RCBS AR sizing die issue

[parkerg31]

I recently got into 300 HAMR for hog hunting, and am using the RCBS AR two piece die set that Wilson Combat sells to reload it. I am having issues with my seating die now that I am trying to resize my fired brass. The dies are creating a taper on the case neck almost like a early bottleneck. I resized my new brass before loading the first go round and did not have this issue. The neck OD increases from .325" to .334" prior to the shoulder, where on factory new brass it maintains .325". It does pass the cartridge guage.

Any help would be appreciated. Yes, the dies are set up correctly and I have 15 other calibers that I load without issue.

 

[tomme boy]

your full length die is screwed in till it touches the shell holder with the ram all the way extended right? run a piece of brass up into the die but do not lower it. look under the die between the die and the shell holder. Is there any gap between the two? If there is then screw the die in more till the gap disappears. Or the case is fully sized. This is where everyone screws up setting their dies. Especially when you are converting brass into a different cartridge by the looks of your brass. Are you using 223 brass?