With the model 310 you need to turn the safety off, open the bolt, squeeze and hold the trigger fully then slide the bolt rearward. Make sure the bolt is completely out of the receiver before you let the trigger return.
Mine is a little temperamental and I need to work the bolt a little while holding the trigger. It seems that some of them don't disengage the catch completely and you need to coax it out. I have also heard of a few that need to be dry fired (firing pin released) before they will come out.
Just remember DON'T FORCE IT!!