I just wanted to mention that with most (if not all) of the norinco m14s/m305 rifles out there, extraction of the spent round is usually 45 degrees upwards. You may want to design a stock that keeps the port a little more open.
When most people get stovepipes, the brass hits the scope mount and it rebounds back into the action.
Or I may not have the faintest idea whatsoever of what I am talking about. YMMV