.225 is a virtual duplicate of the .219 Zipper Improved. I think there was a small difference in shoulder angle and, of course, thicker rim on the .30/30 case from which the .219 descended. SOO... anything said about the .30/30 family and its many descendants applies and the .225 has a bit stronger/stouter brass. (It was to compete with the .22/250, the Swift had been dropped, and work thru bolt actions with the smaller "semi-rim.") The family seemed to thrive on the medium rate powders. 3031 thru 4320, maybe. Ball equivelents. Enough less than Swift to have better barrel life, or so projected. It used to be in the manuals. Mr. Brown, eabco.com, has "house cartridges" on the similar shaped case using the .30/30 rim. 6mm but no .224. luck.