MDM, Just to add a little bit to what the other guys are telling you... All of the new short actions are the 4.4 screw spacing. Accutrigger or no accutriger. The higher end rifles got a design change where the trigger sear, trigger gaurd, action(flat on right side for the bolt release, is not present) is different. The stocks have some minor inlet differences as well as the thickness of some of the DBM mounting ears. I believe that for most people that like to change barrels and customize their rifles, the tried and true side bolt release is the most popular action to work with.