There several iterations of the "improved" 375 H&H, among them the Wby, the Ackley Imp., and the less often mentioned, the 375 Mashburn. I had the latter in a Ruger Tropical for awhile. And there are probably some I don't know of but all give roughly the same increase over the H&H.
In the past I just compared three or four reloading manuals to get a handle on what a top or near-top load for the H&H was (and compared it to the top in this rifle also as I shot it as an H&H for awhile before rechambering) and started there for the Mashburn and worked up a bit. As I recall, i experienced an increase in velocity of 100-175 fps over the old warrior depending on powder and bullet weight. Sorry, I don't have those notes any more so can't be more specific.
Last edited by George_De_Vries_3rd; 01/30/13.
