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AR15.COM
AR Sponsor
5/1/2004 5:02:13 PM EDT
is there a difference between a m16 upper and a ar15 upper???  if yes, whats the easiest way to tell the difference?
5/1/2004 8:16:34 PM EDT
[#1]
Generally, no, and an M16 upper will work just fine on an AR-15.

Early Colt uppers, and some aftermarket uppers lack the "sear relief cut" which means that while they'll fit on an M16 (pin sizes may require an offset pin or adapter), but won't functon in full auto without the cut.
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