330 gr 38/55 load

[Scrapiron45]

Just started loading for my Winchester 1885 traditional hunter chambered in 38/55, only mold I have at this time is the Lyman 335gr 378674, a long siloulette bullet. Lyman cast bullet book list 22 gr of imr 4198 as a starting load with cartridge oal of 2.900. To get this round in the rifle I have to seat the bullet deeper to an oal of 2.670. I'm concerned about increased pressures due to the smaller case capacity. Is there a formula to reduce the powder charge relating to diminished case capacity? Or is there some "rule of thumb " to address this issue?
Thanks for any help.

 

[tlf65]

If you are concerned drop your powder charge a couple of tenths and work back up.