TX-12 Underbarrel Shotgun Posted January 28, 2012 in Rifles, Shotguns by Steve Johnson with 52 CommentsTags: rifle, rifles, shotgun, shotguns Ten-X Tactical has developed a lightweight underbarrel shotgun for M4/AR-15 firearms. It can either attached to a underbarrel picatinny rail, or it can replace the bottom half of an M4 handguard. 7.5″ barrel model TX-12 with 10.5″ barrel Win a Kel-Tec PMR-30 !!!