Confirm Action

Are you sure you wish to do this?

Confirm Cancel
Member Login

Site Notices
Posted: 10/1/2011 6:33:47 AM EST
I recently picked up a Colt A2 20" Rifle upper with 1/7 twist, non "F" front sight, "C" "AF" forged upper A2 receiver with a "4" above the gas tube port and M4 feed ramps on the barrel extenssion and receiver. I thought that M4 ramps were only on carbine length barrels? Maybe if it was an "F" marked FSB for a new A4.

What do you think I have here?
It appears to be all factory assembled and not a mixed together franken-upper.
Thinking a transitional piece from A2 to A4?


Link Posted: 10/1/2011 6:57:48 AM EST
You either have an early M4 upper receiver or a 6520 upper receiver to which someone mated a gov't profile Colt barrel to. It's not a factory assembled upper assembly.
Link Posted: 10/1/2011 6:59:12 AM EST
[Last Edit: 10/1/2011 7:02:00 AM EST by Frens]
those looks standard ramps on the barrel extension... but I could be wrong... M4 feed ramps on my colt carbine look a bit deeper.
the receiver could be a 6520 one.

colt put together some weird rifle/carbine in the past...

ETA: if I'm not mistaken BE with M4 feed ramps are marked with "4" on the right lug
Link Posted: 10/1/2011 7:50:23 AM EST
Lokks like the barrel extension has been modified.
Link Posted: 10/1/2011 9:28:28 AM EST
I agree with others here, looks like not a factory original.

My USGI M16A2 Colt upper half which the upper receiver is marked "C" and "M" (Colt / Martin Marietta), no "4" marking above the gas tube hole, no M4 feed ramps cut, barrel extension does not have a "4" at the 3 o'clock location and no M4 feed ramps.

Link Posted: 10/1/2011 11:07:02 AM EST
(Im not a colt expert) It does not look original but does appear to have m4 ramps.
Link Posted: 10/1/2011 3:27:01 PM EST
Thanks for everyones comments!

We know the receiver is factory M4 ramps since the handle has the 4 stamped under the anodizing. Certainly have seen some of those Colt receivers with ramps ground in after the anodizing with raw aluminium ramps. The extension clearly has some type of ramps deeper than rifle style but I dont see grinding/machining markings and the color on the ramps is the same as the rest of the extension.
The barrel is not dated. Does anyone know when Colt started dating their barrels?
The barrel ring is clean. It does not look like this thing has been apart or together recently. It is a clean older piece. I'm going to pull the barrel to do some refinishing so I will get a better look then.
The barrel extension ramps do not look like they were made at a later time as the discoloration/finish on the extension is uniform on the ramps and surrounding area.

I know the old saying is that if you can dream it up it probably was an option that came out of the factory at one point based on the volume that has been produced.

Link Posted: 10/2/2011 1:00:34 PM EST
[Last Edit: 10/2/2011 1:07:03 PM EST by Aimless]
Link Posted: 10/3/2011 5:19:20 AM EST
The flash hider is timed with a peel washer rather than a crush washer, so it's a relatively old barrel- without checking, I would say that the crush washer pre-dates *any* kind of extended feedramps, and there's no way that that's a factory configuration, as others have said.

Link Posted: 10/3/2011 5:45:03 AM EST
iirc my 6721 was done with a peel washer. aprox 2 months after the ban.
Link Posted: 10/3/2011 8:02:05 AM EST
Maybe the barrle extension ramps were factory modified thats why maybe it doesnt look modified could be something they did.It wouldnt be the first time in the old days anyway that Colt would sometimes build from what they had at the time...maybe its that.
Link Posted: 10/3/2011 12:51:20 PM EST
I did pull the barrel and I've got some more photos for you to review but have a theory so far. I think those that believe this is not a factory piece and was put together are correct. The barrel's exterior shows more wear than the upper which is relatively new.

It appears that the rifle sized ramps are slightly deeper then normal but certainly factory. Maybe the set up of the tooling, tolerance variation, etc.

I have since traded for a non-ramped Colt A2 upper and will return this upper to hopefully factory config. Also the replacement A2 upper is grey while this one currently is the newer black color.

I appreciate everyones feedback as it did help me get the forest out of the way of the trees!
I did not know that about the peel washer vs the crush!
I love this board!


Link Posted: 10/3/2011 2:19:27 PM EST
Originally Posted By Augee:
The flash hider is timed with a peel washer rather than a crush washer, so it's a relatively old barrel- without checking, I would say that the crush washer pre-dates *any* kind of extended feedramps, and there's no way that that's a factory configuration, as others have said.


All the 80s and early 90s era pre-M4 700 series carbines and early M4s used peel washers and they had the extended feedramps and M4 feedramps. According to the USGI Colt Carbine Parts Variation Guide tacked in the Retro Forum, the crush washer was introduced circa 2000. For instance, I've got a late 90s/early 2000s Colt 733 upper with A1 sights and case deflector, marked M4, with M4 feedamps, and it has a peel washer.


Just by eyeballing the pics, the extension on that barrel appears to be the slightly shallower, pre-M4 extended carbine ramps. My guess would be someone wanted M4 feedramps on their rifle really bad so they had that extension installed on that barrel to mate it up with that receiver.

OP, any good pics of the index pin and where the extension mates to the actual barrel?
Link Posted: 10/3/2011 3:25:01 PM EST
[Last Edit: 10/3/2011 3:25:01 PM EST by Lancelot]
Topic Moved
Link Posted: 10/3/2011 4:56:15 PM EST

FSB also has the "C" and symbol.

Top Top