The Complete Guide to Colt M-16 Models: Part II – Small Arms Review https://smallarmsreview.com Explore the World of Small Arms Tue, 10 Oct 2023 18:23:50 +0000 en-US hourly 1 https://wordpress.org/?v=6.9 https://smallarmsreview.com/wp-content/uploads/2020/05/cropped-online-sar-logo-red-32x32.png The Complete Guide to Colt M-16 Models: Part II – Small Arms Review https://smallarmsreview.com 32 32 The Complete Guide to Colt M-16 Models: Part II https://smallarmsreview.com/the-complete-guide-to-colt-m-16-models-part-ii/ Sun, 01 Mar 1998 23:46:00 +0000 https://dev.smallarmsreview.com/?p=441 By Dan Shea

Colt 613 M16A1. Birdcage flash hider, forward assist, chrome bolt carrier. This is the commercial non-government version of the military Model 603 M16A1

As we continue the SAR Identification Guide to the Colt Models, we have taken into account the requests of the readers who wanted close ups of some of the differences between the models. In this issue, we have three pages of guns, followed by three pages of comparative features. If you have other data to add to this ID Guide, please contact SAR and we will try to get it included.

Colt 614 M16. Birdcage flash hider, no forward assist, chrome bolt carrier. This is the commercial non-government version of the military Model 604 M16
Colt 619 “Commando”. Special flash/sound suppressor, forward assist, 10” barrel, collapsible stock, no bayonet lug, full pistol grip. The 619 is the commercial non-government version of the military Model 609 “Commando

The entire period that the M16 series has been in use by the United States military has been full of change. Each branch of the service has imposed it’s own criteria on the manufacturers, and Eugene Stoner’s original brilliance is evident in the adaptability of the design. Stoner’s system was balanced between all the forces at work in the firearm. Time that the system was pressurized dictated barrel lengths that would work, stroke needed for timing and recoil did the same on the buttstock. This ID Guide should serve to illustrate the diversity of designs that have been implemented in the last 40 years since his first prototype was made.

Colt 621 “H-Bar”. Heavy barrel, birdcage flash hider, M-60 bipod legs, forward assist. This variant of the Model 603 M16A1 is a true heavy barrel. Use of the M60 GPMG extendable bipod legs simplified parts inventories. The heavy barrel extended all the way over the course of the contour.
Colt 633 “DOE” Gun. 7 inch barrel, 21 inch overall with stock collapsed . 3/4 length dust cover and port buffer. This 9mm version of the SMG was made for the Department of Energy. The overall length extended is 24.25 inches. Very compact, with a front handguard to keep from losing control.
Colt 635 “SMG”. Birdcage flash hider, plastic buttstock. Collapsible buttstock, overall length of 28.8 inches. Only 5.75 lbs. 10 inch barrel. The SMG is a 9mm mainstay in many police departments. The semi-automatic version is the Model 634. Early models did not have the 3/4 dust cover and port buffer.
Early charging handles in the first model AR-15’s were in the carrying handle slot similar to the AR-10. Probably 50 made.
The first Colt bolt closing devices were an upper guard on the charging handle- these would only be found on some of the Model 601’s.
Model 601 and 602 had this charging handle. On the rifle in the picture, you will note a strange metal shape with a push button on the left hand side of the upper receiver. This was a prototype forward assist. Many people felt that operating devices should be on the left hand side of a rifle, to keep from breaking the trigger position of the right hand.
From Model 603 on the “M16” charging handle has been used, with minor variations. The sizing presents a positive grip, as well as an easy to activate unlocking device.
With the exception of the Model 610B, the slip ring that allows for the removal of the two forearm shells has stayed pretty consistent. This is the root of where the “Buddy” system for M16 disassembly came from, because it took three hands to activate this and remove the shells.
With the advent of the M16A2 design came the “Delta” ring. The angles on the new slip ring greatly enhanced the takedown speed for the operator.
Typical A1 rear sight- two aperture flip up “Peep” type
Typical A1 front sight- post type, adjustable, 5 notches
Experimental A1/A2 rear sight dial
Experimental A1/A2 front sight dial

M16A2 fully adjustable rear sight
M16A2 front sight- post type, adjustable, 4 notches
Left: A1 5 notch sight adjusting tool,
Right: A2 4 notch tool
Left: “Tear drop” A1 forward assist,
Right: round A2 forward assist
Left: standard M16 buttstock, Right: the new trapdoor buttstock for the M16A1 and M16A2, with storage space for the cleaning kit.
Left: Typical early model A1 pistol grip, still had the sling position hole. Right: M16A2 style pistol grip- no sling hole, finger grip is added on the front
Front: M16 or M16A1 buttstock, showing the one inch longer M16A2 buttstock behind it.
What is commonly referred to as a “Slabside” magazine well, that is on the early models- the “01” and “02” in particular.
The “Ridges” that have been added form a protective well around the magazine release
The early bolt hold open device, the “Bolt catch”, had a ridged surface all the way on the exposed surface, but it was difficult to engage it without the magazine follower.
Later models have the extension.
This article first appeared in Small Arms Review V1N6 (March 1998)
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