When I’m cleaning a shotgun barrel, there is usually a can of WD-40 on my bench. Right next to that is a proper bore solvent, Outers and Remington brands are there today. I toot some compressed air down the bore, which, removes some of the dry crud. Then, mostly because it has a tube to direct the spray, I hit the bore with WD-40, and run a patch or three down the bore. I spray the bore cleaner (both come in pump plastic bottles) down the barrel, brush with a bronze brush, and finish when the patches come clean. I never oil a bore. The guy who ran the French proof house in St. Etienne explained why I should never do that, and, I don’t.
Nobody ever told me to use WD-40 to initiate bore cleaning. I think I just started doing it because it was handy, moved the heavy crud, and allowed me to see the bore in a bit cleaner fashion when I got busy with actual bore solvent, and a bronze brush.
I will use a bit of WD-40 on a clean cloth to wipe fingerprints off of blued metal. It actually gets used for very little in my world, and a can runs most of a decade if the pressure doesn’t seep out of it over time. A few have done that to me.
If you are taking a stock off a double, hosing it with WD-40, and calling it cleaned and lubed, you need to up your game. It isn’t clean, or, lubed.
Best,
Ted