Years ago, I was taught to use a "pull tab" from a beer can (Bud) as a quick way to check the gap on my old TR3. The beer tabs used to be 16-17 thou. Those barrels look thinner than a beer tab to me.

Perhaps a previous owner had the barrels backbored or forcing cones lenghtened too far up the barrels? Since the gun was purchased used, there really wouldn't be a way to know withoout measuring the remains of the other barrel and comparing to the proof marks.

Joe