Re: Things to look for when buying used?
Its near impossible to determine what condition a barrel is in, other than with a bore scope, and a calibrated eye.
You can stick a bit of cotton into the bore an inch or two and that will help you see whats up in the bore. All you can really see is if its ugly and fouled. Even if it is "fouled", it may not necessarily be a problem.
My Savage is in great running shape, and I could pull it out of the safe right now and it'll shoot...but its "fouled".
Another thing you can do to see if the barrel is SHOT OUT is to stick a correct-caliber bullet into the muzzle. If it damn near goes all the way in, thats a worn out muzzle. This "trick" is really much better done with a muzzle gage, and is really more applicable to war-service rifles that have had the bejeezuz shot out of them.
Otherwise, look the rifle over and see if it was cared for. Wear on moving parts like the bolt isn't a problem, but if its got grit, grime, grease all over the action, someone probably didn't care about it. A good place to look for crapola in the action, is in the bolt-lug recess. It is excessively hard to clean that area well, and it traps all sorts of googe and junk, and is a decent indication of how much field use the rifle has seen. Look for rust too (obviously).
Look at several examples of the same model, if possible. There are often specific ways that specific models will wear. For example, its HARD to tell how much use there is on a Glock. From owning several, and using many, I've learned to look for silver coloration on the slide catch. It takes a good bit of use to start wearing through the black on the catch on a Glock, and it tends to be the first place it shows.
On a Savage 10FP, how much wear there is on the Indian Logo on the bolt is a good indicator. Mine has about 2000 rounds through it, and there is definitely some wear on Sitting Bull, but he's certainly nowhere near "gone".