I have recently aquired my fathers cyrano 970 with a dry barrel kit (im not sure what kind) but anyway when I push the spear in a bit to test the presure sometimes when I let the spear go back out there is a very small hiss from the barrel for about 10 secs and then It stops, is this normal? I can get the gun serviced but i really would rather not also the gun was last used about a year ago and always was stored muzzel down.