I have recently upgraded my stock polycarbonate piston head with a SHS ergal silenced head, but I have noticed that the o ring the new head comes with is VERY loose. Is it for air seal purposes? I also noticed that it prevents the piston from falling out of the cylinder when turned vertically. After a few shots with the new head installed one of the teeth of the polycarbonate piston was quite worn down. What is the reason?