It’s an anti-tank rifle cut down to a pistol. The grip is designed in such a way that it easily flies out of the shooter’s hand and backwards several meters, as attempting to actually hang on to the thing will result in wrist and tendon injury. It’s single shot, because a second shot is unnecessary, which is good, because the shooter is unlikely to ever agree to fire the thing second time.
I posted this because I am in bed giggling uncontrollably at the thought of this.
Whiskey may have been (was) involved in the thought process.