There's something wrong with your barrels...
Alright, here's my RVT-9FC sub-machine gun. It uses conventional 9mm rounds, and can empty it's 20 round clip in five seconds. It's a completely custom design, using different parts, none from the same gun. it has a built in laser sight, and it's barrel extends the whole way down the gun, thanks to the aft-mounted ammo container. This gives it unparalleled accuracy in it's class, and it gives it perfect balance for ease of carrying.
Also seen in the picture, it's customizable. for ammo containers, there's the traditional 20 round clip, then there's a 40 round extended clip. Then, if you absolutely must kill everything in the room, it has support for belt fed guns, with it's 100 round drum clip.
The flashlight is a small Maglite, for durability and peace of mind. The silencer makes the gun but a mere whisper. (Actually, it makes it about as loud as a .22.) The scope is a x4 zoom for sniping, which this thing can do, thanks to it's incredible accuracy.
And for reference, here's the fully modded gun.