The military specification for the original M-2 Ball ammo was quite simple:
IMR-4895 powder
48 to 50 grains depending on batch
150 to 152-grain slug.
I load mine with that Hornady 150 Spire Point..... which is not quite the correct shape, but that deep cannelure makes finding the seating depth very easy for older eyes.
Works fine: SA 4337999 groups well under an inch at 100, off the bags.