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Posted: 12/23/2005 10:09:52 AM EDT
A barrel with M4 extension installed in a non-feedramp cut upper?

Here's why I ask. I recently bought a used Colt which has a 1/7 M4 profile barrel (C MP marked). The upper receiver isn't marked but I believe it's a Bushy. Anyway, it's hard for me to tell if the barrel extension is an M4 or not. The receiver definitly isn't though. It appears as if everything would function correctly, and the previous owner said it ran like a champ.

I remember a month ago or so a topic on the matter with some good pics, but I can't find that topic for some reason.
Link Posted: 12/23/2005 10:51:27 AM EDT
Tagged, I'll take a pic for you Seth if someone doesn't already have one to post. BTW, I would think it should run fine that way, if the bullet hits the ramp as it should it would feed ok. If it hits the receiver you're no worse off than with a standard extension barrel.
Link Posted: 12/23/2005 11:43:06 AM EDT
[Last Edit: 12/23/2005 11:45:32 AM EDT by M4Madness]
I don't have a pic, but you should have no problems with an M4 barrel extension mated with a non-M4 upper receiver.

Problems arise when you go the opposite route - non-M4 barrel extension with an M4 upper - due to the fact that a "wall" exists where the M4 ramps on an M4 upper meet the regular feed ramps on a non-M4 barrel extension.
Link Posted: 12/23/2005 12:30:30 PM EDT
Thanks guys!

I guess I should've just asked this. Do all Colt M4 barrels have the proper M4 feedramps on the extension? I know some companies make them both ways. I have no idea if Colt does.
Link Posted: 12/23/2005 1:19:35 PM EDT

Originally Posted By Seth_Livzz:
Thanks guys!

I guess I should've just asked this. Do all Colt M4 barrels have the proper M4 feedramps on the extension? I know some companies make them both ways. I have no idea if Colt does.



I would assume that all Colt M4 barrels have the M4 feed ramps as well. I'm not sure of the ramps' inception date, but it would probably be a safe bet that all of them do.
Link Posted: 12/23/2005 1:23:18 PM EDT
[Last Edit: 12/23/2005 1:23:28 PM EDT by BravoCompanyUSA]
Link Posted: 12/23/2005 1:49:22 PM EDT
No date on it anywhere. It's simply marked:

C MP
5.56 NATO 1/7

It probably does have the M4 extension on it. But I didn't know if Colt made some different configs like a lot of the barrel makers do nowadays.

I think my question has been answered. Thanks all!
Link Posted: 12/23/2005 2:04:26 PM EDT
Link Posted: 12/23/2005 2:07:14 PM EDT
Colt M4 barrel extensions have a "4" stamped on the right edge (looking straight ahead into the chamber). You might have to clean it well to see it.
Link Posted: 12/23/2005 2:10:02 PM EDT

Originally Posted By Kisara:
Colt M4 barrel extensions have a "4" stamped on the right edge (looking straight ahead into the chamber). You might have to clean it well to see it.





"4" near the ejection port
Link Posted: 12/23/2005 2:10:13 PM EDT
Link Posted: 12/23/2005 2:25:37 PM EDT
That's exactly what I needed! Thanks!

There's no 4 on my extension, and after looking at that archived link I am positive I have a rifle extension.

Looks as if I have a mixmaster stechild barrel
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