what i did to fix my sticky bolt issue was first make sure all the cosmoline is out of the rifle, especially in the chamber, which 99% of the time is what causes the sticky bolt. Then go get yourself a 12 gauge brush(correct me if im wrong, im not at home and i don't remember exactly what size shotgun brush i used, will update tonight when i know for sure) which fits perfect in the chamber for cleaning. Put it in a drill and run it in the chamber for like 30 sec to a minute with some cleaning or gun polishing compound. I forget the exact name of it, but i went to a local gun shop and they let me borrow some.
Just don't go crazy with the drill or really fast, just take it nice and slow. After using the brush, get a rag and clean out any compound or whatever you used and try it. If it still sticks, do it alittle more. It only took one time to get my fixed, but every rifle is different depending how much crud is caked in there. That will fix your problem!
Also, i forgot to mention, stay away from brass cased ammo that comes in those packs wrapped with paper and a rope unless it came in a spam can and your the one that opened it. I have found that those cases are usually pretty crappy from sitting so long without any protection with those thin papers wrapped around it. I bought a couple packs of it when i bought my gun and the cases expanded so much everytime, they got stuck or cracked. I switched to a different ammo and worked fine. Try using the brush to polish your chamber first, and stay away from that ammo and you'll be set