I have a .50-70 conversion Springfield, and it's a "fun gun" to shoot, although the rather primitive issued sights are better suited to the original muzzleloader barrel. Many of these rifles were used by early buffalo hunters, and recoil is mild. Other than their awkward length, they make great hunting rifles at reasonable distances. Slug the bore, and try to match your cast bullets to its bore size, but black powder loads will "bump up" the diameter slightly. Mine gives me 3-inch groups at 50 yards, but the crude sights are more responsible than anything else. I have a couple of .50-70 Shiloh Sharps rifles, and they shoot 3-inch groups at 100 yards, due to their better sights.
