Are you setting up the dies properly? You said you were seating and crimping with the same die, not all dies do that (two and three die sets). When I have a choice I seat and crimp separately. I am not familiar with you dies but if your seater die has a screw in the top to adjust the bullet seating depth (OAL), this is how you do it. Put the case holder in the ram (if applies) then put a sized empty case in it and run it up. Screw your seater die down (with hand) tell it touches the case. Back the die off two turns and lock it down. Use the screw on top of the die to adjust seating depth (OAL). The die does not touch the case it only guides the bullet touching the bullet and seats the bullet. Use a separate crimp die.
I would try this before I went for a small base die. Let me say I don't use a small base die, but the looser you ammo is in the chamber you loose accuracy.