“Case capacity differences between .303 and .30-30 is negligible. In fact, my standard hunting load with 190's in both of them uses the same weight of powder, 28gr. 3031, and the difference in velocity with equal length barrels isn't worth telling your bartender about.”
I think it’s fine to use 30-30 data for 303 Sav with 3031 and some other powders with 150, 170 and even 180 grain bullets.
If you are interested in loading the 190 Barnes for 30-30 I would not rely on 303 Sav data entirely. I don’t know if Barnes publishes 30-30 data for their bullet but if you go to 303 Sav data as a guideline, start at least 3 grains under and I’d be very cautious about trying to get within 1 grain of the 303 data, particularly in an 1894 or 336. Max grains for W760 is 36.7 and LVR is 38 and these would be compressed loads.
