This article is from the The Terminator FAQ, by Karsten A. Loepelmann kloepel@connect.ab.ca with numerous contributions by others.
From <tighe@convex.com>:
It appeared that the weapon Arnold had in T2 was a General Electric
minigun, M-134/GAU-2b. It fires a 7.62 mm round from 6 rotating barrels
at peak cyclic rates of up to 6,000 rpm. Barrel rotation is
powered by an electric motor. The "ammo chain" is actually an
enclosed feeder. The bullets are inside of this feeder. That is
why it appears to not move. If you look closely, you'll see a
steady stream of spent cartridges dropping out of the bottom of
the weapon.
 
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