You do not need a small base die in most cases. You do need either a Hornady case comparator or an LEvWilson case gauge. This is to set the shoulder back. Unlike bolt actions you need to set the shoulder back to SAAMI minimum. The reason is for function. Check your die setup each time and every 50 rounds or so. Make certain you remove the primer crimp from each case and there are commercial cases that have crimped primers now. Seat the primers flush or below, use CCI 450, CCI 41, Rem 7 1/2, or Win SR primers only. A good starting load to try is 25.5 Win 748 and a 55 grain bullet or 24.5 IMR 4895. Seat to 2.250-2.255. You do not normally need to crimp. The picture is 4000 rounds of training ammo loaded a couple of years ago for my ARs.