This was recorded on a selfie stick held between my knees with a mounted phone camera pointed at a mini TV screen. Apologies for the very bad quality. Also there is no audio because of external recording. :/
This weapon can be found in the mission "The Gates of El Presidio". Head through the gates and up the ladder directly to the right. Try not to get shot too much as there are a ton of enemies in here.
Quality might be bad but hopefully this gets the job done. Didn't have a PS3 screen recorder so I have to work with what I have. Enjoy! :D