Took apart an ASR, cleaned everything and replaced the o-ring, lubed everything with silicone oil, and reassembled, only to find that the bolt will not close properly. Previously it had closed nice and smooth. All I replaced was the o-ring on the piston, and the piston slides freely in the cylinder with the new o-ring sealing correctly. When the bolt is inserted into the receiver it slides smoothly, and when the gun is assembled and the bolt is pulled back it slides smoothly, but upon cocking the gun, the bolt becomes very tightly bound, and is very difficult to push forward. It almost seems as though the spring guide is tilting and binding against the cylinder, but I can't see how it would do this with such binding force, like the spring guide is digging into the cylinder. Any ideas what to look for?