Is this an M4 upper?

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[ARCHIVED THREAD] - Is this an M4 upper?

Posted: 8/13/2003 3:52:28 PM EDT

Ok, here's the story. Saw an add on Ebay for a Colt upper. No picture, hardly any description. After emailing the seller, he repies he does not know much about uppers, but he is sure it's unfired, a Colt, it's a flattop, it has a 16" barrel, and is pre-ban configuration. I offered him $350 to end early, and he took it. Kind of a risk, but for a Colt upper (no b/c/ch), how could I go wrong? I got it today, and it was as he said. BUT, it looks exactly like my M4 upper, except the barrel is 1/9, and my M4(that I know for SURE is an M4) has a 1/7. Same length handguards (they may be a little slimmer, but didn't have a lot of time to check them one on one), M4 feedcuts, birdcage flashider, regular sling adapter instead of side sling, has the M203 cutdown. The barrel is marked "CMP 5.56 Hbar, 1/9" SO, what do I have here? Regardless, it's going to end up as an M4 style, I have new green furniture on order already, but want to know what this may have left the factory as, or if I just got a smoking deal on an M4 upper. Thanks for the info!

Posted: 8/13/2003 4:54:26 PM EDT

[#1]

Yes, barrels are available in both 1/7 & 1/9. Is there a "4" or "M4" on the front of the upper receiver, above the clover leaf?

Posted: 8/13/2003 6:14:07 PM EDT

[#2]

I have heard people say to look for the 4 or M4, but where should I look exactly? I always thought you had to look by the gas tube, which ment taking off the handguards, which I never do unless I am forced to, lol.

Posted: 8/13/2003 6:37:22 PM EDT

[#3]

Look right above the hole where the gas tube enters the upper receiver, on the front of the upper receiver. You won't need to take anything off to find it. Thanks.....Chad

Posted: 8/13/2003 9:38:45 PM EDT

[#4]

Yep, I see it now, it has a #4 on it. Pretty good gamble on my part I guess, lol.

Posted: 8/13/2003 9:54:31 PM EDT

[#5]

Just noticed no M203 cutdown. Is this still considered an M4?

Posted: 8/14/2003 12:15:23 AM EDT

[#6]

Quoted:
Just noticed no M203 cutdown. Is this still considered an M4?

View Quote

No not an M4. I beleive most of the Colt Carbine models have M4 feed ramps these days.

Just make sure it has a chrome lined bore as well as the chamber. A lot of Colt models have chrome in the chambers only. If the bore is chrome lined it should also have "C MP B" on the barrel.

Is it skninny under the handgaurds and heavy in front of the handguards or is it skinny all the way, or is it heavy all the way?

Posted: 8/15/2003 8:19:39 PM EDT

[#7]

You have a R6721 upper. That was a steal for $350. They cost double that, new, without the b/c and ch.

Posted: 8/15/2003 9:02:07 PM EDT

[#8]

[:)] [snoopy]

Posted: 8/15/2003 10:02:32 PM EDT

[#9]

Heavy all the way, just took the handguards off. Also, no B after CMP, does this mean it's not chrome lined? I was under the impression that most Colts did have chrome bores. Thanks for the info everyone!

Posted: 8/15/2003 10:06:48 PM EDT

[#10]

Just looked at my M4 upper, and it also has CMP, with no B. I am almost positive that all M4 barrels are chrome, so what gives with the "B"?

Posted: 8/16/2003 12:08:30 AM EDT

[#11]

No M203 step down means it is not a M4 profile barrel. The HBAR would also indicate it is not an M4 barrel. Who cares, as long as you like it, it doesn't matter.

Posted: 8/16/2003 5:17:49 AM EDT

[#12]

IF it does not have a "B", does it mean it's not chrome lined?

Posted: 8/16/2003 5:26:00 AM EDT

[#13]

Quoted:
IF it does not have a "B", does it mean it's not chrome lined?

View Quote

If it was stamped with a "B" then it would be a Bushmaster barrel and not a Colt.

Posted: 8/16/2003 10:05:53 AM EDT

[#14]

You got a good deal regardless, congrats!

Posted: 8/16/2003 10:39:22 AM EDT

[#15]

Quoted:

If the bore is chrome lined it should also have "C MP B" on the barrel.

So this is not accurate info? It's hard to tell if a bore is chrome lined, and I want to make sure, as I clean chromed and non-chromed bores with differant solvents.

Posted: 8/16/2003 2:46:30 PM EDT

[#16]

Quoted:

Quoted:

If the bore is chrome lined it should also have "C MP B" on the barrel.

So this is not accurate info? It's hard to tell if a bore is chrome lined, and I want to make sure, as I clean chromed and non-chromed bores with differant solvents.

View Quote

I know on the new barrels, that the "B" after the "C MP" stands for chrome lined bore as most of the civilian barrels now do not have chrome lining in the bores. This barrel could have been made before they stopped lining the bores of some barrels because there was no reason to mark them as such before. The best way is to look.

Posted: 8/16/2003 2:47:17 PM EDT

[#17]

Quoted:

Quoted:
IF it does not have a "B", does it mean it's not chrome lined?

View Quote

If it was stamped with a "B" then it would be a Bushmaster barrel and not a Colt.

View Quote

I was saying that it would be marked "C MP B", not "B MP".

Posted: 8/16/2003 5:26:58 PM EDT

[#18]

C MP= Chrome, Magneze Phosphate (Parkerized)...You got a good deal for a Colt upper. There should be a "C" on the upper by the forward assist if the upper is also Colt

[img]http://www.cavalryarms.com/barrel1.jpg[/img]
[url]http://www.cavalryarms.com/uppers.html[/url]

Posted: 8/16/2003 6:03:19 PM EDT

[#19]

Yep, it's a real Colt upper, that was the first thing I checked, lol. The barrel looks just like that, only it has a bayo lug, and it's fat under the handguards.

Posted: 8/16/2003 6:48:00 PM EDT

[#20]

Quoted:

No not an M4. I beleive most of the Colt Carbine models have M4 feed ramps these days.

Just make sure it has a chrome lined bore as well as the chamber. A lot of Colt models have chrome in the chambers only. If the bore is chrome lined it should also have "C MP B" on the barrel.

View Quote

Colt hasn't marked barrels with "CMP B" in 30 years. Originally in the 60's and 70's they were marked either "CMP C" or "CMP B"

All Colt barrels that are pre-ban (which this one is) are marked CMP and are chrome lined throughout.

Colt civilian post-ban barrels are NOT chrome lined in the bore, unless its an M4 barrel.

Any Colt upper marked with a "4" is an older M4 upper, all the current ones are marked "M4" above the clover.

EDIT: One more thing, "CMP" stands for "Colt, Magnetic Particle" which is like magnafluxing. It finds flaws in the metal that are invisible to the naked eye. It helps to insure you don't get stuck with a defective product. Except Colt and Bushmaster, most manufacturers skip doing this to cut costs.....

Posted: 8/17/2003 2:55:50 PM EDT

[#21]

Thanks all for the answers! Looks like I got a great deal on a great upper. I am very happy.

[ARCHIVED THREAD] - Is this an M4 upper?

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