I just picked up a 45 caliber Gonic rifle, and am starting to mess with it. Funny they call it a .458", since usually muzzleloading rifles are measured according to bore size. I was lead to believe that was the bore size, but it is not. It's a normal .450X.458 barrel. No sweat, I have .449" sizers to make bullets. Now I see why folks complain about not being able to find bullets to shoot in these rifles. I shot it some this last weekend and wasn't too impressed, then yesterday I checked out the scope and found it didn't work, so those results don't count. I fitted it with a set of iron sights, the rear from a 1901 Krag rifle so I have lots of adjustment. Also fitted an old 4X Leupold to it, that I know works properly. Now to give it another try next weekend...
I'd love to hear from others who have these rifles and what you think of them. I really like the design and it looks like it's going to be a good one once I get it sorted out.