I wanted to share my experience ACTUALLY needing a Small Base die. I have been attempting to reload 762x39 on my 1050 autodrive. Tried as much as I could to get my Lee sizing die to a position that would shape the case to pass my cartridge check, but no avail. The case would get suck just before the rim, and as I adjusted the die lower eventually it would cause the autodrive to jam.
Luckily my local bass pro had a 762x39 Small Base die in-stock, so I quickly picked it up and got it installed in the toolhead. Lo ad behold the cases pass the cartridge gauge flawlessly. On to the next step, setting up the toolhead for flare (lyman m die), powder, bullet placement, seat, crimp.