Back your crimp off .
What is happening, it doesn't matter to jackets, is that the crimp is getting applied before the bullet is seating to depth .
You're probably also under sizing the bullet with the crimp and setting it up for leading. The lead bullet should be about .4015-.4025 vs the jacket being .400 also . Back the die body out about a 1/3-1/2 of a turn then reset your length and se if that helps .

With cast bullets you really only want to just remove the flare and have enough to avoid hang ups and failure to battery . There are exceptions like tubular magazines and powders like H110 where the crimp keeps the bullet from getting pushed into the case and is used to build start pressure. Neither should be involved in a 40 .