Any difference between a normal M4A1 receiver and Mk18 receiver? I mean it's the same gun but I'm just wondering if there is some kind of difference with the airsoft model. Could be ordering new lower and upper from eHobby Asia (at some point)
For added clarity, Mk18 is just the US Navy numbering system for the CQBR (close quarters battle receiver), you'll get more info searching for that than Mk18.