In the Double Gun Journal an issure or three back, a guy wrote about how he tightened up a Nitro Special with sheet brass, doing the "repair" in the early 1960s, using (abusing, actually) the gun as his duck gun, with serious duck loads, for like, two decades, and selling it off to a guy who did more of the same. I had Mike repair a worn gun (a Tobin 12, not worth a big dollar fix) with a soldered shim, it works quite well.
I think I'd measure how much of a shim it needs, and use oiled paper for a while, to get a feel for how much you want to spend. Typical typing paper runs about .004, and lasts so long you might never do a "good" repair.
Best,
Ted
