Your rifle, once you get the right load for the patched roundball figured out, should shoot as good as your cast bullet. While they are not aerodynamic, they are very consistent. And once you learn their flight path the rest is kind of easy.

Now some people will tell you they shoot one inch group with open sights at 100 yards, with a PRB. Good for them. I'd love to spend a day at the range with them, observe them doing it, and learn their secrets to shooting. I can't do it, and I don't claim to do it. If I shoot a 3-5 inch group at 100 yards with a PRB I consider that my average day. Depending in the rifle, sometimes much better. Now twice, I did clover leaf three ball at 100 yards. But for someone that shoots five times a week, every week, that is not an average.

But a PRB is accurate once you find the right powder charge. As for the peep sight. A Williams Peep Sight is a good sight. I have seen them on T/C rifles, but I like the T/C tang peep for the older style Hawkins or Renegades.