MKane160,

I think the reloader 15 is a bit slow burning. You should get better results from DuPont IMR4064 (very similar to AR2208 made by ADI here in Australia, see http://www.adi-limited.com/handloaders-guide/equivalents.asp ). I got good results from 66 grs of 2208 ignited by a Winchester magnum primer pushing a Hornady 270 gr spite point. This shot just slightly over 1" 3 shot group @ 100 yards. I didn't chronograph it and would be interested in what velocity you get out of it. I think my load was approximating the original British 375 H&H loading, around 2,700 fps. There are some good loads using 4064 at http://www.geocities.com/bw_99835/375Taylor.htm .

How about posting some pics of your rifle.

regards,
Magnum

RL15 is the powder of choice for the 375 H&H but let me suggest you try Varget...almost as good as RL15 and not temp sensitive.