I have been working with a Remington 40X in 308 Winchester and up till now I have only made a expander and used some JB Weld for a custom fit of the bullet seater die and my record five shot group at 100 yards is .305". Well I put some thought into getting the rifle to shoot even better and with fewer flyer's so I am going to show some pictures of the dies that I am using and the modifications that I made to them. Before I was using a LEE collet neck die with Federal cases that have .0015"+ neck run out and when Lapua came out with the new 308 Win Palma cases with the small primer pocket and flash hole I purchased 300 of them. I am now going to use a Redding Competition bushing neck sizing die that has a sliding chamber to hold the case during neck sizing. Well this got me to thinking why not have a expander die with a sliding chamber to hold the case with a carbide expander to get the best concentricity to eliminate bullet run out. I purchased a Forster Bench Rest Seater die with the sliding chamber to modify. The first thing I did was to set it up in my lathe and ream the hole that was made for seating a .308" diameter jacketed bullet to .312" and then designed a floating carbide expander with a .309" diameter section for the bullet with a .3119" diameter to bell the case mouth and align the expander in the sliding chamber. I also bore a groove for a rubber O-Ring in the lock ring.