[2raiderace1]

I have a Green Label Colt AR15 with an M4A1 14.5" barrel Knights RIS upper. I got the upper from a Colt employee who told me it was from the 1st run for Spec Ops/ CIA going into the Middle East back then. My question is will an H&K 416C 10.5" Barrel fit directly onto the Colt Green Label ( no sear block ) SEAR lower? From what I read on some of the post I think the answer is yes but I want to make sure. I also have a Colt SEAR gun in 9mm 10.5" barrel and am able to switch my registered SEAR from .223 Colt to the 9 MM Colt and they both work fine. If anyone can verify that the 416C will switch out to the H&K upper I would really appreciate it. Thanks...

 

[JoshNC]

Green label Colts have a large front takedown pin, so a milspec upper with the standard front takedown pin hole will not work without an offset adapter. This includes the hk416 upper. I suspect since you're already using what is undoubtedly a milspec Colt upper, you must be doing so with the use of an offset adapter. These offset adapters have a nasty habit of rotating and causing issues. If you have a registered AR15 DIAS I would buy a low rear shelf lower and use the sear in it with a 416 upper.

 

[nsheers]

Just to clarify, an HK416C has a 9 inch barrel and a proprietary BCG and buffer/spring, which presents separate challenges for fitment. I suspect the OP is referring to the basic 416 upper in the 10.4 inch version rather than the 416C.