Ok so a lot of people are scoffing at checking out a sks before purchase
I have bought a lot of SKS and have found the criteria for a good shooter...
One that hits under minute of starving german; instead of one that barely shoots minute of fat american.
1) prop the gun on the ground on the butt stock and look down the sites, you will be able to see if the front site is crooked... if its off, find another one, or at leaste select the least crooked one you can. If the front site is off its a ##### to zero... since if its leaning say right; when you go to move the zero lets say two inches down, well you just moved it to the left as well... so you move it to the left and that makes the zero hit low now... see where this is going? you can be at it all damn day getting mad....
2) check the gas tube, when you pop the leaver, it should be tight enough that it doesn't fall out, but loose enough to remove by hand with minimal effort.
If it falls out... its crap, odds are its going to leak and give you a bad string of rounds from inconsistent recoil characteristics.
If its to tight, its going to effect barrel harmonics especialy when its gets warm... this is why a lot of sks groups open up to huge when they get hot.
This isn't fool proof but were talking about an sks, take whatever advantage you can get
3)barrel: try to get a chrome lined one, it will last linger and not rust out if you forget to clean it.... and make sure its not pitted , a good barrel is key to good shooting.
4)Trigger group: make sure it works properly, nothing worse then buying an sks it takes two fingers to pull the trigger, or its so worn out its "like a hair trigger AWESOME!"...only not...
5) general fit and finish.... it should cycle freely, it shouldn't rattle other then that its how much do you care what it looks like....