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3/30/2008 1:00:38 PM EDT
I'm an obvious newbie.  What makes a rifle an M-4?
3/30/2008 1:22:35 PM EDT
[#1]
Easy way to point out M4s or M4geries cosmetically is by identifying the notch cut on the barrel. If you look on the M4 picture thread, look at the barrel past the front sight base.
3/30/2008 1:30:03 PM EDT
[#2]
It depends what you're asking for.

What defines a civilian M4gery?  A USGI M4 Carbine?  A Colt M4?

A USGI M4 Carbine is more or less:

14.5" 1/7 NATO barrel with M203 step cut and Gov't profile
"F" Marked FSB
A2 FH with either a crush washer or peel washer
side sling swivel
carbine length gas system
Delta Ring
extended feedramps in the barrel extension and upper receiver
A2 profile lower receiver
flattop upper receiver
small, round forward assist
SAFE/SEMI/BURST FCG
four position collapsible stock
castle nut
A2 pistol grip

These are the more or less generic features of an M4 Carbine, they're usually manufactured by Colt, and are marked as "M4 Carbine," though there have been some FN rebuilds documented.

HTH,
~Augee
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