The main sizes that I cast for are 270, 7mm, 30.06, 303 and 8mm.
Supply shortages in the present reloading market, made me compromise on the gas check sizes. Firstly I size .303 boolits using an 0.316" die and I found that a 32cal (or 8mm) crimped on much firmer than a 30 cal check.
Similarly a 7mm check fits a 270 boolit much firmer when sized to 0.278". Still use 30cal for 30.06 when sizing to 0.310".
270 cast boolit with 7mm check fitted