I ordered a 454-260 Gas Check along with some gas checks for my 45 Colt chambered rifles and revolvers. I plan to size these through a lyman 450 lube sizer. I slugged all my barrels and they all measure at exactly .442 and .450 for the bore and grooves.

The question is, what would be the best size die to use for these? .452? .454?, .453? , .451???