In loading for 4 BLRs over many years, I have never had to resort to small based dies. BLR chambers are usually cut to more minimum dimensions though. Be sure to keep brass trimmed. Carefully set your full length die so that the sized case will just enter the chamber fully with only finger pressure.
Regarding powders-for smooth operation the BLR likes powders toward the slower end of the burn rate chart for that cartridge. For example, the .308s would prefer 4064, Varget and RL15 over 3031 and 4895.