Hatsan BT65 .25cal - hammer spring adjustment

[skiron]

Hello everyone

It seems that I need your help with this.........(newbie speaking!)
I recently became the owner of a BT65 6,35mm caliber. My riffle, right out of the box, in my initial testing was shooting H&N Grizzlys 31g @900fps max...
Wanting to increase the velocity of Grizzlys, I tried to tune the hummer spring by rotating it clockwise to increase power.

The problem is that, after 3 CW turns, the complete cocking becomes immpossible, and it seems like the bolt can't travel further back to cock, in other words, feeling like the spring is completely compressed! With only 2 to 3 turns, cocking is ok... harder than before, but ok......but even with half a CW turn more, let's say 3,5 turns, the bolt can't come back fully to cock in no way....! the bolt-cocking stops just before complete travelling back, and whatever power i'm puting to cock it completely, it's impossible. So, I have make only 3 turns CW in the hammer spring, even if the hammer spring back screw has more CW turns left...

With these 3 turns CW, Grizzlys shoot at 930fps average right now, but i need some more.....

Is these 3 turns the maximum turns I can use in order to cock it, even if the hammer spring takes more turns, or something else is happening???

thank you in advance,
Argyris

[Tiroflojo]

Greetings.
     I do not think it possible that with only three turns of the hammer's tensioning screw the spring is fully compressed and the trigger mechanism can not be mounted. It takes at least 8/9 turns to reach the tension stop. screw turns but no longer tightens the spring but you get tight and mount the hammer despite this.
     It only occurs to me that the spring of your BT 65 is not original and in its place there is a very different one with thicker thread and more turns of turns.
  In the photo the right spring is the original, the other two have been mounted on the BT 65 to give more power: 65mm long, outer diameter between 12-13mm, and thicker thread. But the same amount of laps.

[skiron]

Big thanks for your help

Yes, for me 2, I should be able to make more than 3 turns, without the cocking to be impossible in these final cm of it's travel....:/

However, the riffle came right from the factory....so the hammer spring must be the original one...the riffle is new, and i bought it from the official Greek Hatsan dealer 2 weeks ago...

I still can't imagine (neither have the knowledge) and find what goes wrong and cannot cock the gun completelly when I proceed with more than 3 CW turns in the hammer spring screw......i placed all of my force to cock it completelly, but with no luck obviously....

Right now, going from factory settings to xtra 3 turns CW, it now shouts at about 60FPE at the muzzle, with H/N grizzlys 31grain @930fps....and 25,39g JSBs somewhere near 1050fps......Just to help you understand and tell me if I have already reach the maximum spring tension/power with these specific grains....(tuning only the spring turns of course)

[Tiroflojo]

In fact your BT 65 with that power is already at the limit of its possibilities. The original spring is already at the top of its tension. And it will be possible to remove turns in the tensioning screw but not put more.

[skiron]

Thank you....I believe you re right and i'll trust your experience in this...so maybe I have already reach the maximum spring tension and thats the reason I cant cock the gun with more than these 3 turns...even if the screw still turning further

The reason I was confused, is because in many reviews and posts I ve read, users seam to be able to make more than 3 cw turns...even 6 or 8...and I couldnt understand why in my riffle the cocking after just 3 turns was impossible. I think that all I had to ask is whats the maximum velocity a .25cal  bt65 can reach with jsbs 25,39grain by tuning inly the hsmmer spring, to understand if I have already reach max tension with these 3 turns I did...