Seem to have misunderstood the question, sorry. If the valve's been sitting for a while I'd put some oil in the the air intake and on/off pin and let it cycle through for like 50 shots or so. Assuming that doesn't fix the problem you may have a bad match for O-rings for your bolt stem and I'd check those. If the bolt is sticking foreword it's likely not resetting properly, if it's just blow through air I'd look at replacing some O-rings in the front half. Honestly though, having picked up mags that have sat in garages for 10 years and oiled them before firing, it's unlikely that there is an o-ring problem here.