Personally i have not used a 58, but i have hunted with a few who do. The one guy uses a 62 rifle. All using a patched round ball. I have seen first hand that these larger calibers knock deer flat and with authority.
I have been using a 58 for about 10yearsand like it very well iuse a .577 ball and 18 thousand patch with 90 grains of 2f in the flintlock the cap rifle is a t/c bigboar and roundballs dont shoot that well from it likes heavier conicals cast my own using a lyman mold and 100 grains of 2f
Sure its fun to have a large caliber but the deer I killed with it was not any more dead than the ones killed with my 45,50,or 54.It wasn't knocked off its feet.In fact it went about 50yds after the shot.About the same as my 45's with 50grs of powder hit in the heart.
Get one "just to have" but don't expect it to be a miracle caliber.
My Cabelas 58cal. Carbine converted from percussion to flint is my favorite RB gun. I have another barrel at Bob Hoyt's right now getting reamed from 54cal to 58cal. Also have a Getz 62cal. barrel on a renegade, when using RB's for deer, BIGGER IS ALWAYS BETTER?????
i have hunted with a 62cal trade gun smoothbore and have shot alot of deer with it. it likes the prb and 70 grains of 3f. it shoots through most all deer if shot broadside. the 2 balls i have recovered over the years have traveled half the length of the deer, if shot on an angle.