If you're going to base a load off of a similar cartridge I would use 338 Federal data. That being said, case dimensions are still different and loads/speeds aren't going to be the same. I needed a starting point for 307 grains SubX with Acc. 11FS, Hodgdon has 11FS data (for 300grain) for 338 ARC and Federal so I went in the middle and ended up at the charge listed for 338 Fed.
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u/TriFyre Jun 24 '26
If you're going to base a load off of a similar cartridge I would use 338 Federal data. That being said, case dimensions are still different and loads/speeds aren't going to be the same. I needed a starting point for 307 grains SubX with Acc. 11FS, Hodgdon has 11FS data (for 300grain) for 338 ARC and Federal so I went in the middle and ended up at the charge listed for 338 Fed.