Here's my Bro's Shiloh, in .50/90. His accuracy load is 600gr. SP BuffaloArms mould powered by 91gr. Swiss 1 1/2F. This rifle and load placed 1st and 2nd (I used it too) in the Quigly match at Rendezvous BC 2015, last year.
This rifle started life for him, as a barreled action in about 1980 or 81- stocked by him in Claro Walnut - with a Niedner butt plate - and .45 3 1/4". Took us 8 years to find a cast bullet load it would shoot with BP in it's 1 1/2" deep rifling. He shot numerous 1" to 1 1/2" groups at 100 meters with smokeless and jacketed as well as black powder and 500gr. Hornady Jacketed bullets. It was not until we tired bore sized paper patched pure lead 400gr. bullets and black powder that it shot well with cast bullets.
The rust blued barrel on it now, as shown in the picture, is a McGowen 24" twist, #3 heavy taper x 28" bl. Last summer, I watched Taylor shoot a 2", 5-shot group at 200 meters with this rifle off the simple 'chunk' rest he is using in the picture - with no rear bag. That Harry McGowen, St. Anne. Illinois barrel shoots. Rifle weight - 11 1/2 pounds.