If you want to be in the old double game, either buy the proper tools and become proficient in using them, or find someone who is. Do not assume, or take the sellers word for anything. What is a few hundred dollar one time investment, when you are talking about buying guns which cost much greater than that? The guns on my gun room wall racks may only cost $500 to $15,000 but when you multiply them out for the grand total it becomes a lot of money. Bad barrels can drop a gun value by 90% or even make it worthless in many cases. The tools used to verify their conditions and safety will last decades so when you think about them they have measured more than a few hundred guns already. My cost per gun is very little for the tools I have bought. My barrel wall thickness and bore measuring tools cost me about $600.00, maybe nearer to a $1,000.00 when I think about duplicates and upgrades, so I understand not everyone needs to invest that much money, but you do need to find a gunsmith who has them and will carefully measure your guns and inform you if there is anything you need to be aware of or to fix before safely shooting your guns.
My guns are all shot, by me or my sons and friends and no gun gets used until I know as much about the safety to use it as I can learn. Chamber length, bore diameter, barrel wall thickness are all measured and verified before I ever drop a shell into any gun I own. Do not care if it is five year old, or 200 years old, they all get checked out just like they all get a proper cleaning when they come in the door. Anything that needs fixing gets fixed. My oldest muzzle loader is almost exactly 200 years old and it took three wood ducks two years ago. My 42's get regular use on dove and sporting clays. If I own it, it will be shot. Guns were made to be shot and enjoyed, not to be a status symbol or an investment. Mine might not get shot often because the field is crowded, but they all deserve their day in the sun.
