This is a gun that's a foot long and weighs 45 kg. That alone should set off alarm bells. That's a hell of a heavy gun at less than the length of your forearm.
2000 round capacity. Also, "barrel" drum magazines wouldn't do it. Belt fed? Fine. But the weight is still an issue. A 20mm slug weighs 3.5 oz. 2000 of them weighs 437.5 pounds. That's heavy, no matter what sort of powered armor you're wearing. And it takes up 52464.5 cc of volume. That's almost 2 cubic feet. Takes up too much room. And besides, at 100 rounds a second, 2000 rounds of ammo's gonna last you 20 seconds. Also, 100 rounds a second is fast for a handheld anything. It sounds like you tried to scale down a vulcan cannon. That's just not feasable for an anti-personnel weapon.
Also, the range on that thing is a bit ludicrous. Anything that can throw a projectile six clicks is gonna have a hell of a lot of recoil. Just mentioning.
That's my two cents.