seems that the two were not made to work together.I have some trick inserts for the mag well that will let the gun except colt 9mm mags.seems the bottom of the bolt that cocks the hammer is of a differnt angle and cuts into the hammer face.have been trying to meet up with a fed that carrys a colt sub in 9mm.but no luck yet.everyone around here seems to use the mp-5 in 10mm are the m-4 in .223
any one know anything about the lower being differnt on the .223 colt vs the 9mm lower colt??
