User blog comment:Redkite/Two New Ideas/@comment-1476628-20120630045332/@comment-1476628-20120630053259

http://www.youtube.com/watch?v=wapDDxuvhCg&feature=plcp

At 1:13


 * The barrel is shorter


 * The thing has a 20 round magazine


 * its has the Engineer first person


 * And for the last part (THE GUY FIRED A SMAW BEFORE)