Did some math for the glory of it; how about...

+80% more Accurate
+45% faster Firing Speed
-25% less bullets per Ammo Point
-60% Damage
-45% Longer Spin-down time
-Cannot be Crit Boosted
*100% Minicrit boost
*Looses accuracy while firing for long durations, caps at -140%, accuracy reduction begins after 8 seconds and is reduced by 20% after every second past this.
*Regains Accuracy by keeping weapon spun up, accuracy returns to normal after 5 seconds.

This means that, no matter what range you're at, you'll always hit for 25 damage per bullet point. Stock Minigun maxes out at 520 damage per second at close range, but this does roughly half of that at ANY range.

Here's my math:

520 Base Dmg per second (Compared to Stock Minigun)
- 25% ammo used
+ 45% faster firing speed (Heavy fires 10 ammo points per second, sped up he fires 14.5
- 60% damage reduction
+ Minicrit Damage (35% on top of whatever damage dealt)

This levels it out to a solid 305 Damage per Second. A great weapon for slowing down oncoming pushes and great for making enemy Snipers have to bring their A+ game. Just barely kills a or Heavy at full health or a pocketed Soldier without a Battalion's Backup if you get the jump on them. Speaking of which, this thing balances out with the Battalion's Backup to have the effectiveness of a rapid-fire pea-shooter.

Sounds great @Voc, the Warrior. I was concerned it'd turn the heavy into a sniper at first but after reading the rest it seems pretty balanced. Kudos on the effort you put into the comment too.

Thanks for the contribution, I love the idea.