IMHO the only battle rifle to have a " valve " is a FAL . And it only has a " valve in the sense that it is " over ported " and you most likely should restrict the port thro the crude " screw down " appliance that is provided . Some rifles may have a gas cutoff switch where all the gas goes out the barrel to say launch grenades which shuts off the normal use of gas to run the action ( thereby using all for the propellent of the gernade ). With any sks you will likely see a gas port ( its not adjustable ) occluded by cos , fouling , a jacket piece , et all .... If you have a " gernade " switch in the gas system , well then clean and clear it . It is not a valve ( a valve regulates flow , its not an on and off thing ) . As an aside ill question your ammo . I have ... well nm cases of ammo that work , but strangly enought a bud just bought some " wolf " branded ammo that is a little light , and does not look right . It works in my sks(s) , but not his . Suffice it to say i got a bunch of this round nose crap now .