Complex sentence: It consists of a heavily modified Praga V3S 6 wheel drive truck chassis, armed with a twin 30 mm AA autocannon mounted on the rear for which the vehicle typically carries 900 rounds of ammunition, each gun being gravity fed from distinctive 50 round magazines.
Split into simpler sentences: It consists of a heavily modified Praga V3S 6 wheel drive truck chassis, coupled with a twin 30 millimeter autocannon mounting on the rear. The vehicle typically carries between 900 rounds of 30 millimeter ammunition, each gun being gravity fed from distinctive 50 round magazines.