In a long post further down the list on lightening a Quattro trigger pull, "Flyer" said, The Quattro trigger from Hatsan (the one that interests you and not the previous trigger designs) is a real great step forward for low budget air rifles but some of the details of its design are not as they should be in the first place for reasons beyond our knowledge. It is supposed to be a close copy of the CD trigger group found on Air Arms air rifles but it has not the same quality of execution or precise "feeling" for the user. You guessed right, the small spring at the bottom right of the mechanism and its tension is merely responsible for the regulation of the trigger blade pressure. By screwing or unscrewing the adjusting bolt you alter the tension of this spring (anti-clockwise movement of the allen bolt = less tension to the spring leading to lower trigger pull pressure). Until here everything seems OK. But this is not true. The real problem lies in the angles of the sears just as they are designed and made from the factory. The result? After a low pressure first stage you end up to VERY HEAVY second one - no matter what you try with lubing, adjusting etc. That is because the No 3 sear (from top to bottom) engages to the No 2 in a continuously changing manner - the contact surfaces (polished already from the factory) are connecting with the wrong way. Check on a diagram of a Weihrauch Rekord trigger group or an Air Arms CD unit and you will be able to spot the difference. The sear No 3 (sorry for not being familiar with the real terms in English) has a noticable "step" or "protrusion" or "bulge" at the upper end (lacking the right radius) which forces the trigger blade to push the sear No 3 against the sear No 2 (backwards - contrary to the pressure of the already cocked mechanism) ending to a unpredictable and not so stable trigger release. It is something similar to the event taking place inside a box-lock trigger of a traditional English shotgun (classic Anson & Deeley patent) - the trigger becomes heavier as it reaches the let-off point. This works well of course as an extra safety feature in a shotgun (the geometry of the mechanism is responsible for that) - but here we are dealing with rifled barrels, pellets and ultimate precision possible. My advice is to let it as it is for now and search for a good airgun gunsmith (a real expert) who will know what to do and what not to do in a trigger. It may cost something more but the job will be done in the best possible way for you and for the gun.MY question is what should the two sears mating surfaces look like ? What is The shape you feel they should be?