I have a Ciener .22 conversion kit that I purchased 15 years ago, used it once or twice and put about 300 rounds through it and it has sat in the safe since then. I took it out this weekend but the bolt won't close. That's with an empty mag, loaded mag, no mag, etc. If I take it out of the rifle and manually pull the bolt back and forth, it is very sluggish opening and closing. If I pull it all the way back, it will just sit there sorta stuck. I cleaned it, oiled it up and still the same. I'm thinking maybe the spring? If I remove the spring, it then slides freely back and forth like it is supposed too.  

Any ideas? I thought maybe I would order a replacement set of CMMG springs.

Will it close without the charging handle installed?

thoroughly clean and degunk the channel the spring and oprod ride in, clean and lightly lubricate the spring and oprod. reassemble and test again.

also thoroughly clean the bolt and frame and lightly lubricate where the bolt rides along the frame.

No the issue is the bolt won't close even when it is not in the gun. If I am just holding the conversion kit in my hands and slide the bolt back and forth, it works fine the first few inches and then it gets stuck and won't slide forward. If I remove the spring it slides back and forth no problem.

Yep I have cleaned this thing beyond impeccable. I have oil everywhere. Still no joy. Again if I remove the spring, it will slide back and forth without a problem. If I put the spring back in it stiffens up and feels gritty the further back I push the bolt and it hangs and won't slide forward.

Huh. Sure sounds like the spring has lost its coil set somehow, so that it expands out as it's compressed - grabbing and binding on the inside of the channel. I'd inspect the channel visually if you can, or by feel to see if it's gotten gouged or rough - otherwise a new spring should fix you up.

Yea I played with it this afternoon and ran a Q-Tip up in there and it felt smooth enough. Has to be the spring. I went ahead and ordered the spring kit from Midway. Hopefully that does it. Thanks again for the assist!

The only other thing I can think of is if the guide rod got bent or the backing plate is not square.   If this was only happening in the firearm the bottom of the bolt can hang up on notched hammers.