Just looking to find out what magazines will actually work in the RPR.
What have you tried that worked / what did NOT work.

Any DPMS pattern should work but won't necessarily give you long enough OAL depending on your load.  ASC mags have a long OAL but quality is hit and miss.  I bought 4 and only 1 would lock in consistently.

AICS compatible mags will work and will give a longer OAL.  I just bought a 10 round Magpul AICS mag and it works great.  Plenty of room for me to load my .243 with 107 match kings and hit the lands, and it feeds incredibly smooth.  I will be buying more.  Can't beat it for the price.

I've tried the Magpul 10rd thru 25rd LR/SR, Lancer 20rd  L7 AWM, Accurate Mag 5rd and 10rd, Alpha Industries 10rd. The Alpha, because of its double stack single feed design is tight going into the mag well. Besides that it functions like all the others I've tried.

All mags I've tried have worked. I've tried Magpul, DPMS, and M14.

308 magpul magazines work (normal or aics), MDT mags work

Accurate Aics pattern mags. Magpul aics pattern. PMAGs