Different barrels. The M4 has the RO921 and the M4A1 has the RO921HB. The M4A1 also has an ambi safety(which is very nice) as well as a H2 buffer in the M4A1 vs the H buffer in the M4. Those will be the only civilian differences.
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Different barrels. The M4 has the RO921 and the M4A1 has the RO921HB. The M4A1 also has an ambi safety(which is very nice) as well as a H2 buffer in the M4A1 vs the H buffer in the M4. Those will be the only civilian differences.
The differences have been pretty well covered here. I'll just add that there is a very noticeable weight difference between the M4 and M4A1 barrels if you're used to one and switch to the other. My unit was one of the first to get our M4s converted over to A1s, and the added weight was very noticeable (and being grunts, it was the first thing we complained about). I know they call it a "heavy barrel", and that's a name I have to agree with. :jester:
By the way , my barrel is 14.5 inches long . Anyway , Thanks a lot to the all of you for the time and your inputs . Really appreciate them .
Since he's talking about the upper only, and not a complete rifle, I think it's conceivable that he has a take-off upper from a police or other organization's M4. I've seen a number of Colt 14.5" uppers pop up on GB that are described that way, including one that's currently listed as a former NYPD 1/9 twist M4 upper. I'm guessing it would be pretty hard to tell if this one's the real deal or an LE6921 upper, but it seems quite possible that former police uppers have been sold off from M4s that have been traded in or possible destroyed (e.g. an upper taken off an unserviceable lower).
Dave
I have a hunch it's just a standalone 14.5 upper like the ones Grant sells. He says it's probably issued, which means he has no idea.
By the way , in the upper receiver , there is an engraved laser mark of a "C" and "AF" . Also , for your information , I don't live in the U.S.. I live here in the Philippines . I purchased this Colt M4/M4A1 upper receiver in 2008 . Anyway , what are the advantages of the thicker barrel of the M4A1 as compared to that of the slimmer barrel of the M4 .Also , what are the other advantages of the M4A1 over the M4 ?
Thanks again in advance .
PS. In a way , 3ACR_Scout is right , I purchased this Colt M4/M4A1 upper receiver and barrel from someone who was part or had connections with the U.S.-Philippines Visiting forces Agreement here in the Philippines . It is a take-off upper receiver of one of the Colt M4/M4A1 loer receivers used VFA exercises here
In addition to what ABNAK stated about the barrel, the only other real difference between the two models, as previously mentioned, is the full auto fire control group in the M4A1 vs. the 3-round burst FCG in the M4. While opinions differ on the usefulness of full auto fire, I think the general concensus on this forum is that the auto FCG offers a more consistent trigger pull when firing the weapon in semi auto. The 3-round burst FCG creats a variable trigger pull as it cycles, which has a negative impact on accuracy when firing on semi.
Having carried an M4 with a full auto FCG during my first Iraq deployment, I feel that the trigger is controllable in automatic fire, to where you can fire bursts of various lengths (2-round, 4-round, etc.) without being limited to the 3-round cycle. Whether or not that's useful is up for debate.
Dave
For your information also , my M4/M4A1 upper receiver and barrel is partnered with a Colt M16A1 lower receiver.
Again , Thanks a lot for all your replies and time.