Three ways to fix it, AR. Way #1 is send it to the Goon. A decision you wouldn't regret by any means...
Second two ways involve your confidence in your own work, and competence of same.
Way #2 involves fabricating a thin SS shim, preferably out of shim stock probably .010 to ride between the cylinder and recoil shield. You could "most likely" secure it to the present recoil shield wear ring via JB Weld or similar structural adhesive. I say "most likely" because I have never actually tried it...only cogitated on it. Bt it should work in theory. I believe the original Manhattan brass Colt clones used something of this nature...how you worked it out and how well it worked would be in your hands...
Way #3 involves removing the barrel and cylinder, then taking a pair of needle nosed vise grips and removing the alignment pins in the frame. A little judicious heat on the grip frame (hair dryer, heat gun, etc) and the pins should walk right out (they are press fit). Slip the barrel back on the arbor, apply valve grinding compound to the two mating surfaces, then work them back and forth. The two surfaces will lap each other parallel and square, and the soft brass will be the sacrificial part to wear, allowing the forcing cone to move closer to the cylinder. All you need to lap is again around .010. You can check your work every couple of minutes. Just don't get any lapping compound in the innards of the gun!
After you get the gap where you want it, clean out the pin holes on both frame and barrel, tap the pins back in, and reassemble. You should be good to go.
Whichever method you choose, good luck! And it would be great if you could snap some pix if using method #2 or#3 and share in the "Gunsmithing" section. You're not the first to need this done and certainly won't be the last!
