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Gunsmithing Colt M-4 Upper on Knights SR-15 lower.

Re: Colt M-4 Upper on Knights SR-15 lower.

Copy that...was pretty sure on the HK, but Knights does weird stuff sometimes also. +each Mfc. often has their own castings with slight differences that aren't 100% if you mix/match. Anyone else have thoughts/input..
 
Re: Colt M-4 Upper on Knights SR-15 lower.

The KAC lowers (SR15 series) are all machined to mil spec as are their uppers.

The only place you will find anything different is with the E3 upper and that is only a difference in the bolt & barrel extension. Otherwise your good to go to mix match and swap upper and lowers to your hearts content.