The reason the 175 roundnoses work so well in your 7x57 isn't because they have round noses, but because of the moderate muzzle velocity.
........
Probably the 170's made for the .30-30 would work as well as the 175's from the 7x57 if loaded to similar velocities.
I just put together some practice loads using the old 175 grain Deep Curl bullets at a scorching 2100 fps. I might try them on a pig just to see how expansion is with that bullet at that velocity. My guess is that inside of 100 yards it'll probably do just fine.
