I have been eyeing the rcbs AR dies and it seems beneficial. I think they may taper crimp the case. And also partially resize the case rather than fully resize or neck size allowing the round to cycle properly from differences in case length where performing in a semi auto wouldn't work as fluidly. I havnt done a whole lot of reloading but I think the decapping resizing die is one die and bullet seating is another. These AR dies are a two die set. Im trying to maintain consistancy in my reloading and was leaning toward a micrometer type bullet seating die also by rcbs. Just trying to be as accurate as possible thoug I understand there's alot more factors to consider. This is for. 223 caliber in a dpms bull twenty. Not necessarily for running in the acr.