colt's, Hartford, CT. U.S.A.
613	AR-15	M16A1 rifle. Export version of Model 603.	Mod 613 Cal 5.56mm 0000000
613P	AR-15	M16A1 rifle. Export version of Model 613 for the Philippines.	Made by Elisco Tool for the Republic of The Phillipines M16A1 RP0000000	Made in the Phillipines Under License from Colt's, Hartford, CT. U.S.A.
614	AR-15	M16 rifle. Export version of Model 604 without forward assist.	Mod 614 Cal 5.56mm 0000000
614S	AR-15	M16 rifle. Export version of Model 614 license produced by Chartered Industries of Singapore.	C I S Made in Singapore by Chartered Industries of Singapore Limited Under License from Colt Industries Hartford, Conn, USA Patented
616	HBAR	Heavy Barrel Assault Rifle. Export version of Model 606.	Property of US Gov't Mod 616 Cal 5.56mm 0000000
619	S.M.G.	Submachine gun. Export version of Model 609.	Mod 619 Cal 5.56mm 0000000
620	S.M.G.	Submachine gun. Export version of Model 610.	Mod 620 Cal 5.56mm 0000000
621	HBAR	Heavy Barrel Assault Rifle. Heavy barrel version of Model 603.	Property of US Gov't Mod 621 Cal 5.56mm 0000000
629	XM177E2	XM177E2 submachine gun for US Army with 11.5" (292 mm) barrel and 4.5" (114 mm) long sound/flash suppressor.	Property of US Gov't XM177E2 Cal 5.56mm 0000000
630		Submachine gun for US Air Force without forward assist and 11.5" barrel.
633		9 mm submachine gun with 7" (178 mm) barrel and mechanical buffer.
633HB		9 mm submachine gun with 7" (178 mm) barrel and hydraulic buffer.
634		9 mm submachine gun with 10.5" (267 mm) barrel, without forward assist.
635		9 mm submachine gun with 10.5" (267 mm) barrel, without forward assist.
639	S.M.G.	Submachine gun. Export version of Model 629.	Mod 639 Cal 5.56mm 0000000
640	S.M.G.	Submachine gun. Export version of Model 629 without forward assist.	Mod 640 Cal 5.56mm 0000000
645		M16A2 rifle. Standard US Government model with revised 1 in 7" (1 in 177.8 mm) rifling, 20" (508 mm) barrel and new rear sight.
645E		M16A2 rifle 'Enhanced'. Modified M16A2 with removable carrying handle for optical sight mounting and flip-up front sight.
649	S.M.G.	Sumachine gun. For US Air Force, with 14" (356 mm) barrel and 1 in 12" (1 in 305 mm) rifling.	Property of US Gov't GAU-5/A/A Cal 5.56mm 0000000
651		M16A1 carbine. Export model with 14.5" (368 mm) barrel and full size stock.
652		M16A1 carbine. Export model with 14.5" (368 mm) barrel and full size stock, but without forward assist.
653		M16A1 carbine. Export model with 14.5" (368 mm) barrel and sliding stock.
653P		M16A1 carbine. Export model with 14.5" (368 mm) barrel and sliding stock, license produced in the Philippines.	Made by Elisco Tool for the Republic of the Phillipines M16A1 RP0000000	MAde in the Phillipines Under License from Colt's, Hartford, CT. U.S.A.
654		M16 carbine. Export model without forward assist. Fitted with 14.5" (368 mm) barrel and sliding stock.
655		M16A1 sniper rifle. Experimental model with high profile upper receiver.
656		M16A1 sniper rifle. Experimental model with low profile upper receiver and Sionics suppressor.
