Hi Dave, Mike pointed out the issue for different barrels. All modern Pietta barrels and frames will exchange fit perfectly. However, this early Navy Arms (Pietta) has a barrel arbor hole much like the Uberti's, a taper at the hole bottom. I'm going to try to drill through the end of the barrel arbor hole and tap for a 10-32 set screw. I hope the angled metal at the area of the loading lever doesn't blow the drill hole elliptical. Even if that does happen, the hole will provide expansion area for JB Weld to set the correct gap. Clean the barrel arbor hole with acetone and put grease on the end of the arbor. Assemble the gun with a desired gap letting the JB Weld cure. Then pull the barrel off the arbor.
Regards,
Richard