Here is the deal, I have a very nice custom built hawken rifle that was made by a dear friend who has passed away. The rifle has a 54 cal Douglas xx barrel, it is an inch and an eighth across the flats and has a 1 in 48 twist. It is a monster weighing in at 13 plus pounds. because of the 48 twist the optimum charge for this rifle is a mere 70 grains of 2ff. I would like to be able to accurately shoot much heavier loads such as 100 to 120 grains, which I am quite confident the rifle will handle. Therefor I was considering having it re-bored to a 58 cal with a 1 in 66 or 1 in 70 twist. Thought this would even lighten the barrel a bit too. What would be the downsides to doing this and who would you recommend for the job. Also what is a ballpark figure of what something like this would cost? I would appreciate your opinions. Thank You.