Keep in mind that some of these old rifles have generous bore sizes. I have not slugged the bore of my early 1903 so I do not know where it fall in this regard. It likes the max load from my Hornady book for IMR 4350 - 39.0 grains with the 160 grain round nose. It will deliver near minute of angle accuracy with this load with no pressure issues. If your rifle has a tight bore this might not work.

John