H&K 91 This particular example has two interesting accessories. It has the H&K heavy bipod and what appears to be a South African 30 round straight magazine. The heavy bipod clamps onto the receiver channels and is only compatible if a slim style handguard is used. As for the magazine, most G3 30 round magazines are two mags welded together. The South African model is a single piece although cheap U.S knockoffs exist.