Excuse my ignorance, but could somebody please tell me what the differences are between the two weapons? I know that the Commando is a much older development, but what are the differences?

Commando is a commercial Colt trademark/designation that has been applied to a variety of short barreled, sliding stock variations of the AR-15. These weapons usually have a 10-11.5 inch barrel. Some of these may have been off-the-shelf purchases by the US military as well as by other countries. During the Viet Nam War the US type-classified the weapon for testing as the XM177, -E1, -E2, and by the Air Force)GAU-5/a/a. See:

Colt model numbers: <http://www.biggerhammer.net/ar15/variants/>

Current Colt Commando: <http://www.colt.com/colt/html/a2f14_commando3.html>

The M4 and M4A1 are type-classified current standard US military weapons. They are identical AR-15 based weapons (sliding 4-position stock, "flat top" upper receiver, 14.5 inch barrel configured for mounting the M203 grenade launcher, etc) except that the M4 fire controls are safe/semi/burst (3-round) while the M4A1 is safe/ semi/auto. See Military Specification (MILSPEC)for M4 and M4A1: <http://www.ar15.com/content/books/>

M4 has A2 style upper reciever, while the M4A1 has flattop upper.

[ 01-18-2003, 08:38: Message edited by: CHARLESARBUCKLE ]

I believe you are correct that early M4s had the M16A2 type upper receiver. However, in the mid 90's the spec was changed so that both weapons had the removable carry handle/rear sight. The technical manual for the series,TM 9-1005-319-23,(which I forgot to mention in my earlier post) is also available from the ar15.com web site and shows this.

The other significant difference between the Commando and the M4A1 is the forearm shells. the M4A1 has a slightly larger one that apparently dissipates heat better.

The Commando is noted to be a bit finiky about being clean. The gas port sizing is more critical to assure reliable operation. Once they're right ... they seem to work just fine though.

Short barreled rifles are very loud. The 10.5 and 11.5" barrels let you feel the blast on your face in rapid fire. Flash with not deterred powders is pretty amazing. The 14" barrel of the M4 is a pussycat by comparison.

The longer barrel also results in somewhat higher velocities that the shorties.

I don't know but I would assume they have different rifling twist rates as well for the different ammo used in different era's M193 55gr vs. M855 62gr.

I used a GAU in the AF for providing Security for missions to Nicaragua in the 80's. It had a 10.5 inch barrel with a 4 inch flash supressor to help burn the excess powder so the rifle would function. The twist was 1in 12inch and shot the 55 gr well. I'm sure the new 62's would go side ways through the target, which depending on the circumstanses could be a good or bad thing. I guess the M4 is all the rage for the new troops. I used the GAU and bet my life on it and it worked. May God bless the troops that use the current model. PS: Above all keep it clean and free of dirt!