AR Sponsor
Posted: 12/7/2004 4:30:12 AM EDT
|
A2 Profile: Diameter tapers from .675" to .605" under handguards, .715" from front sight to muzzle. (Bushmaster makes them slightly differently with a .750" diameter under the sight and to the muzzle). Often called 'Govt Profile'. M4 Profile: As A2, except for small area .610" in diameter in front of sight. That 'notch' is used to allow the attachment of an M203 grenade launcher. M4A1 Profile: As M4 except slightly larger under the handguards (4oz worth of weight). There is a cut in the new heavier profile under the handguards so the M203 can still be mounted (similar to the cut in front of the front sight base). Started in FY 2001. The above is taken from the Maryland AR15 Shooters site. I want to know the barrel diameter, under the handguards, of the M4A1. Anyone? |
|
The new M4 profile is called HB by Colt. Rifle models are 6920HB and 6921HB. Our beloved  Colt dealers will be able to find one as:SP65081 BARREL & FRONT SIGHT ASSY LE6920HB, 1/7 M4HB- 16in CHROME LINED SP64958 BARREL & FRONT SIGHT ASSY LE6921 1/7 M4 - 14.5in CHROME LINED I think the best name for it is M4HB. AFAIK, it is not standard for all M4A1's, but it is to increase barrel life under automatic fire. I have a picture of the Colt HBAR, M4HB, M4, and Lightweight barrels side-by-side. It's not mine, however, but it does agree with StormSurge's number, because the heavier shank matches up with the M4's taper up to .845" before it reaches the FSB. |
|
According to Prideboss, a dealer here, the 16.1" M4HB is 2.15lbs, and the 16.1 M4 is 1.85 lbs, a difference of .3 lbs or 4.8 oz. The segment in question is only 5" long, and the diameter increase is .2" for about 1.156 in^3 of steel, which is 0.284 lbs per in^3, so 0.3 lbs is very believable. |
AR Sponsor