I have the same gun, bought it about 3 months ago. I haven't had any problems with mine yet, no misfires. The barrel selector only selects which barrel will fire first. When you pull the trigger the first time it fires whichever barrel is selected. Release the trigger fully and pull again to fire the second barrel. You have to release the trigger fully after the first shot to engage the second firing pin for the second shot. If you're holding the trigger part way in after the first shot, you're second shot won't fire.