The minigun is Blain's weapon of choice in the flick, and Ventura gets to look like a total badass wielding it for a couple scenes before the barrel-chested character gets taken down by the Predator. Mac then picks up the gun and — in a blind rage — just completely empties the thing into the jungle after the fleeing alien. The gun's spinning, six-barreled muzzle looks absolutely terrifying onscreen, and, as the rest of the team joins Mac in lighting up the forest, they may as well be firing BB guns compared to its sheer volume of hot lead. It's a great scene, and it's pure Hollywood — mainly because using the minigun in that manner would in no way be possible in real life.
First and foremost, the M134 is designed for use as a mounted weapon. As pointed out by ScreenRant, it requires an external power source and separate box for ammo, and when complete, the rig is far too heavy for anyone — not even Jesse Ventura in 1987 — to lug through the jungle. Also, even with its firing rate substantially slowed down — which had to be done in order to look right on camera — the gun would blow through a ridiculous 1,200 rounds per minute, meaning that Mac's jungle-blasting fest should only have gone on for a few seconds, rather than the minute or so depicted in the movie.
Consider too that like most guns, the M134 ejects shell casings as it fires. Taking into account the insane volume of bullets fired by Mac — and even if all those bullets were magically coming out of nowhere, since he had no ammo box (read: Bag of Holding trope) — he should have had a piping hot pile of them up to his knees by the end of his little rampage, but instead, there was nary a casing to be seen on the ground.