701		M16A2 rifle. Export model with full automatic in place of three-round burst limiter.
702		M16A2 rifle. Export model for United Arab Emirates with M16A1 rear sights and full automatic in place of three-round burst limiter.
703		M16A2 rifle. Export model for the United Arab Emirates with M16A1 barrel profile and full automatic in place of three-round burst limiter.
705		M16A2 rifle. Export model with full automatic in place of three-round burst limiter.  Also known as M16A2E3.
707		M16A2 rifle. Export model with three-shot burst limiter and M16A1 barrel profile.
711		M16A2 rifle. Export model with M16A1 rear sight and M16A1 barrel profile.
715		M16A2 rifle. Canadian version of M16A2 rifle known as C7 with M16A1 rear sight and M16A2 barrel. License produced by Diemaco.
719		M16A2 rifle. Version of Model 715 produced by Colt with three-round burst limiter.
720		M4 carbine. Originally known as M16A2 carbine, with 14.5" (370 mm) barrel.
723		M16A2 carbine. Produced for United Arab Emirates and US Army Delta Force. With M16A1 rear sight, 14.5" (370 mm) barrel and full automatic fire capability.
725		M16A2 carbine. Canadian version of M16A2 carbine known as C8 with M16A1 rear sight and M16A2 barrel. License produced by Diemaco.
725A		M16A2 carbine. Export version of the M16A2 carbine produced by Colt for United Arab Emirates with M16A1 barrel profile.
725B		M16A2 carbine. Export version of M16A2 carbine with M16A2 barrel.
727		M16A2 carbine. Carbine with full automatic fire feature produced for (among others) the US Navy. With 14.5" (370 mm) barrel.
733		M16A2 Commando. Short-barrelled model with full automatic fire, 11.5" (290 mm) barrel and M16A1 rear sight.
733A		M16A2 Commando. Short-barrelled model with three-round burst limiter in place of full automatic fire, 11.5" (290 mm) barrel and M16A1 rear sight.
735		M16A2 Commando. Similar to Model 733 but with three-round burst limiter.
737		M16A2 Heavy Barrel Assault Rifle (HBAR). With M16A1 rear sight.
741		M16A2 Heavy Barrel Assault Rifle (HBAR). As Model 737 but with M16A2 rear sight.
750		M16A2 Squad Automatic Weapon (SAW). With 20" (508 mm) barrel, bipod and front handguard assembly. Fully automatic.
901		M16A3 rifle. Similar to Model 701 but with flat top rail under carrying handle. Fully automatic.
905		M16A3 rifle. Similar to Model 705 but with flat top rail under carrying handle. Three-round burst limiter.
925		M16A3 rifle. Similar to Model 725 but with flat top rail under carrying handle. Three-round burst limiter.
927		M4A1 carbine. Originally known as M16A3 carbine. Similar to Model 727 but with flat top rail under carrying handle. Fully automatic. In production for Joint DoD Special Forces.
941		M16A3 Heavy Barrel Assault Rifle (HBAR). Similar to Model 741 but with flat top rail under carrying handle. Semi and fully automatic.
942		M16A3 Squad Automatic Weapon (SAW). Similar to Model 741 but with flat top rail under carrying handle. Fully automatic only.
950		M16A3 Squad Automatic Weapon (SAW). Similar to Model 741 but with flat top rail under carrying handle. Fully automatic only.

