Below is an excerpt from a long ago post by Marshall on this very subject. Hope it is useful to you.
For the .444 and a light load:
15.0g Unique/Any Lg Rifle Primer/240g WFNPB or 250g LFNGC sized to .432" This load is very pleasant to shoot, and generates about 1300 fps. Also very accurate, except the PB bullets don't perform well in Ported Barrels, the GC bullets do great!
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