I have a 12 gauge Wingmaster 870 Magnum ( has a 3in ejector because the S/N ends with an M) that has "12 Gauge Magnum for 3 in shell" stamped on the barrel. Will this reciever/barrel combo shoot 2 3/4 in shells too? Everytime I shoot a 2 3/4 in shell it is not properly ejected.. 3 in shell eject perfectly.. I have this gun for years and it has done this since i purchased it new in the 1980's..Never worried about it before cause I always shot 3 in shells..