Agreed, you're probably talking 200+ bucks to rebore and if the present bore is good, there is nothing wrong with .54 caliber and little to be gained from a .58 caliber. Roundballs of .50 caliber have taken deer and elk out to 100 yards with no problem, .54 may be arguably better for elk and moose but the margin is pretty slim. I do shoot roundballs from a .58 Zouave and that is what I carried elk hunting this past season but it didn't help since I never got a shot. I sure did notice the weight of that beast though and next year I intend to carry a .54 weighing not over 7 1/2 pounds.