The large, 266 grain LEAD ROUND BALL that is fired in that rifle is all that is needed to take either Mule deer or elk. The Maxiball is OVERKILL, which usually means its going to be killing your shoulder and cheek. Unless you practice with these slugs all the time, ( that is expensive), you are going to develope a huge FLINCH with these things. You can't Miss fast enough, or more powerful enough to bring down that game with a second shot. That is why we recommend concentrating on accurate placement of your projectile, rather than increasing the weight of it. Both animals are grass eaters, NOT PREDATORS. Put a LEAD RB into their heat lung area, and they are going down. Spend some time learning to identify, follow, and age tracks before the big hunt. Practice shooting RBs with reduced powder charges at the range, so you get use to the rifle, and its recoil characteristics. Then, before the hunt, go ahead a do some limited practice shooting your hunting load
Your T/C, 32 inch, .58 cal. barrel will burn 103 grains of powder efficiently. A load in the 80=90 grain area is more than enough to kill elk or mule deer within 100 yards, and after that distance, that large ball( or slug) is going to be dropping so much that you would need an electronic range finder to accurately figure out the distance precisely enough to be able to put your projectile on the game.
If you will do some penetration comparision testing with a lead ball vs. a maxiball, and compare both of them to any modern " elk " rifle y9ou might have, I think you will find that the RB is more than enough. Based on tests I have done with other calibers, I would expect your .58 RB to go through 8-one inch pine boards, spaced an inch apart, or through about 16 inches of flesh and bone, the same as a 180 grain Jacketed Round Nose .30-06 bullet will do. I don't think anyone will argue that that .30-06 load won't kill all the mule deer and elk you can find! And it puts a much smaller hole in the animal than your .58 will do.
Remember there are 437.5 grains to the ounce, and that 266 grain RB weighs about 5/8 of an ounce. Its HUGE, and once it gets going, it keeps going until it hits something solid. Flesh is not a solid. That heavy RB will also crush living bone quite well, and pass through shots on elk with that caliber of RB are rather common. The same can be said for the slightly smaller, .54 RB. And, Lead RBs do mushroom well in flesh, leaving a half dollar sized hole through the vital organs. Death is caused by hemorrhaging, and the sudden drop in Blood Pressure, depriving vital organs and the brain of needed oxygen.
If you insist on using the Maxi-balls, please go to the Member Resources section here, scroll down to " articles ", and read my article on controlling heavy recoil. It will help you be able to place some of the bullets some of the time, at the POA. I can't overcome the flinch you are likely to develop, but you might still put one of those slugs where it will bring down the game quickly.