Here is the data from WOTC board:
1) The XM214 mini-minigun was developed in 1984 and closely resembles on the M134. Designed for helicopters & light aircraft, it fires 5.56mm rounds at variable rates of fire from 1,000 to 10,000 rpm. The gun and drive weigh 15kg and the driven variant uses 0.75 -> 3.2 hp dependent on the rate of fire. The gun can be powered by, (very heavy) NiCad batteries with a duration of 80,000 rounds at 1,000 rpm. Unfortunately the recoil force is 110kg at 10,000 rpm which would knock you off your feet, but (assuming a linear relationship) if the rof were 1,000 rpm (as limited by the battery pack) then the recoil should be only 11kg which might be manageable. Despite this, military tests with the XM214 proved the weapon far too impractical for man-portable use. In theory, one of these miniguns could be carried and fired by a single shooter at 1,000-2,000 rpm, if he could lift the gun + ammo + batteries (around 80 lbs). The effort needed to employ the weapon in such a manner is hardly worth it, and the lower fire rate eliminates the point of a minigun altogether.
2) The XM214 5.56mm Machine Gun was a terminated Research and Development project (1970-1971) for a six-barrel 5.56mm (.223 Cal.) Gatling type "mini-minigun". The XM214 was similar to the M134 "minigun" by General Electric Company (the same gun as the Air Force GAU-2B/A). It was electrically driven and could be installed on a pintle or in a turret mount. It was shown in a man-portable version in the movie Predator (1987) and in Jane's Weapon Systems of the same year there was an entry detailing the XM214. It had been tested by the Special Forces but rejected due to impractical weight. Availability today is extremely rare at best.
The weight of 45 lbs. is for the gun, motor, battery (good for 5,000 shots) and 500 shots. The gun, motor and battery weigh 15kg (33 lbs.). A tripod would weigh another 15 lbs. (+2 to Acc, but use the Gunner (Machine Gun) skill). One 500-round "cassette" weighs 14 lbs. The cassettes may be worn in a special harness ($100, 5 lbs.) on the back of the gunner and are linked through a rugged flexible chute to the gun. Two cassettes can clamp to the gun (or to the harness) at once, and it automatically switches when the first cassette is empty.
RoF can be set between 3-round bursts or 10,000 rounds per minute. Unfortunately the recoil force is 110kg (242 lbs.) at 10,000 rpm (GURPS RoF 166) which would knock you off your feet, but (assuming a linear relationship) if the RoF were 1,000 rpm (GURPS RoF 16) then the recoil should be only 11kg (24 lbs.) which might be manageable. Use 20-round groups for "Very High RoF" (p. HT78, CII66) to calculate "Hits in a burst" (p. B120).
3) The weapon takes 3 seconds [1 turn] to get it's barrel rotating at the proper rate, the weapon is then ready to fire. Because of the electrical operation the rate of fire vary from 300 to 6,000 rounds per minute [fire at least 15 bullets]. The recoil force generated is great but indistict, like a constant push, the weapon requires a Gyro or Vehicle Mount, without the character (even trolls) will fall down and the gun will most likely endanger unintended targets (GM's call). [The picture is a XM214, similar to the M134 but in 5.56mm not 7.62mm.]