Really. The minigun’s low auto (50) is useless. Most targets need 2-3 hits.
There’s nothing really awful, especially while you’re inside a tank. A scorpion ballista deals the solid 300+ hp blows that are enough to obliterate just about anything. In fact, only the skeleton juggernauts need 2 hits. (I haven’t met jabberwocks).
The main point is that yes, you can use .50 machine gun, but why would you? Ammo with real gunpowder is precious, and there are plenty of ways to kill things using no gunpowder at all. Slingshot cannon, avalanche cannon and scorpion ballista are my choice. There are also guns shooting nail, rebar and serrated disks. All these things are easy to make and replenishable.