I have just got a secondhand bsa ultra se multishot .177 and i have been struggling to find what pellets it likes so i went out this morning and bought half a dozen tins of various makes to try , i got round to trying the falcon accuracy plus and after shooting a couple of them the bolt has somehow got stuck in the fully closed position and wont move more than a couple of mm either forward or back , is there anyway i could free this off myself or will it have to go to a gunsmith ?