Loading 45-75. Need some advice

[Joe Amorosi]

I'm light loading 45-75 for an original '76 Winchester. These will be used to test fire the rifle only, not for hunting or target shooting.
The load i have selected is 38gr of IMR3031 behind a 300gr cast bullet but, the load data I have is for a jacketed bullet.

My question is, should I increase or decrease the powder charge for the cast bullet, or just go with the book?

Thanks,
Joe

 

[MTM]

Cast bullets should produce less pressure. That load is quite mild.

 

[Joe Amorosi]

Mild is the point.
Only loading 10 rounds just for function test.
Barrel has been re-lined.
Rifle is a complete rebuild/refinish job from a local gunsmith that needs to test fire before returning to customer.
Looking to get somewhere around 1440 fps