I also have an old box of 50 Buffalo Bullet Company MAXI BALL-ET's 270 Grain lubed with what looks like bore butter (like my pillow ticking patches).Isthis a good bullet to use for Whitetail with my T/C Firestorm with 1/48" twist and BP?
Absolutely.
I'd start off around 90 or maybe 100grains and work up a hunting load from there.