The mini-gun is quite impracticable I mean they are REALLY heavy also they would chew up ammo so unless you had a constant supply of ammo you wouldn't last long with that.

It's for clearing out the big hordes. Otherwise, the magnum is perfectly adequate for popping some skulls, especially with how good a shot I am with one.
Know that I had also considered a flame thrower for my primary.

I dunno man if zombies would actually horde together.

If I wind up near some town, and the whole town is infected, an smg with a 30 round clip won't be too practical. An assault rifle is better, and extended clips can help as well, but the ability to not have to reload can be extremely useful. Just so long as you don't just open up with the thing like bullets grow on trees, you should be fine.

Again, a flamethrower would work too.