The O ring will prevent a double feed. but as soon as the bolt moves forward it will push the ball past the detentes and the ball will roll strait out of the barrel.
Sorry for the confusion I miss read your original post.
You really are better off getting a better barrel. The stock one is WAY to big to be of much use.
WTB Mech CCM. S5, SS25, Works...
WTB Nickel PPS Stab, and Nickel/chrome ASA