Pretty sure its not pump-action. There's another clip of one of the characters using it shortly after the first shot of it. You can see the barrel of it, and it seems identical to the Olympia. Mainly the rails being the most defining feature.
Whoever said 'nothing's impossible' never tried nailing Jell-O to a tree.
IDK what you're smoking, the Olympia was great in MP.
Great? I'll be nice and say the gun was sub-par. It was sweet in SnD where you got 6 enemies with no respawns, but outside of that gametype I found it to be very lacking. Can't shoot fast enough to handle a regular flow of enemies. Boy did I love getting a two-piece with it though.