Congrats on your first sks purchase and welcome to the forum here and the world of military surplus guns as you will find out soon there a hoot to shoot!!!!!
Make sure you clean out the gas tube very clean if you shoot it with cosmo still in the gas system it will try to glue the piston to the tube. Its not disaster to repair but when it can be avoided it should be less hassle just to clean it good before shooting it. And take apart the firing pin out of the bolt this is why so many slam fires occur because people will wash it and think it ok because its free but there is a dump truck load of crud still in the firing pin bore that can lock the pin up at anytime and cause slam fires and full auto mode which isn't a good thing to have happen. I like to put the bolt between two pieces of wood with a space between them so that little square of the loc pin can come out when we drive the round pin side out then the firing pin can come out of the bolt. Just wait till you see how much crud is in the bolt. Please do it right and clean it so your safe to use the weapon these guns are getting a bad rap because of their slam firing which is caused by not cleaning it properly.
Now lets get down to business on your Yugo 59/66 now that you have it all cleaned have you deceided what lube your going to use in it? I prefer a moly based anti-seize or you can get by with a quality gun grease too inside the reciever and on the bolt carrier and bolt. I like to put just a little inside the gas tube too this is where the moly excells it can take the heat and keep on lubing/ticking!! I like to put some lude on the inside of the bolt carrier cover too. I like to moly up the trigger group too its the cheapest trigger job you'll ever do. Just lubing it with moly makes a world of difference in the trigger and thats on any gun too.
Enjoy your new FUN gun!!!
BigBill
The moly will reduce all friction, wear and galling the gun will outlast our lifetimes for sure!!!!!!
I'm am still very surprised how well these sks's shoot the reliability and dependablility is unmatched its probably the most bang for our buck we will ever get.
WARNING: After buying one surplus military gun some tend to get a disease after shooting it and realizing how much fun they can be. Then tend to drain bank accounts, spend their paychecks and all their mad money to buy more once they realize how much fun they are. Just beware if it happens feel free to talk to us here for there are many of us here who have this disease too. It just seems to happen with any surplus gun too wether its bolt actions or semi auto's and just the smell of cosmoline can make us go over the edge and hock the farm to buy more just becareful!!!!!!! "kidding" But i'm broke all the time very happy but broke and i thank god the misses handles the money for if she didn't I'd be sleeping in a cardboard box with my surplus guns.