I bought a Duo-Fast CN325 about 1 year ago on Ebay. It was an older model. The color of it is Gray. The person I bought it from said he replaced all o-rings and said it works. I bought some nails for it about 3 weeks ago and found out that it is firing 2-3 nails at once. Sometimes a nail doesn't fire all the wayinto the wood, I have to yank and pull on the nailer to get the nail out of the nailer. Is there anyway that I can adjust the nailer to shoot 1 nail at a time?