I believe the one used in the movies is the GE XM214 Microgun in 5.56 Nato. A six barrel gun, it's appropriately nicknamed the, "Six-Pax". The Six-Pax has been mounted on vehicles, aircraft and riverine boats (I had a friend who actually used one and it quiets ambushes muy pronto).
Per George Chinn (Vol 5, The Machine Gun), the basic gun weights 25.5 lbs, drive motor 7.5 lbs, feeder 3 lbs. When loaded with 1,000 rounds of .223, it weighs 85 lbs. It is 27 inches long and has a variable feed rate of fixed rates of fire from 400 to 10,000 SPM (1000, 6,000, 10,000 spm are available). It requires .75 HP for 2000 spm (shots per minute), 1.5 HP at 6K spm, and 3.2 HP at 10k spm. Barrel life is 100K rounds.
Every American should have one.
------------------
Vigilantibus et non dormientibus jura subveniunt