A couple of years ago I built a MK12 Mod 1 SPR Type Rifle using the following parts:
RRA Lower with all Colt small parts including an A2/A4 Rifle Stock
Geissele SSA-E Trigger
LaRue "Stealth" Complete Upper that LaRue built with an 18" Lothar Walther Barrel, 1 in 8 twist, Wylde Chambered.
The...