Maybe not the normal sticky bolt.
I have a bubba'd ex sniper I am turning into a 20 scout rifle.
This is the only one of my collection to have a sticky bolt issue.
Bolt operates smooth with it cocked, very hard to open after pulling trigger (regardless of having live round or dry fire)
I polished up the contact cocking surfaces on the back of the bolt with no improvement.
I swapped in the bolt from my baby's ass smooth Tula and get the same issue with it in my ex sniper.

Not sure where to go from here to smooth it out.
Ideas?
Attached File

Get all the dried cosmo out of the chamber, inner receiver bolt area and throat. I have used a wire brush on a cordless drill with good results...try the chemical of your choice...sometimes heat is your friend...If it's clean and still sticks use a competent gunsmith.

This is with no round in the rifle, so it is not Cosmo in the chamber, ECT.
I'm not taking a $70 rifle to a gunsmith.
Has to be something on the rifle end of it since swapping the bolt had no effect.
Although I'm not sure what it could be.
Bolt is Smith when cocked, hard to open when in fired position.
So what is different in the contact surface on the rifle between cocked and not?

the buildup of hard caked cosmo between the bolt face and barrel and the bolt lugs. If you are willing to shoot a 70 dollar rifle without having it checked when there is a problem I guess I won't say another word.

Indeed.

Take the action out of the stock and warm it up to melt out any remaining cosmoline in the receiver's bolt locking lug recesses.

Try swapping out trigger and seat with another mosin and see if it is trigger and seat parts.

Seat=sear. Fucking auto correct.

That poor gun.... You realize those are 200-300 dollar guns now?
First of all this is not sticky bolt, if it don't occur after you have been shooting for a bit and feels like there are rubber bands holding you bolt shut it is not sticky bolt.
As for the difference, they are contacting. The rifle is full cock on open, so the only time the cam surfaces contact is when your cocking a de-cocked bolt. Not knowing that dose fair well as to your ability to find the issue with that gun. On the bright side you pretty well ruled the bolt out, you can always test the bolt in the other rifle just to fully rule it out completely. So it is time for you to look at the rifle it self, Ejector/interrupter, seer/trigger, magazine/follower, head space, locking lugs you know pretty much everything that contacts the bolt.  Seeing as there is enough issues possible in that area you could write a decent sized book on it, I suggest you take it to some one that at least knows some mosin fundamentals.

RIF.
I know it's not regular sticky bolt, I said so in the op.
I also know that the camping surface are only in contact when the bolt is in the fired position, and said as much.
You should probably refrain from offering advice on the internet if you cant be bothered to read what you are responding to.
So you can take your high and mighty condescending attitude somewhere else.

Well someone got salty quickly.

If your not going to try troubleshooting your rifle and just magically assume the internet will know the answer to your rifles issue then yes I am going to talk to you condescendingly. You don't give barely any helpful information to troubleshoot your rifle. Also your not fully reading the replies, people are giving your very valid suggestions that your ignoring.

Lets see, what do we know.

Good, you took the bolt mostly out of the equation. That also means all your information about what you did to the bolt is pretty much irreverent because you ruled out the bolt, so no need to keep restating it.

Well this is pretty normal, assuming that is suppose to be smooth not smith, it is after all a cock on open. So lets just assume it just cocks a bit harder then it should. This tells us it is likely not interference from the interrupter/ejector as these mostly interact with the bolt the same regardless of if it is cocked.

Ok, so we know it dose it with or with out a cartridge chambered. So you ruled out the chamber defect and head space.
But your only partially right on the Cosmoline. You are forgetting about the locking lugs, which is what dIIshoots, and lew were getting at.
Clean the lug groves, this is a pretty common problem area for mosins.

bradleyswine has a good point, it might be a collision on the seer, but rather then swapping it I would first try to action it with the trigger depressed. Unloaded of course.
If those don't help it is time to start pulling parts. Remove the mag well, try it. Remove the stock, try it. Remove the trigger/seer, try it. Remove the interrupter/ejector assembly, try it. If it still has issues at that point your in trouble. At that point your down to just the barrel, receiver and bolt, and you ruled one of those out. So go, troubleshoot, locate the problem part/s then comeback and maybe then the internet can actually help you fix it.

Better yet is to take it to someone with mosin knowledge. They could check a lot more in just a few minutes just by physically handling the rifle.