Of all the "off the shelf" guns available today, I like the Lyman GPR. I also like it in .54 with the slow twist. Quite simply, it puts metal on target. They shoot good right out of the box, no muss no fuss. The sights are quite workable as is. Cap or Flint, your choice. The GPR is an excellent representation of an American Plains Rifle, a composite if you will, of many guns made at the end of the muzzle loading era.
I make the above comments with a battery of high end custom guns at my disposal. The GPR is more than competitive against the expensive guns.
The patched round ball remains popular for a reason, it is both accurate and effective against game.
One shot, one kill.