M4/M4A1 question

[Slater]

Do the current military issue M4/M4A1 weapons have a heavier profile barrel than was the case when they were first introduced?

[Mortech]

If I remember correctly , the barrel profile has always been the same .

[jhs1969]

Some heavy profile bbls were made for spec ops to help with some of their specific problems. I don't think they are in wide spread use. Only time I ever saw one was a small arms review article about Colt M4's.

[M4builder]

The M4A1 is the R0921....with a SOCOM profile it is a R0921HB.

Civvy versions are; the 6920HB available from SAW, and the 6921HB (14.5" SBR).
You can get the SOCOM barrel from SAW, but it will set you back 5 bills +, that's just the barrel assembly.

CMMG offers both profiles also, if you want to save half the cash.

http://i192.photobucket.com/albums/z96/M4builder/CMMGBarrels.jpg

This is why the SOCOM barrel came about.
Full auto from the A1 was building up too much heat. The standard M4 used 3 rd burst, and the gov't profile held up well enough there, but it failed just to the rear of the FSB when used in sustained fire with the M4A1.

http://i192.photobucket.com/albums/z96/M4builder/destructivetestedbarrrels01copy.jpg
Thanks to GT for the great pic.
Notice how the 16.1" barrels blew out more?

[scottryan]

Before 2000, the M4 and M4A1 used the same barrel. During 2000 to the present, the M4A1 has used the heavier profile.

[Slater]

This was Armalite's take on the M4's early problems. Evidently the dynamics of the gas port is no longer an issue:


http://www.armalite.com/images/Tech%20Notes/Tech%20Note%2048,%20Barrel%20Design,%20Heat,%20and%20Reliability,%20030824….pdf

[Army Chief]

The HB does add about a pound (the LE6920HB weighs in an an even 7.0), but isn't especially objectionable on a lightly-configured carbine. Add a lot of additional gear, and it quickly becomes a factor if you're doing a lot of carrying.

The HB LE model from SAW is/was a limited run of 300, though, so while Ken Elmore is still selling off a few from his personal collection, they are not a catalogued model, nor are they widely available -- unless you are willing to pay north of $2k on an auction site. That's a nice barrel, but a very steep tarriff for something that is essentially optimized for use on a select-fire weapon.

Chief