Howdy
Yes, this is fairly common. I had the problem with a used Uberti Cattleman that I bought a bunch of years ago. The burr was so bad the gun was completely bound up with live ammunition in it. I had a great deal of trouble removing the cylinder so that I could empty the gun.
The firing pin on a Colt style Single Action revolver is designed to 'find its way' through the hole in the frame. That is why the pin is free to rotate up and down slightly in the hammer. As the hammer falls, the firing pin rubs against the sides of the hole in the frame. As the frame material is rubbed over and over this way, it can raise a burr on the face of the frame exactly as you have experienced. Real Colts have a hardened steel insert pressed into the frame to prevent this from happening. The imports do not have this pressed in insert because it adds to the expense of making the gun.
I have heard it said that excessive dry firing can cause the burr, although frankly I don't see why dry firing would be any different than live fire, unless the gun is dry fired a whole lot.
There are a couple of solutions to this problem. The first, and easiest thing to do is to file down the burr. Take a fine cut flat file and lay it flat on the recoil shield where the firing pin hole is. Pressing down on the body of the file to keep it flat on the recoil shield, take a few light strokes to remove the burr.
Unfortunately, the burr will probably return because the firing pin will continue moving material around. What I did was to take a very long drill, that would reach all the way through the barrel to the recoil shield. I wrapped the sides of the drill with tape so it would not scratch the bore. Placing the tip of the drill in the hole I very carefully and very gently chamfered the hole. This way, any new burr material that showed up would fill up the chamfer and not rise up to cause problems. I caution you to be very careful if you try this approach. Just remove a teeny, tiny bit of metal. Remove too much and you will enlarge the hole too much, allowing primers to flow back into the hole, binding up the gun. Just remove a teeny amount of metal, turning the drill gently by hand with your fingers. One revolution of the drill is probably all you need.
By the way, Pietta does not make a SAA, nor does Uberti. What they make are replicas of the Single Action Army. Single Action Army and SAA are registered trademarks that belong to Colt. No other manufacturer uses the words Single Action Army or SAA because they know Colt will sue the pants off of them if they do.