RAP - research armament prototype from RAI which was sold to Daisy then John Jovino/Iver Johnson which folded and remaining inventory went to Ultimate accuracy. After Daisy, Earl Redick went on to form Redick Arms Development (M91 etc)
RE MDT Metal mags
Bought one to try on Badger M2013 in a KRG chassis. The poly mags lock up correctly and feed as expected. Metal one doesn’t lock in and will not feed. I haven’t played around but not a drop in and go solution