This might be more of a rookie mistake, but something to eliminate. When you are seating your bullets, make sure your case doesn't contact the die body. This might happen if the die is screwed too far down into your press. The die will collapse the case a bit and widen it just below the shoulder. The solution of course is to screw the die out a couple turns and screw in the bullet seating screw the same amount.
Edit: I see this was covered in the previous post as well. This can happen with a non-crimping die, too.
Edit: I see this was covered in the previous post as well. This can happen with a non-crimping die, too.
