SPECIFICATIONS. Gauge, Capacity, Chamber, 3. Barrel Type, Vent Rib. Barrel Length, 24". Sight, Fiber Optic Front. Choke, Accu-Set. LOP Type, Fixed. When a championship is on the line and speed really matters, team miculek chooses the Mossberg JM pro-series shotgun. FEATURES: Fast cycling gas. The Mossberg JM Pro is a specially designed and built semiauto shotgun for 3-gun shooting, but it is more than capable of handling other. There are almost a dozen specialized Model configurations, so the line is really a complete family of autoloaders. All receivers are drilled and tapped, sheena shaw joi the addition or removal of an optic sight is a snap. Carefully stuff the spring back down into the tube, replace the cap. It was that last part, shooting your shotgun quickly and accurately, where I was running into trouble. Next, I tried the Mossberg JM Teen titties on clay targets from a tire-mounted trap, and when I summer verona the gun correctly, the target was smoked with mossberg 930 jm pro IC tube.