A leaking nail gun can be caused by several things. Paslode’s are prone to cap leaks, from the seals in the valve in the cap being worn or from having grit and sand in the gun.
Duo-fast nailers, esp. the CN325 and CN350 models are known for their triggers leaking. Two little O-rings in the trigger is this gun’s weakest link. Other than that they are built like a rocks.
I sell a wide assortment of O-ring s for nail guns, my ebay listing are below, if you don’t see what you need feel free to contact me at email@example.com (please use a nailgun o-ring related subject so i don’t send it to the spam folder)