Sorry but IRL things are great basis for sourcing new inspiration from.

BTW Science fiction requires a dash of IRL.

Unlike Science Fantasy which does not.

1. People can't carry a Minigun and fire them and have full use of their arms afterwards. It was considered a feat when someone fired a .50 Caliber Machine Gun in WW2 unassisted.

2. Tanks are fully destructible.

The HMG is not a minigun.

Has more common to size to this thing with a smaller drum (current drum is for 2k rounds)
http://upload.wikimedia.org/wikipedia/commons/4/44/M61_Vulcan.jpg

Why would a technically advanced civilization use a pneumatically or hydraulically driven device?

the HMG is a minigun, and a minigun is a gattling gun with an electric motor not hand cranked.

One barrel is fired at a time, is accurate, does use a 7.62-.30mm, and is used because it aircools.

RL is a bulwark against stupidity.

PS: a rail gun does not recoil, the US NAVAL ACADEMY-WEAPONS DESIGN OFFICE has a 94pg PDF that you should read.

Why would a technically advanced civilization use a pneumatically or hydraulically driven device?

the HMG is a minigun, and a minigun is a gattling gun with an electric motor not hand cranked.

One barrel is fired at a time, is accurate, does use a 7.62-.30mm, and is used because it aircools.

RL is a bulwark against stupidity.

PS: a rail gun does not recoil, the US NAVAL ACADEMY-WEAPONS DESIGN OFFICE has a 94pg PDF that you should read.

for example: 73 Easting...you are such an idiot.

Tanks in real life are far from un-killable.

That aside, I believe that RL situations does need to be applied to certain areas (ie, we should still be affected by gravity) but at the same time using RL situations to guage how powerful an item should be is terrible (see: 80GJ Turrets).

Current American military tech can reliably disable a T-72 tank. I'm sure there have been advances in tank tech that we do t know about.

To educate on "killing tanks..."

There are 3 kinds of tank kills. A turret kill, a mobility kill, and a catastrophic kill. Turret kill means you've destroyed the main turret, but this does nothing to stop the tanks other weapons, or have the tank crew hop out and kill you, or simply run the infantry over (tank crews refer to infantry as crunches for a reason) Mobility kill means you've destroyed the tanks ability to move. Of course, it can still blast the bejeezus out of you with the main turret, and the tank crew can dismount and kill you still. A catastrophic kill means you've utterly destroyed the tanks ability to function, period. If you hit the ammunition stores and detonate them inside the tank, or drop a specialized tank busting bomb on them, or in some way make the tank not worth its weight in scrap metal. For the record, there are plenty of videos on the internet of M-1 Abrams hitting anti-tank mines and being flipped perpendicular to the ground (tank is basically point straight in the air balancing on its ass end) landing back on the treads and driving off.

So yes, they are not unkillable, but you either have some damn good explosives or be a damn good shot and hit the munitions. They are not to be taken lightly, in any case.