I'm not sure if they have barrels, but you might check with October Country Muzzleloading in Hayden Idaho. As others have said, you probably will need to look for a tapered barrel if you want to go to a .62 caliber. Rice would be a good choice. Years ago, Green mountain made a 1" straight rectangular barrel in .62 caliber, but they were smoothbore. They also made 32 inch drop-in barrels for T/C Hawken and Renegades. Quite a few of us on the forum at that time bought the .62 drop-ins and sent them to Ed Rayl to rifle for us. He felt there was enough clearance at the screws to allow it and they seemed to work well then and mine still does. It is rifled 1:72 and I shoot a .595 ball with 0.15 patch in front of 90 grains of 2f Goex....and yes, I still hunt with it. Nothing this year, but this was a mulie buck I took with it last year along the Snake River. If I remember right, this gun weighs right at 9# with the sling. Do you need a .62 caliber for deer, elk, or even moose....no, but it's just different and neat! (I do like my ramrod a bit longer than the barrel, but I think it was pulled out a bit further in the picture)
View attachment 185188