Sean,

I usually seat my bullets half way down, then rotate the cartridge in the station and seat the rest of the way down, maybe that will help. That is if you are using the correct (flat) seating stem in your seating die?

Most of the rounds in this batch did this. I was using the SWC seating stem and the bullets were sized correctly. I belled the mouth of the case just enough to accept the bullet. I think it looks like too much bell becuase the bullet has a large crimp groove and is crooked. I used the M die to bell becuase the RCBS was giving me lead shavings.

Do NOT use the Lyman M die. Do use the RCBS expander die. If that does not fix it, then u are seating the bullet crooked. Use the proper seating stem. Or the brass wall dia. is heaver then most brass and the rcbs die is also sizing smaller then needed for the dia of your bullet. I see it is a cast bullet, is the bullet sized to the correct diameter?