COLT 6943 VS 6945 FOR DUMMIES

I plan to do a adjustable block on mine someday but even being a little overgassed suppressed its not likely tearing my brass or moving parts up all that more than unsuppressed.Good news, MK18 upper arrived right now from Principal Arms.  Seems to be fantastic.  I want to finalize the remaining parts I ought to get to complete this Make and reap