Fitting Gas Check - what size?

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

https://i.imgur.com/CtMbKoRm.jpg

My question would be the end results. Are your GC bases completely flat and perpendicular? If so, you are good to go, but if not?

You might want to check around.
Somebody up & down here makes & sells the tool to make your own.