Very common problem with the CN350 and CN325 nail guns. I sell kits for these guns on ebay CN350 leaking trigger and here. Duo-Fast CN350 O-ring + Cylinder Seal CN-220-3CN350 O-ring Kit + Cylinder Seal #cn-220-3 Schematic + O-ring Reference SheetAvailable Qty: 9 Post navigation DUO-FAST CN350 O-RING KIT Duo-Fast CN350B