I have a CVA .50 Frontier rifle that's a smoothbore rifle.
It's an older, less common model that came in a black & white box.
Maybe that's what you have but in .54?
It does look like a Hawken with its 1/2 stock & double triggers.
I happily bought it from someone who didn't realize that it was smoothie when he bought it online, so he quickly resold it.
Smoothies are usually easier to load with balls that are undersized by .020 instead of .010 because the barrel doesn't have any rifling grooves to hold the powder fouling and any extra patch material that covers the loaded ball.
It should be capable of shooting a rifle like group out to 50 yards at least.
But tighter patched balls are generally more accurate.
And .520 balls are not as easy to find anymore since Hornady discontinued making them.
However Track of the Wolf sells hand cast balls in .520 & .526.
http://www.trackofthewolf.com/(S(l4...atId=2&subId=25&styleId=58&PageSize=25&Page=2