So for some inexplicable reason, the animation files are in the base game but aren't used by the game/engine. Extracting them from the BSA file and installing them as loose files forces them to load. Thus the minigun should fire and behave as intended in 3rd person from now on.

Should be compatible with anything & everything. Install as per normal.

It just works.

Note: Both this and Minigun long wind-up (spin-up) restoration fix the aiming issues, but this doesn't change or alter the firing behavior.