you may have a couple small issues like getting the body pins to line up. the rear one will not go in for me so I just left it out.
the other thing that might cause a problem could be the position of the mag release. if it doesn't fit, just try a different one. I put a JG box in CA M4 body and the CA mag release wouldn't fit right. mags could not be inserted or released properly. I threw in a stock TM one and it was fine.