After running about 600 pellets through my new .25 125th. The breaking in period has little affect on accurancy and trigger pull resistance. I really believe the heavy non-adjustible quatro trigger(US version) pull had a lot to do with accuracy.
After reading an internet article on the quatro and how it functions i decided to take it apart and try to tune it. It only takes 3 fasteners to remove the rifle from the stock. Be careful some of the trigger pins are so loose they will fall out before you can take a mental or physical pic of how it looks assembled. There is one external spring and one internal spring that you need to take note of orientation.
After disassembling and cleaning all the parts and trigger housing bracket i proceded to do the following to all the trigger action parts.
1) Wet sand and polish with steel wool all sides and mating surfaces.
2) Clean with kerosene then soak in light weight synthetic motor oil
3) Reassemble all trigger components carefully after lubing with lithium grease
4) Add a dab of `Goop' to ends of all the triggger action pivot pins to keep them from falling out upon reassembly
5) Trigger modification, the (2) trigger adjustment socket head cap screws when bottomed out(when fully adjusted in) barely are exposed to make any trigger pull reduction difference, so i carefully mounted the trigger in my vise and removed about a 1/16" of trigger surface that the cap screws seat on with a coarse file. Be careful only take it down 1/16" this is all you'll need.
After careful reassembly and oiling, and a good barrel bore cleaning(& oiling) i ran a few rounds throught the gun and tried adjusting the 2 trigger screws.
HOLY SMOKES WHAT A DIFFERENCE. I now have an adjustible trigger! The lighter pull has improved my accuracy tremendusly. I can hit my targets in a free standing position with ease.
Removing that 1/16" of matl off the (2) cap screw trigger surface has made a huge difference!
Note: The trigger itself can be removed(by removing 1 pivot pin) and modified without going through cleaning up the other components like i did. I think it sure helped smooth out the action.
Reference article link: http://webcache.googleusercontent.com/search?q=cache:-IV6LJzI3Y8J:www.network54.com/Forum/79537/thread/1301669829/Hatsan%2BQuattro%2Btrigger%2B+hatsan+quattro+trigger&cd=6&hl=en&ct=clnk&gl=us