A pound-cast of your chamber and throat will tell you what you need for both brass length and bullet diameter.

A marked cleaning rod and a tight patch will tell you your rate of twist and what bullet weight you can get away with.

It's a great round that gives more mass than a .30-30 and more (or equivalent) sectional density than the lighter .458's and is pleasant in the recoil department. Guys use the faster twist models with heavier spitzers for competition at distance, but that's a matter of being on a known-distance range. For hunting, I'd regard it as the rainbow trajectory round of the 1800's that it is and treat it as a 150-200 yard timber gun.

It should do the job on elk, but I've come to the conclusion that if the hunt is going to be distant, expensive and/or difficult, the gun will be stainless, synthetic, and with an effective point-blank trajectory of about 300 yards. If I'm shooting them out of my backyard petunia patch with a resident tag, that's another matter.