Its a drop, it's pretty rare in my experience, it's something like it can drop from any burner (I THINK) it was, when they drop a sniper rifle it has a less then one percent chance to be that gun. Honestly imo it's worth it, i love mine... i got this info from the wiki awhile ago.
HOW THE F#$% DID YOU DO THAT!? That was quite possibly the coolest thing I have ever seen. Sorry for thread jacking btw, you get the Cobra from Burner enemies, primarily found in the Beatdown area of Torgue DLC --- GT: MasterKush814
Its an engine built around a search engine called "let me google that for you" aka LMGTFK it is used to point users to the answer by using google (when the person asked the question could have used themselves) in a smug manor.
Its quite funny at times, in my opinion. --- XBL GT/PSN: Tsuruke.