OK, so what we need to decide is what type of round ball shooting are you interested in?
Primitive would be no adjustable sights, cannot think of any other rules that would limit you. Some totally PC guys might not be excited about seeing a factory gun.
If you are in a trade gun match, obviously you could not have rifling and most exclude rear sights as well.
Most club matches might allow the fiber optic front sight, some would not.
Offhand matches usually have a weight limit of 12 or 14 pounds to the rifle.
Typically, black powder or synthetic can be used, but some clubs might not allow Pyrodex.
Just taking random thoughts as they rattle around the brain pan (it's a lonely place in there.)
Best bet is if you have questions, try to get in touch with someone that is familiar with the range and their rules. It's easier to find out before hand than after the fact. I was shooting a silhouette match at Friendship one time and stupidly used a rifle with a peep sight. Much to my chagrin, I found out my very proud score would not be allowed. Oh well, shame on me for not knowing what I was doing when I got there.
John