I've just read an article by Mike V. in Handloader or Rifle stating the Shilo is now rifling at 22" twist in the .50's. If this is correct and I see no reason to disbelieve Mike, it's GREAT news. Any bullet ot 600 or 700gr. will shoot, as will the 450gr. Lyman or RCBS Fn bullet.
: RCBS 550gr. FN and Lyman 520gr. are also a good, accurate grease groove bullets.
: A PaperPatched bullet would be fine, but for repeat shooting, needs special wads a sin a wax or wax paper disk between the BP lube ball and black powder, then card wad, then bullet. This takes up a lot of powder space in the caae, but he bullet need only be in the case about 3/16" as the rest wil slide up nto the rifling. The Patched bullet should be bore size to .001 over bore size for BP loads. Cast in pure lead, they'll slug up and shoot exceptionally well, for strings of 10 if you want.
: With smokeless loads and paper patched bullets, the lube ball is not needed, but there must be lube on the paper itself and the bullet will need to be patched to.001" or so over groove diameter. They should shoot very cleanly, giving exceptional expansion on game to whatever range you can shoot accurately.