i also have an M4 on mine and love it....also my buddy had an M4 on his f4i and it sounded greatbrentsR6 said:
i also have an M4 on mine and love it....also my buddy had an M4 on his f4i and it sounded greatbrentsR6 said:i had a carbon M4 full system on my R6 and loved it. a bit on the loud side but it was an R6. check the M4 out.