hmmm. Now we're talking. Maybe I made the right decision after all.
If your lower is Glock mag it's plug and play. If Colt, there is a little work you need to do (file down the sides of the feed ramps, remove the ejector, and filed down the mag catch so the mags sit a little lower). Uses a standard AR BCG (modified a little for the RDB) and standard spring/H2 buffer. Much less reciprocating mass.