In keeping with the positive question at the start of this thread, what tools would I take, and have actually taken to Gun shows and the local Cabelas gun room, etc.
An exhaustive list of absolutely everything, probably overkill:
-A very Bright flashlight. (Useful depending on lighting)
-Cleaning rod with patches, like you I have been amazed looking down barrels that were not cleaned since last firing, I doubt it was deliberate to hide something, but is indicative of a failure to care enough. I have experienced this even with some sellers I like and now consider friends.
-Chamber Gauge for whatever gauge you are intending to buy (long term having chamber gauges in at least 12/16/& 20 is very useful)(note some chambers were made so tight they appear short on chamber gauges, but when checked with a Skeets gauge show to be good)
-Bore Gauge to verify bore and degree of choke, and chambers sometimes (again a tool most should have and worth the investment)(without a wall thickness gauge being able to measure bores can help)
-Tape Measure
-Snap caps (though many gun shows put trigger locks or zip ties on the triggers)(if 2in is your focus then cut one down or have one short enough)(used for checking safety, trigger, strikers, and ejectors
-Manson gauge for wall thickness or better an Ultrasonic Wall Thickness Gauge (the Manson gauge is better than nothing and was my go to tool - but a quality Ultrasonic Wall Thickness Gauge provides better data more easily, though at a stiff price)
-Loop of 550 cord for hanging Manson gauge and to hang barrels to ring.
-A postal scale (to weigh overall gun and to weigh the barrels separately)(I weigh all my barrels which from experience does indicate
-Trigger pull gauge (some of us are sensitive to too light or heavy a pull, though I have not used it much if the triggers felt ok, which they normally do)
-A fulcrum or balance to rough check the CoB (I record CoB in relation to the front trigger not the hinge pin)
-A stiff wood dowel or cut off yard stick (to place on rib to aid in measuring cast, drop, etc)
-A reference card for proof marks or shortcut on your phone
-A cloth and oil bottle to wipe down gun when done handling it (can also be used to pour down the rib if the ringing indicated a fault to see if the loose spot can be easily be shown)
-Though I have never brought one a cradle to hold the gun is useful too.
Everything fits in a gym bag.
Most sellers are decent guys, I do not carry the stuff to avoid being taken, but because many sellers are not as educated or equipped and I want to be sure. I also do not go through the trouble of measuring a gun if I am not really interested in buying it. I am always especially concerned about the barrels. It is not for the purpose of pushing down the price, but does disqualify a gun from consideration that was otherwise of interest. I have the kit in my car, but if I do not see the right gun, I do not bother taking it inside.
Over the internet asking questions of sellers has shown me most sellers are not expert, however well intended. Asking minimum wall thickness is most often stupefying. Looking at a gun in person is always better. On several occasions I have been lucky enough to set an appointment to meet a dealer I initially found on the internet at a nearby gun show. I have ended up buying on two of three occasions, though one was not the gun I went to see, but a different one on the same dealers table.
I have found talking through things positively all but one time I have met agreement in checking a gun out. In fact several times sellers have taken notes so they could remember the data. Some sellers are fascinated as they have never seen some of the things I have or measured some of the things I can.
