Another thing to consider is whether you on the edge of or do have compressed powder scenario. I had a similar issue with a large case capacity cartridge and slow burning powder being used. I sent dies back to manufacturers, had custom seating stems made, bought new dies and a few other things. For my situation, it boiled down down to the extra force of the bullet trying to compress the powder would cause the bullet run out to be inconsistent. After literally spending a couple MONTHS chasing this issue, a friend of mine that shoots long range black powder rifles recommended a LONG drop tube. Problem solved. In over 40 years of reloading a variety of calibers, I had never run into this issue. I was able to seat bullets in cases without powder, perfectly, every time. The runout at the ojive was consistently .003-.004". Once the powder was introduced into the scenario, that's when things changed and my buddy suggested the drop tube. For what it's worth, I ended up with a 12" drop tube.