The big thoughts:
1. If you are going to load to the same cartridge overall length to feed thru the levergun, the base of the bullet will be set deeper and leave less available powder space and run higher pressures when fired. This is understood from Reloading 101. You could have big problems.
There are idiots all over the internet on websites advocating interchanging data for spitzers in a 30/30 with the flat/roundnose data currently used.
I hope they aren't next to me at the range. You better have a grip on this situation before you follow these "experts" advice.
2. You can interchange the data if the BASE of the bullet is SET to the same depth as a same weight RN/FN bullet, but it will be single shot thru the ejection port ONLY as the overall length won't feed. PERIOD.
3. The round nose bullet will only be about 2 inches lower at 200 yds so what is the need? Round nose are as accurate as spitzers for hunting purposes and generally perform better on medium game.
4. If you have to be asking this question, you better do some more BOOK research on reloading. Bullet seating depth is critical for accuracy as well as safety.