Are your FL dies adjusted right? It almost sounds like you are squishing the case down too much. Check the case length. If it is correct, check case length on a fired cartridge and compare the two.
Another thought: is the chamber too long causing case stretch? In that case you would want to neck size only, then trim the case to length before priming, charging and seating the bullet. If you full length resize evry time, the case life will be severely shortened. Most of my reloading is with a Lyman 310 tool which neck sizes only. I don't FL resize until the cases will no longer feed into the chamber (I check this after sizing, before I go on to the priming and subsequent steps).
Let us know how you make out!
-WH-