That's an German MP-40. Don't think it's a one-off, given that the Nazis made over a million of them before they got out of the business in 1945.
Google it for lots of images and history.
Don't know why the barrel is in the white, but the barrel profile, including the hook on the bottom of the muzzle, seem to be standard.
"The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza
Baby Jesus cries when the fat redneck doesn't have military-grade firepower.