Originally Posted by Burien
I have not seen the REX Magnum powder around, I have used REX II for a few years now and use it for most all my calibers, I have not used it with 10mm yet, I'm thinking 5.5 grains to start out with for 180 gn plated bullet. REX II has usually followed load data of Titegroup by grains, but titegroup is much smaller when you look at the volume it takes up in the case. I'll post my findings some time soon.
IMO Rex II is way too fast for heavy 10mm bullets. Maybe only for 135gr but got to be very careful, I can't give you any starting data for Rex II & 10mm. Well, I've been experimenting a year ago with Rex III but you can't get out some hot loads with it...maybe weak plinking loads only.
I can recommend only Rex Magnum. I can't see any reason for Rex M. not to be available in USA because Rex II and Rex III can already be bought there.
For mild plinking/target loads I use 10gr Rex Magnum and 180gr copper plated bullets (1200 fps)
I will try to find my data for Rex III. Anyway, Rex powders are very interesting because of their low price, clean burning and availability for making compressed loads like mine 12gr/180gr and 13gr/165gr are.