Bobcat MKII .25 hammer spring adjustment

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cj_86

cj_86

Member
Jul 3, 2015
311
40
Illinois, United States
Has anyone ever bottomed out their Bobcat hammer spring screw? My Bobcat avg. fps was 874 fps ,but I started to tinker with the hammer spring screw and gave it a full turn in a clockwise rotation. I'm now getting 917fps and by the looks inside of the valve block, I think I can turn that screw clockwise 2-3 more turns. My curiosity is trying to get the best of me and I really want to crank her up more!! So would it hurt the valve? FYI regulator is still stock 140BAR.
CJ
 
I have the FX Bobcat .25 MKl unregulated. The gun shoots jsb kings at 915 average and jsb mkll king heavies at 815 fps average. That is my guns limit at operating within a 15 fps extreme spread with 30 shots. It will turn in more but the gun gets wild with air use and fps spread can vary by 20 between shots. The fps did go as high as 950 with the kings. You have internal regulator so maybe it will keep the gun operating smooth at the higher numbers. As for damage, I turned in till the gun did not respond with increase in spring pressure then backed off. No problems noted.
 
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Well I did a shot string and was disappointed to find that my fps is not at 890-900 where I set it last night and it is now down to 845-850. I was having a hard time setting the hammer spring screw with loctite and what I did I turned it in 2 extra turns, applied loctite, and turned it back out 2 turns so the loctite can get between the threads if that makes sense? I don't normally apply loctite this way but that screw is so thin that applying loctite the "normal" way didn't work for me.

I also cleaned the barrel when I was done because accuracy was dropping off and I'm not sure if that had an effect on fps going down? 

Anyways, I can investigate later and here is the shot string starting at 200 BAR fill:

846.6
844.3
849.5
852.3
844.7
853.2
847.0
843.6
850.6
851.7
844.8
846.3
844.2
845.5
844.4
836.5
840.6
847.1
837.7
848.2

 
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Ok thanks for that shot string information.I notice my gun always settles down a bit after an adjustment also. Your range accuracy is probably there just shaking from all that pumping. Builds character also. Ha Ha. Well that string looks good and stable. Im sure you could put a half turn on there and get her up some but it looks fine. Seems we always want all the gun can do! I lowered the avian pest population here at my neighbors farm today testing heavies. They seem to have same accuracy as my lighter kings, both cut each others holes at 25y and 1/2"-5/8" group at 50y in a 5mph wind. I just love the energy at range. It is wide open for long shots here in NC foot hills. Dont know about you but I am 13 again with my air rifle in hand. Enjoy the BC, it's one of many great PCP's. Any questions you might have just hit me up, I will let you know anything i have learned shooting mine for the last year and couple months. This gun is a joy to shoot and plan on shooting it for a long while.
 
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*The receiver needs to be removed from the stock to expose the hammer tension screw. Please make sure your air cylinder has an internal check valve before you try to spin it off.

The screw is the one with a hole for a 5mm hex key and I did not need to heat screw to break the loctite. Turn clockwise to increase hammer tension and before you turn the screw make sure the hammer is all the way forward to relieve tension from the spring.


I tried using a paste type loctite ,but it would squeeze out when turning the screw in.


I found that a liquid type loctite worked much better when applied to the screw.

 
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