A recoiless gun?

[Robby Foxfur]

this is amazing i have seen this gun and the idea behind is is really really impressive, to counter the fact that the expansion of gas from the bullet that pushes the gun up or rather back. to counter this improves accuracy by a huge amount for multiple shots in a rapid order.

 

[Mortons4ck]

Auto-Assault 12 Combat Shotgun. Low maintenance, low recoil.

Spoiler

5 foot 99 pound shooter [http://www.youtube.com/watch?v=7zlWplfLQ2E&feature=related]
One-handed [http://www.youtube.com/watch?v=siOEEOTjGqM&feature=related]

It also costs more than a helicopter.
So if the time ever came where you needed to buckshot 90 people a minute, your money would have been better spent elsewhere.

More than a helicopter?? Well it is still in the prototype stages (10 working models I believe), so I'm assuming the price tag you're quoting is factoring in the Research & Development as well as the machinery to manufacture it. If it ever saw mass production, I'm sure each unit would be much cheaper (than a helicopter at least) and the fixed costs more evenly spread.