Buying a Preowned Rifle

This is mostly intended for folks not on the ML Forum.
I doubt many riflemen would happily sell a deadly accurate rifle.
Reasons for selling a rifle:
Have a more accurate rifle
Cannot get accuracy out of this rifle
Reasons for no Accuracy:
Ignorance of any idea what is required to produce any good performance
Barrel ruined because of ignorance
Barrel ruined by carelessness
Bulged barrel caused by not seating a patched ball before firing

Fastest way to ruin a barrel?
See line above.
What is a slower way to ruin a barrel?
Not cleaning at the end of any firing and letting corrosion prosper.
What is the usual reason for selling a rifle?
Can’t get any accuracy for the above variety of reasons. And there you are.

“Boy, I have gotten a great deal on a Whizzer Bang Bang .50 Super Deer Killer hunting rifle” made by an unknown gunsmith.

HOW TO PREVENT JOINING THE PARADE OF FOLKS TRYING TO ACHIEVE ACCURACY OUT OF THIS GREAT DEAL.
All a rifle is is the barrel. Nothing more. Nothing less.
All the rest is just an apparatus to make it fire and to hold it steady while aiming.
Pretty appearance is nice and frequently inspiring but is most appreciated about wall hangers.
A good unbelted barrel is about all you need. It can handle a surprising amount of pitting from old uncorrected corrosion created by the prior owner. It CANNOT handle a bulged barrel. There is seldom any sign of the bulge on the outside of the barrel so how do we check the inside of the barrel?
Place a couple of patches on the jag end of the ramrod thick enough to keep the patched ramrod sliding effortlessly down the length of the barrel. Preferably it will slowly slide down the length of the bore with just the weight of your arm.
Observe closely. Does it slide down at the same even speed the entire length OR at one point speed up for two or more inches and then slow down again? No speedup, you might very well have a good barrel. If it does speed up, you may have the greater part of a crowbar. It will never shoot accurately. Don’t buy that rifle. If the person selling won’t allow this test just walk away. He knows what’s wrong and doesn’t want the buyer to find out. He is a thief. Never buy anything from him.
I have had too many people come to me with a “great deals” that turn very sour when the hidden bulge is discovered. Wonderful as you are, you can’t work around this. If you can, please let me know how you did it.