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Thread: Hatsan AT44 trigger tuning

  1. #1
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    Default Hatsan AT44 trigger tuning

    This summer I bought Hatsan AT-44 10S(W), a 4,5mm 10 shot turkish PCP gun with walnut stock.



    In general, it turned out to be a good gun, especially if you keep in mind the price/quality relationship. What I liked the most was that the main specifications of this gun were exactly like the manufacturer advertised – 320m/s with light (0,5g pellet) and 50 full power shots from 195 to 100 bar. By the way compared to my other airguns, this was the second one that met the manufacturer’s specifications right out of the box. Fox example Weihrauch HW77k was advertised as 290m/s, really it was 260m/s with 0,51g pellet.
    Not only the power of AT44 was good but the plateau was in place, the rifling and crown of the barrel were acceptable and the iron sight (actually plastic but a good one) was factory adjusted on target. The overall finish of metal and wooden parts was not exceptional but quite acceptable. The gun performed 15mm ctc10-shot group in ideal conditions at 25m if the shooter was capable.
    But there was a catch – the awful trigger. The trigger blade looked golden and decorative but the performance of the mechanism was the worst I had ever experienced on a PCP gun. If compared to say the same HW77 trigger, the springer's trigger outperformed the AT44 trigger by far. AT44’s trigger was hard but not constantly, sometimes hard, sometimes not so, sometimes so hard that you started to think that you forgot safety on a wrong position. And the hard trigger was combined by a creep, an unconstant creep. Very seldom it was no creep, usually creep-creep, sometimes creep-creep-creep. All this made the shooting of this gun a headache, sometimes the trigger was so hard, that you had to fire a shot into air, reload and hope that this time the trigger performed better.
    I am not a tinkering type, I only repair something when that is inevitable, but something had to be done with this trigger. Looking for information in internet was not very productive, you could find out that the trigger problem of AT44 was quite usual and it could be overcome with not so much trouble, even some pictures were available plus couple of videos in an unknown language (turkish? romanian?). But I was not able to find any explanation how the trigger mechanism worked, not instructions how to disassemble it and what exactly to do. So I had to figure it out all by myself and here are the results. I use here my own arbitrary numbering system, in the end there are the part numbers by Hatsan.



    Trigger dynamics

    1. When cocked, hammer passes partially sear 1, pushes it upward and locks behind its front concave,
    2. pressing trigger blade, its back (E) presses on sear 3 (at A) and the last one presses on sear 2 (at B) ,
    3. this forces working surface (C) of sear 2 to slide downwards on working surface (D) of sear 1 and release it,
    4. the front concave of sear 1 turns downwards forced by spring (6) and releases the hammer.





    Spring 5 is needed to return sear 2 to its initial position to make it lock at sear 1 on cocking.
    Spring 8 returns the trigger blade.
    These 2 springs plus sear pull down spring 6 are essential for trigger mechanism to function.
    To make trigger lighter springs 5 and 8 could be changed by softer ones, e.g. a ballpoint pen spring cut in half would do.
    All trigger pull adjustment details (11-15) are only meant to make the releasing of a shot harder and could all be discarded.







    The safety detail 1 blocks upward movement of sear 3 and so makes the release of the hammer impossible. When the safety is on "FIRE" this detail does not interfere the action of trigger mechanism in any way. Keep the safety mechanism intact!

    Removal of the trigger mechanism:







    1. Just push out pins marked with red arrows. This need not much force, these pins are embedded in plastic body.
    Warning. After you have removed the trigger mechanism from its plastic bed, be careful with safety SAFE/FIRE switch (S). It moves between two positions quite loosely, locked onto these positions with the help of a spring and a plastic ball. Pulling it carelessly, you could pull it out and loose the ball and spring. To put these details back is very tricky without complete disassembly of the gun.
    2. Push out pins in trigger case. First push out pins holding springs at place, do not lose the springs. Most of these pins have grooves in one end, push the grooved end out.
    To make the trigger smoother, working surfaces (C) and (D) of sear 2 and 1 should be polished as well as inner surface of trigger case should be cleaned of casting defects and the trigger pull adjustment screw (11), spring and other accompanying details should be removed. Changing springs controlling trigger blade and sear 2 movement with lighter/softer ones would make trigger lighter too. So really this trigger is a one stage trigger, the first stage is mimicked by trigger blade spring and there is no possibility to regulate the sliding distance of surfaces (C) and (D). The last is normally used for trigger pull adjustment - longer distance more pull, shorter distance less pull. Pull adjustment by restricting trigger details movement by increasing spring tension is plainly stupid to say the least.



    It is very difficult to totally remove the creep of a trigger of this construction. The critical parts move tightly between walls of trigger case and their sharp edges (e.g. edges and corners of working surfaces of sear 2 and 1) tend to scratch on these walls. Very careful polishing of these edges could cure the situation a bit. Moving surfaces of trigger mechanism should be lubricated quite sufficiently with some molybden containing grease.

    I cannot advice to do this, but I like very light trigger, so I added 0,15mm thick bronze sheet between sears 3 and 2 (at location B) as increasing this distance makes sliding distance of surfaces (C) and (D) shorter. The sheet was fixed using the same trigger pull adjustment screw, but it was screwed in sear 3 from other side. Resulting trigger pull was about 50g and no creep at all.

    Happy tinkering
    A.M.
    17.10.2010

    Hatsan AT44-10 series (10-shot models) Exploded View (revision:June2009)

    102 - sear spring (5)*
    103 - sear 1 (2)
    104 - sear 2 (3)
    105 - sear 3 (4)
    106 - sear 3 spring (6)
    107 - trigger case (10)
    108 - trigger connection pin
    109 - trigger travel spring (8)
    110 – trigger (9)
    113 - trigger pull adjustment screw (11)
    111 - trigger travel screw (7)
    112 - trigger pin
    114 - trigger pull adjustment bush (12)
    115 - trigger pull adjustment locking spring (13)
    116 - spring cleat (14)
    117 - trigger pull adjustment spring (15)

    411 - safety sheetmetal (1)

    * - in parenthesis are arbitrary numbers I used in this paper
    Last edited by A.M.; 19-10-10 at 23:14.
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  2. #2
    Sharp Shooter

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    That's good stuff, did not read all , not being a Hatsan owner , but there where some questions here recently around them ,and this should serve well.'

    Thank you
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  3. #3
    Protea FT Team '12

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    Some great info. I'm gonna put this in our Technical referance section.
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  4. #4
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    Great Info!
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  5. #5
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    Day and night difference on the trigger, thanks for the information!
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  6. #6
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    once upon a time, i have changed the springs and trigger was very smooth but there was a problem. rifle was firing itself. it is dangerous.
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  7. #7
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    Quote Originally Posted by madmax View Post
    once upon a time, i have changed the springs and trigger was very smooth but there was a problem. rifle was firing itself. it is dangerous.
    That is correct, tinkering with trigger mechanism could be dangerous. There is one Estonian proverb: "ten times measure, on time cut".
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  8. #8
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    I only removed the pressure adjustment spring at the rear and shortened the spring on the trigger blade a little. I did not polish Sears 1 and 2 and only polished the sides on sear 3. I have tested the safety as well as trigger release. All seems fine at this stage, but thanks for the warning. I have kept all the springs and bushes, so replacement will be quick in case it is necessary.
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