But, I wouldn't be afraid to use them.
FWIW, I do most all my hunting/shooting with cast bullets. My favorite is the RCBS 150gr flat nose. These bullets won't mushroom, per se, but they do "rivet" to a given extent.
I don't see why you would have any trouble getting 2100 fps+ from your 16 1/4" barrel. That should give you plenty of downrange velocity, to initiate expansion, given my admittedly limited experiences with the SSTs in rifles, at least as far as I would attempt to take game with the .30-30. Just be sure and place it right, which is MOST of the shot, anyway. JMHO..........Bug.