FX Wildcat .25 Cold Bore first shot POI change

[Grover]

Okay so over some time I have discovered the following. First shot over chronograph after sitting overnight on a 6 shot first shot average 993 fps / All succession shots average 856 fps. Also after letting the rifle sit 4-6 hours there is a jump up on first shots around 945fps all using 25 JSB's . I have played with the HST turned it in 3/4 turn and cold bore first shot is now only 3/4 inch of POI. I think the problem is a unreliable regulator causing my POI shifts. I got my new FX 600mm X- barrel from Utah air guns this past Friday. I took Hookster advice above. Ordered a Huma Reg awaiting for it arrive soon then will replace the regulator and put in new X barrel. Will post again later on the outcomes and performance after I tinker with tuning after install of new parts. Thanks for all of your input fellow shooters !! 

 

[nervoustrig]

Well I’m sorry that your gun has this problem but at least now you know what it is.

Remember when I said I was skeptical the velocity would climb all the way up to 1000fps? Haha, I stand corrected! Kudos on ChairGun for the prediction though.

 

[sonny]

just curious, could it be a oring leak at the reg?

 

[nervoustrig]

A leaking O-ring would just cause pressure loss to the atmosphere.

 

[Grover]

Will be taking it apart when new Huma Reg arrives. I have not had it apart as of yet. I don't think there is a O-ring leaking atmosphere as I can fill to 220 bar and after 4 days still at 220 bar if it had a bad O-ring. So I am pretty sure its just a Reg problem as nervoustrig said above. I will be taking the FX reg apart when I have it out see if there is a burr or some irregularity on any parts that would be causing the Creep!

 

[Nick47]

The new AMP Reg has some creep issues as well. FX needs to address this. Who manufactures the regulators for FX? And, what causes air to creep into firing chamber? Machining issue, O-ring issue or Spacer issue? Why does Huma, for example, not appear to have this issue? Makes me scratch my head.

 

[nervoustrig]

It has to do with how well the regulator piston mates to the valve seat. In an ideal world, as soon as the output pressure builds to the setpoint and the piston meets the seat, the flow of air would be instantaneously halted. In the real world, there are slight imperfections and air continues to weep through microscopic imperfections very slowly until the output pressure builds high enough to squeeze them together hard enough to completely halt the flow of air. It’s partly design and partly quality of workmanship. FWIW, I’ve had success with dressing the mating surfaces of a few different regulators. None were an FX however so I can’t comment on that.

 

[Grover]

Okay fellow followers I have gotten my new FX X-barrel and HUMA Regulator installed. Doing some final tuning. Was it worth it well I will give you the full report after I get a dry sunny day to shoot across chronograph. Had to order some new FX O-rings as I had a leak in related to damage to the front cap I had to remove. Just a preliminary short report had to adjust the reg pressure ordered a HUMA reg pressure tester well worth the investment 140 bar is too much for a .25 turned it down to 135 well lets just say holy crap less is more just need to play with the HST. Will have pics and full review of my project upgrade soon.

 

[xindaris]

Had a similar problem with my Wildcat but my first shot was low. Sent it to FX USA , they adjusted the hammer and regulator. Have not had a problem since.

 

[Grover]

Okay been a while since I have posted related to getting things in order. I have since gotten my 600 FX X barrel and put in HUMA regulator here is the following review. I have finally gotten time to tune and adjust the regulator and hammer spring to a Vel of 900fps. All of this was it worth it well I would say yes got a constant velocity along with great accuracy. I have posted a couple of pics of 65 & 70 yard target groups on early dead calm morning. The 70 yard was to the left as I adjusted the scope but I should have left it alone. No more POI shift on first shot.