Unfortunately the factory guns are rarely set up to operate at their maximum efficiency, but it has to be born in mind they are mass produced factory units.
Using the standard gun around four to five mags on a carbine is normal and eight to ten on a full length. This can be extended by correct tuning but it's limited, the .177KT being the least air efficient and the .22 full length the most.
Once you start upgrading parts it opens up a whole new world and I've managed 260 shots from a fully modded .20 full length.