the forend itself is not shorter but where the steel slides make contact with the stock it is milled out farther down. about 1 1/2 inches, which is why you get the slop. the shotgun itself is a regular adult 500. I am going to call mossberg again and see if i get the same answer. in the mean time i retrofitted a schedule 40 PVC coupler that works great as a spacer, just looks hillbillyish.