Assume the thing sort of worked when it left the factory - so that includes bore condition, the condition of various parts inside, the bedding, and so on. Some years later, you are trying to evaluate if that thing is still serviceable. If it started as an SKS, is not going to end up today like an H&H or a Rigby. What I found here, is I can not consistently say how well a particular barrel will shoot, based only on what I see in a bore scope - is several here with scratches and gouging on some rifling, etc. that shoot just fine, for my needs. I am not particularly pleased to see pits or sections of rifling that were rusted and now missing - but, typically even those guns will go "bang", and for some people, that is good enough.
I probably do not use it correctly, but the only "real" use that I have for a bore scope here, is when I am cleaning a barrel. I can see what it looks like before I start. Then, I follow the various "cleaner" instructions - then I can re-look into that bore. At that point, I do not care what the sales person said about how good that product is - I can see for myself whether it cleaned out crap or if it did not.
For many rifles, there is a User Manual or there are factory specs that inform an armourer what to inspect - what is still "acceptable" and what should be "junked" - is all about that designer's initial intent for that rifle. You might have a different outlook on what is okay or not - for your "one" rifle - think of an armourer facing several dozen in a pile - all of them need to "work" - acceptably - in a fairly short time - hence the various military armourers tend to have an inspection or gauging sequence that they follow to get the thing into "spec" - to be "good enough for government work" - that might not be adequate enough for your purposes.
Is a mistake I think to read up on various bench-rest and target shooter accomplishments, and then think you will get similar with an inexpensive ex-military gun - is not what they use, and is not what your thing was made for - when it was new. After some use, is not really likely that it got "better" than new.
Is some things besides bore condition that matter, I think - the receiver bedding, the condition of the muzzle's crown, etc. can all influence how well or how poorly the rifle shoots a group. For some people, a "group" is to aim at one thing and take one shot - if target gets hit, then is deemed "good enough". That, typically, is confusing "well-sighted-in", with "precision". A neighbour regales me about how accurate his Ruger 22-250 is - is all based on a single shot that he once took at a coyote on the go in a field - he rolled the thing. From his point of view, that makes that thing a VERY accurate rifle.
