Hey, I've got one of them. The one on the far left the stick figure is looking down the bore of. Mine's bored golf ball. Be aware all golf balls aren't the same diameter. Mine is Titleist. Ammo is where you find it.
The load the guy gave us was 2 or 3 caps of black powder. The seller said that load will send the golf ball through a car door. But then he suggested we not stand directly behind it. If it doesn't penetrate, you don't want to be where it comes back at you!
First day we had it over at the gravel pit. We went up on a hill top (big pile of gravel) and fired it a few times, at the elevation the carriage gave. A lot of smoke, no one saw the ball go. Even standing off to one side. Finally one of the guys (he was less inebriated) suggested we use one of the colored golf balls, only use one capfull of black powder, and then kick some pea gravel under the carriage so it would shoot level. We had plenty of fuse, powder and golf balls. Nothing to lose so we did.
Our expectation was for it to barely come out, then bunce a few times as it went for the Great Miami River. We heard the blast, and for once saw the ball going out. Great line drive, maybe 500 yards straight out. Went into the trees by the river and probably into the play ground on the other side. Whoops. Then we stopped, figuring the first few shots hit the rich subdivision up on top of the next hill.
And I've got another built out in Phoenix. Its got a 1" bore, and even came with a bullet mold, 1" round ball. That's 4 ounces, or a quarter pounder, just like McDonalds. Haven't fired it but I've owned it for probably 15 or so years.