Get a RCBS shell holder #10 (I looked it up to be shure) for .223, with the white plastic piece, and small rod. Been there done that, don't mix shell holders, that goes for dies too. Lee with Lee, RCBS with RCBS... RCBS #3 for .243/30-06 size heads, with the black plastic piece and the large rod.
If you still have problems, take your chamfering tool, the one you use to debur the necks, and give the primer pocket lip about one good turn. If this dosn't solve your problem, the pockets are undersize and will need to be swaged, or reamed.
