They make really high quality barrels. However, if you want an actual rifled piece you must also purchase a carriage from Paulson Brothers Ordnance, they will not sell you a rifled barrel without it (PBO makes/provides the liner). You can purchase a smooth bore barrel from them w/o a carriage...
I went with Steen Cannons for my two rifled Parrotts a few years ago as I already had the carriages. Steen also makes very high quality barrels. In fact, we won the Bacon Creek Match at Camp Grayling Michigan this year with one of our Steen barrels, a 1,000 yard match shooting into a single sheet of newspaper (recreation of an actual historic event). After one sighter shot we placed the next 7 out of 9 rounds into the 4'X6' wood backer, 3 of which were in the newspaper (a 4th missed by an inch). We were VERY pleased, especially considering we had never shot beyond 600 yards before, and no other unit hit the paper even once! It was a bit warm making sighting difficult (heat waves) and windy. We had to point our piece just left of the target to get it to come back on target with the wind! BTW, these were 3" diameter 10 lb. bolts with a full service load of 1 lb and they still drifted approximately 3', and the front sight looked bigger than the target at that range...
At home we can shoot bulls eyes every time at 600 yards pointing dead on. Down side is if you do not make your own ammo it costs approximately $75 per shot with bolt, powder & primer, and the average shoot takes 15 rounds.
Anthony