cbx yes the GI mags such as Center Ind., Sanchez,Parsons, Cooper,Precision, Adventureline ect. are goverment contract mags. Also some mags such as Labelle made mags for Bushmaster and DPMS. On the 30rnd. GI mags check for cracked and bent feed lips, the green anti tilt followers are also a plus. Make sure you look at the date of manufacture on the mag so you don't get stuck with a Post Ban restricted mag.I see used GI mags at shows around me for $10.00-20.00 ea. Myself I've found the GI 20 rnd. mags with alloy followers to be more dependable in the feed and function. The 20's are better for bench work also.