I have a Volmer HK21 that I just got, and I have not fired it yet. However, I was checking functionality and everything seemed to be working fine. I disassembled it to clean and put it back together and now it is very difficult to pull the cocking handle back now. Its as if the bolt is locked in the chamber and takes a good wack to pull it back. It was working fine so not sure what I did wrong. Any suggestions would be helpful.