The birth of an abomination

Late one night, Mr Fletcher had had a few too many whiskeys, and was not in a clear state of mind, yet he pushed through in designing a new weapon even in his current state. What he designed though was not what many would call... good. The design was based on his own automatic revolver, but in a carbine form.

Fletcher Revolving Carbine:
Calibre: .455 Bentall/.44 Magnum
Magazine capacity: 6
Loading type: Break action carbine... thing
Action: Double action recoil operated semi-automatic carbine
Sight type: Blade and Leaf adjustable up to 300m
Weight: 3.1 kg
Muzzle Velocity: 260 m/s / 400 m/s
Effective range: 300m
Maximum range: 600m / 1000m