If you're not used to blackpowder, you will be pleasantly surprised. The recoil is much less that anything similar in centerfire. The big, heavy barrel absorbs much of the recoil, and the relatively low projectile speed gives more of a push than a kick. Still, a solidly loaded .58 will jar you a bit. All this assuming that you drive all the balls to about 1,800 fps (656 m/sec) I load 84 gr. FFg in my 50 abd 90 in my .54 and the recoil is not at all unpleasant. It gives a satisfying jolt that I can take all day. The weight of a .570 ball is 280 gr, or 56% more than the 178 gr of a .50 (and 24% more than a 230 gr. .54, which is 27% more than that .50). A .58 kicks about as much as a high-brass 20 gauge shotshell.
A .58 Hawken is a BIG animal gun. Elk and Buffalo. I'd recommend a .54 as a good all around caliber. With a half charge it is good for headshooting small game at close range, too.
What may surprise you at first is the flash. Wear shooting glasses and it won't hurt you. It just takes a little getting used to. :thumbsup: