[Fiberwyre_P2P]

I think the recoil damage on the flak might be a little crazy, though Godzilla's idea of it overheating, I do like.
(not to say that it should have unlimited ammo like the crizen.)

Or you could always nerf the actual stats of it.
Less damage
Slower rate of fire
A lot less spread
Shorter range
Make it not shoot over walls (In the Unreal Tournament games, it's essentially a shotgun, albeit a shotgun that has bullets that ricochet and can launch a flak grenade.)
etc.

(Even nerfing ALL of those aspects of it, it would still be better than the SD cannon. All I'm saying :P)