Even though the 50EX is capable of taking large game at long ranges, just as Blackhawk stated, it is limited by availability of metallic sights. ina modern rifle the 50-110 can easily be loaded to exceed the original Winchester HV data. These loads were quite impressive, even by todays standards. MV was 2200+FPS, at 100yds it was still doin' 1750, and at 200 1350. Downrange trajectory was 1 1/2" at 100, 5 3/4" at 200 and 17 1/4" at 300 yds. Barnes makes 300 and 350 gr .510 bullets for the 50-110.
I would go for a tapered oct. or rd. bbl. of no more than 24". I once owned a lt. wt. '86 50-110 with a 22" nickle steel bbl that got traded for a 45-70 SRC. It was a good swap at the time, and still would be today. The little carbine is in much better condition, despite my having shot it hundreds of times over the past decades.
Whatever you decide, keep us posted on the developements.
With kindest regards,
Mike D.