I have been pondering the causes of inconsistency and I can see where an anvil made to conform to the ogive would yield consistent results as long as the ogives are consistent. As painter said, if the ogive varies it seems to me that it could affect the OAL because the contact points will vary. What do you think about cutting one designed to only contact the meplat?
I make new anvils for the Dillon dies all the time. Dillon really doesn't have a good answer for conicals such as the Hornady XTP and TAP, and the Precision Delta JHP. In those I push on the ogive and not the meplat. This because 1) there really isn't enough physical support to push straight-on. Yes, you'd get really good OAL reading and low variations, but the nose of the bullet would simply collapse to different degrees depending upon how fast I swung the op lever.
2) Besides simply pushing on the bullet, one of the other jobs of the seating anvil is to Center the bullet in the case. The bullet can't fly straight if the axis of the bullet is not loaded onto the axis of the cartridge. That point is a LOT more important than OAL.
So a correct fitting anvil is doing 2 important jobs.
Junior Partner here: I can't reply to your message or post a personal message to you, nor even email the administrators to ask for help. I keep getting error message which perhaps is a polite way of telling me I am drooling while awake. So I'll do it the hard way. I am asking you about used Dillon equipment and about the anvils for seating fp and swc bullets. You're welcome to reply privately. 
You need to have 25 posts to be able to send a pm. Keep on posting worthwhile replies and posts and you’ll get to 25 in no time.
Or you can go the easy route by posting replies such as “welcome” “me too” etc 😆
Thank for that! Grendel also sent me a link to the appropriate rule. I'll keep reading and when I have something to ask, or hopefully add, I'll post more often.
