Here is a little info that may give you some idea.
In the early 1980s, at the request of the United States Marine Corps, Colt upgraded the M16A1 rifle, resulting in the M16A2 rifle. Among the major changes were a reinforced lower receiver, a case deflector, a birdcage flash suppressor redesigned to be a muzzle brake, and a barrel with a faster 1-in-7 twist. The faster barrel was necessitated by the switch from the 55 grain M193 bullet to the 62 grain M855 bullet. The M16A2 rifle's barrel was also thicker for the portion in front of the handguard. Colt incorporated these changes into its carbines, which it called M16A2 carbines. The Model 723 M16A2 carbine used the iron sights of the M16A1, but had a case deflector. The barrel had a 1-in-7 twist, but the thinner profile of the older M16A1 carbine's barrel. As with the Model 653, the United States military made small purchases of the Model 723 for its special operation forces.[8] It was notably used by Delta Force operators from the late 1980s to the early 1990s.[9]
In 1983, Diemaco developed a carbine similar to the Model 723, the C8 carbine for use by the Canadian Forces. The original C8s were built by Colt as the Model 725. In 1984, the U.S. government asked Colt to develop a carbine with maximum commonality with the issue M16A2. Colt named the carbine as the XM4. The project would eventually culminate in the development and official adoption of the M4 carbine in 1994.
Though Colt has focused its attention on carbines with 14.5-inch (370 mm) barrels and rifles with 20-inch (510 mm) barrels, Colt continues to make carbines with 11.5 inches (290 mm) barrels, which it calls Commandos. Originally, Commandos were assembled from whatever spare parts are available, so Model 733 Commandos could have A1-style upper receivers with case deflectors or A2-style upper receivers, and M16A1-profile 1:7 or M16A2-profile 1:7 barrels. Depending on the specific models, Commandos may have had three-position fire control groups (safe/semi-automatic/three-round burst), or four-position having both full-automatic and burst. The modern Model 933 has a "flattop" receiver, with a removable carrying handle and a MIL-STD-1913 Picatinny rail, with semi-automatic and automatic fire. The Model 935 Commando has the features of the Model 933, but has three-round burst fire instead of automatic. Though originally called the M16A2 Commando, Colt now markets them as the M4 Commando.
The production on the Model 733 may have ended about the same time as the Model 723 and 727 or maybe up to a couple years afterwards.
"A Bad Day At The Range Is Better Than A Great Day Working"
USMC Force Recon 1978-1984
US Air Force Res. 1995-2004 (Air Transportation)
M16/AR15 shooter since 1978, gun collector and AR builder since 2004
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