Hey, i found out this glitch/bug while scrolling with my mouse, i got a logitec 6500, it got a unhinged scroll, so i can just turn the wheel and it keeps on scrolling, anyways back to the subject, what i did was scroll my mouse with the B23R gun, and fired and when you do that it will become a Machine Pistol, the aim is not that easy to hit with, but it's just as effective as an Submachinegun at close quarter combat, and it's a nice little showoff if you aim to get on killcams.
I will post a little video of this later.