1885 High Wall or 1874 Sharps?

[Don McDowell]

The biggest problem you'll run into with the Uberti Hiwalls is their barrels aren't necessarily match quality. I do know of several of those that have been rebarreled with good barrels and make fine competition guns.
Beside the Winchester/Browning hiwalls, don't over look C Sharps.
Sharps rifles I believe are best left to either Shiloh or C Sharps, as the price difference between those and the better quality Pedersoli's is non existant.
Keep an eye out on the For Sale section here, there have been a number of rifles come and gone. Gun Broker has a goodly number of listings at the moment as well.
You'll find a world of difference between your highpower and the bpcr shooting. Stuff that won't even make a SMK flinch at 200 yds will make a bpcr bullet puke it's guts out. It's not uncommon for High Master highpower shooters to spend a few years in the Marksmen/Sharpshooter class when moving over bpcr.
Good luck with your purchase, and welcome to the sickness.