'Brian S' - FWIW: I have no direct experience with this load, but, have long wanted to try .30-30 RN projectiles in a Krag.

I have used 147 grain GI spritzers with decent results. Tricky part is seating bullets out as far as practical (over 3" OAL to have smooth feed and reduce bullet 'jump').

IMHO - You should ignore the bullet cannelure and take advantage of the .30-40 case-neck gripping potential.

My Hornady manual gives the same data for 150 grain Spire, FMJ, and RN bullets.

Per Hornady: Starting .30-40 load for IMR-3031 & 150 grain bullet is 34 grains (2200 fps). 37 grains of IMR-3031 moves about 2500fps. (MAX is 40.1 grains @ 2700 fps).

I see no point in exceeding 37 grains and would probably go with 35-36 grains to start. (IMR-3031 is a nice versatile propellant).