WA gas mag (need help with mod)

[wantspliff]

hi peeps
i'll get straight to it..
on a WA gas mag, what does that lever do (the one that locks the outlet valve OPEN)
the only thing i can see it does is lock the valve open but why??
i ask as ive always wondered if i could just take it off, seeing as my GHK Co2 mag doesnt even have one
can anyone shed some light on what its actuly for and if i can just take them off??
thanks for any help