Mag release is from Valkyrie Tactical, they call it a skull mag release. To me it looks more like a Zombie They are out of stock right now.
KAC parts other than the lower and triggerguard are the rail covers, the M4 RAS, the 600m rear buis, I also have 1 more KAC 2 stage match trigger that I'll probably install.
The upper on it right now is a Colt 6731 that had the barrel cut back and a permanet FH attached. It is a 1/9 twist postban version of the 6721 upper.
So I guess this is a KAColt carbine