How to Identify a Colt M4 receiver?

I bought a Colt flattop upper receiver stamped with “C AF” for my H-BAR. It also has the number '4' stamped just above gas tube hole on the receiver. Can anybody tell me if this is a M4 receiver? How can I tell if it has the M4 feed ramp? Thanks for your help.

# I bought a Colt flattop upper receiver stamped with 'C AF' for my H-BAR. It # also has the number '4' stamped just above gas tube hole on the receiver. # Can anybody tell me if this is a M4 receiver? How can I tell if it has the # M4 feed ramp? Thanks for your help. # # Dave #

A M-4 upper would have a 14.5' barrel, bayonet lug, birdcage flash hider and a variety of other features that can be found in some detail on the Colt web page under the military weapons portion of their site. If you purchased a receiver and didn't have to do the requisite BATFE NFA paperwork, either you or the seller has made a big mistake. Odds are, you have a civilian legal M-4 lookalike with a 16' barrel. If not, get the receiver out of your house as mere possession of the receiver with a lower means you have an unregistered short barrelled rifle, which is a big no-no.

bzzt, try again. The upper receiver can be an M4 or pre-M4 without any effect on the lower. You're confusing the 'upper receiver' with the entire 'upper', and the SBR issue with the question about feed ramps.

Glenn

# # A M-4 upper would have a 14.5' barrel, bayonet lug, birdcage flash hider # and a variety of other features that can be found in some detail on the Colt # web page under the military weapons portion of their site. If you purchased # a receiver and didn't have to do the requisite BATFE NFA paperwork, either # you or the seller has made a big mistake. Odds are, you have a civilian # legal M-4 lookalike with a 16' barrel. If not, get the receiver out of your # house as mere possession of the receiver with a lower means you have an # unregistered short barrelled rifle, which is a big no-no.

I know that the upper receiver assembly I bought is a pre-ban A3 Colt flattop with 16 inch H-BAR. I bought it for my pre-ban 6600 Colt H-Bar lower receiver. But I'm not sure what distinguishes a M4 flattop upper receiver from a non-M4 flattop. Is it the feed ramp? If so, how is it identified? The upper receiver that I bought has a '4' stamped above the gas tube. Does this mean anything? Thanks for your help.

Dave

> ... entire > ... either > ...

double - bzzzt

if you have an upper receiver (of any year manufacture) with a barrel length of under 16' and a lower receiver (of any year manufacture) and you have not paid the NFA tax for a Short Barrelled Rifle (or the lower is a registered machinegun), you are in violation of the NFA laws. the length of the barrel on the upper most certainly has legal implications when used with a lower.

as an aside, if you don't own an AR-variant or an AR lower receiver, you can purchase all the uppers in any length you want. only when an upper and lower are together, or in close proximity, (and hence a firearm) does the law take affect.

i have no idea what the feed ramp has to do with any of this.

andy b.

On Sun, 29 Jun 2003 22:14:42 +0000 (UTC), 'Glenn R.'

bzzt, try again. The upper receiver can be an M4 or pre-M4 without any effect on the lower. You're confusing the 'upper receiver' with the entire 'upper', and the SBR issue with the question about feed ramps.

Glenn

> ... flash hider > ... the Colt > ... purchased > ... either > ... civilian > ... of your > ... an > ...

> ...

Boy, lots of good info here - not. Post this question at www.ar15.com/forums Maybe you'll get a better answer than the machinegun bedwetters have to offer.

Triple Bzzzt. Here's where you may be confused (and where I did a lousy job of trying to explain the first time);

The question was about the feed ramp in an M4 upper receiver, and how to tell whether it was an M4 receiver. If I understand the question, it's NOT about a complete M4 upper. Just the upper *receiver*, the thing that holds the barrel and sits on top of the lower receiver. Barrel length is irrelevant, in the question of identifying an M4 upper *receiver*.

Here's the info about how to identify an M4 receiver: http://www.biggerhammer.net/ar15/uppers/

I've seen side-by-side pictures on the 'net showing the difference visually. Maybe at the Maryland AR site?

Glenn R.

# double - bzzzt # # if you have an upper receiver (of any year manufacture) with a barrel # length of under 16' and a lower receiver (of any year manufacture) and # you have not paid the NFA tax for a Short Barrelled Rifle (or the # lower is a registered machinegun), you are in violation of the NFA # laws. the length of the barrel on the upper most certainly has legal # implications when used with a lower. # # as an aside, if you don't own an AR-variant or an AR lower receiver, # you can purchase all the uppers in any length you want. only when an # upper and lower are together, or in close proximity, (and hence a # firearm) does the law take affect. # # i have no idea what the feed ramp has to do with any of this. # # andy b. # # # # # On Sun, 29 Jun 2003 22:14:42 +0000 (UTC), 'Glenn R.' # # bzzt, try again. The upper receiver can be an M4 or pre-M4 without # any # effect on the lower. You're confusing the 'upper receiver' with the # entire # 'upper', and the SBR issue with the question about feed ramps. # # Glenn

Glenn, Thanks for the web site. The information was useful. Dave

> ... job > ... NOT > ... holds > ... visually. > ...