Definitions

Barrel terms

HBAR:      Heavy BARrel, Heavy Barrelled AR, Heavy Barrelled Automatic Rifle, Heavy Barrel Assault Rifle
.223:          .223 Remington, 5.56 x 45 mm NATO cartridge
9x19mm:   9 mm Parabellum cartridge
.22 LR:     .22 Long Rifle rimfire cartridge
1:7":        Rifling in the barrel twists clockwise, with any one groove making a complete revolution every seven (7)
                  inches (178 mm).
1:9":        Rifling in the barrel twists clockwise, with any one groove making a complete revolution every nine (9)
                  inches (229 mm).
1:10":       Rifling in the barrel twists clockwise, with any one groove making a complete revolution every ten (10)
                  inches (254 mm).
1:12":       Rifling in the barrel twists clockwise, with any one groove making a complete revolution every twelve
                  (12) inches (305 mm).

Barrel contour/slip ring/handguard terms

Standard:    Original thin barrel style.  Did not stand up to prolonged firing very well giving reduced accuracy.
A2:               Later style of barrel that was tapered at the front sight to thicken the exposed barrel.  Apparently to
                     strengthen the barrel to avoid bending when G.I.'s used it as a pry bar.
HBAR:        Latest style of barrel that is the same thickness the enitre length through, rather than just the exposed
                     section.  Stands up to heat well and gives better accuracy.
HBAR
stepped:      New barrel for the M4 carbine designed specifically with a "step" to accomodate the M203 grenade
                     launcher.
Straight:      Slip ring retainer between the handguard and the upper receiver that has a straight cylindrical shape.
                     Typically found only on early AR-15 and M-16 rifles with A1 upper receivers.
Tapered:     Slip ring retainer between the handguard and the upper receiver that has a slight conical shape. Used on
                    all new AR-15 and M-16 rifles.
Smooth
triangular:  The original handguard used on early AR-15 and M-16 rifles.  Still commonly seen today, not used on
                   newer rifles. The handguard is a smoothened triangle shape with vent holes at the top.
Ribbed
cylindrical: Newer handguard used on all modern AR-15 and M-16 rifles.  Cylindrical rather than triangular, it has
                   vertical ribs along the entire length of the handguard for better grip.  Vent holes are along the top and
                   bottom.
Ribbed
shorty: Identical to the Ribbed cylindrical handguard found on modern AR-15 and M-16 rifles, the shorty
                   handguard differs only by being shorter to accomodate shorter barrel lengths.
Smooth
cylindrical: Special handguard found only on the 7" barrel of the 9mm Model 633.  It has no ribs and is smooth
                   along its entire length.
Square
LMG: Bulky square handguard used on the M16A2 Machine Gun to vent heat as efficiently and quickly as
                   possible.  Has several holes in the top and bottom to accomodate special attachments such as a vertical
                   foregrip and carrying handle.

Flash hider terms

3-prong:    Vietnam-era flash suppressor with three slits and an open front end.  Soon changed to closed end after
                  vegetation frequently got caught in the prongs.
Birdcage: Newer style of flash suppressor that has six openings with a closed front end.  Changed to A2-style to
                  prevent dust kickup when firing.
A2-style: Latest Colt flash suppressor that has five openings (two to either side, two diagonally upwards, and one up) and
                  a closed front end.  The lack of holes in the bottom of the suppressor avoids kicking up dust when firing.
Vortex:     A highly efficient flash suppressor that eliminates all muzzle flash even from very short barrels. Typically
                  four-pronged and 1/2" longer than the 3-prong suppressor.  Newer models have the prongs twisted
                  slightly counterclockwise.

Sight style terms

A1:            Original style rear sight that was adjustable for windage only.  Adjustments required the use of a tool or
                  bullet tip.  Flip-type aperatures for short and long-range shooting are provided, the ranges depending on
                  the firearm.
A2: Newer style rear sight that is adjustable for windage and elevation up to 800 meters, and requires no tools
                  for adjustment.

Receiver terms

A1:            The original, non-reinforced, slab-sided lower receiver with the exposed magazine release button.  Easily recognizable by the smooth right side.  Usually accompanied by a straight pistol grip.
A2:        Newer lower receiver with reinforcing around the magazine well and a "fence" around the magazine release button.
Flattop:     New style of receiver that lacks the carry handle.  Allows for the mounting of a wide variety of optical
                  sighting devices and accessories.

Grip terms

Straight:   First production pistol grip.  Was straight and had no notches or contours for the fingers or the hand.
Grooved:  Later production pistol grip, now standard on all new AR-15 and M-16 rifles.  Slightly thicker grip with
                 a notch for the middle finger for a better grasp.
 

 

This page copyright (C) Andrew Krywonizka, 1998-1999.  All rights reserved.  This page may not be reproduced, mechanically or electronically or otherwise, without express written consent from the author.  The Colt logo is a registered trademark of Colt's Manufacturing Company, Inc.

Last Modified on September 24, 1999
aalbert@biggerhammer.net