I own a hatsan 70 in .25 and a hatsan 900 x in .22 which a moderated striker. Now the 70 has a Quattro trigger and loves jsb, gave it a polish relube and ptfe piston sleeve, shoots spot on, only cost £90 new but had to wait 6months for it!!!
If you don't want the wait my 900x aka striker, is also a good gun after a fettle including tbt kit fitted, and piston sleeve, trigger bit creepy but better after fitting a longer trigger adjustment screw, but no where near a Quattro.
I've owned several hatsan's never had a problem with them, just don't expect deep blueing.