M4 Cuts > General Discussions

Posted: 8/12/2007 4:56:42 PM EDT

This might be a idiotic questions but I'm new to the whole "what kind of cuts" different ARs have. Anyway, I have a RRA LAR-15 M4 and I was curious to know how you tell? I just ordered a new flat top upper with M4 cuts and I was assuming at the time I made the right choice. Someone please help me out!

Thanks!
T

Posted: 8/12/2007 9:31:20 PM EDT

[#1]

anyone?

Posted: 8/13/2007 6:36:49 AM EDT

[#2]

We don't use the "M4" cuts. We use standard barrel extensions and extend the ramps into the receiver, breaking the square edge and improving feed with a variety of ammo.
Steve/RRA

Posted: 8/13/2007 3:52:13 PM EDT

[#3]

Ok, so the standard barrel extensions on a RRA 16" barrel can be used with an M4 cut upper reciever?

Posted: 8/14/2007 4:53:25 AM EDT

[#4]

The ramps won't match up (std bbl extension to M4 cut upper)unless you extend them into the receiver.
Steve/RRA

Posted: 8/14/2007 6:36:46 AM EDT

[#5]

Ok, I see. So is that something that can be taken care of without the need of a gunsmith?

Posted: 8/14/2007 7:32:46 AM EDT

[#6]

Only if you;'re willing to extend the feed ramps from the extension over/through the M4 ramps in the upper...which should work.
Steve/RRA

Posted: 8/14/2007 12:54:09 PM EDT

[#7]

Is it recommended to extend the feed rams by filing them or should I just return my stripped upper for the right one? I am capable of extending the feed ramps by filing them but I want to make sure it is as easy as I think it might be? By filing I should make sure both surfaces are smooth right?

Posted: 8/15/2007 4:47:08 AM EDT

[#8]

I would go the different upper route, and then extend the ramops from the extension into it with a rotary grinder rather than gamble on the M4-cut upper working the way you want it to.
Steve/RRA

Posted: 8/18/2007 12:43:07 AM EDT

[#9]

Can I ask as to why RRA doesn't just put in STANDARD M4 ramps? It would be good for EVERYONE. LMT does it, why can't RRA?

Posted: 8/20/2007 5:14:49 AM EDT

[#10]

Because what we do works on all of our .223 configurations.
M4 cuts were an afterthought by Colt for their later select-fire M4 carbines. It isn't standard on all of their production guns. LMT runs with a very limited variety of upper/barrel combinations, and standardizing to the M4 ramps/extensions, uppers probably made sense to them for their applications.
Steve/RRA

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