Tuning Actual vs. advertised power for FX Wildcat mkIII Compact .25

[markc_66]

I have the same gun, .25 compact. My screws came loose on the probe as well not too long after I received it. I could only guesstimate where the original location was by the indents from the screws. Is there a more specific way to adjust accurately? Out of the box my shots are all over the place. I have not adjusted anything. Here’s an example with pw on 7 and factory reg setting around 140 I think, the stock gauge really sucks because the markings on the scale. I have bought a better huma gauge for it, but have not installed it yet so I can get a more accurate, reg pressure reading. Do you have any advice for me to tighten up the strings? I am a bit of a newbie but I have watched a ton of tuning videos. Just haven’t tried it yet.
These are with 25,4 g jsb diablos.

Shot count: 13
Low: 745
Hi: 884
Avg: 850
Spread: 139
STD Dev: 35.7
745
844
868
849
844
856
872
868
868
872
884
819
858

 

[swopever]

Are you talking about the two grub screws on the cocking arm? But yes, they also control pellet probe depth. Putting them at the indents is usually a good way. Watch Ernest Rowe's video "FX Wildcat MKIII Reassembly - FX Masterclass" on youtube as he explains what to measure and adjust.

Once you have pellet probe returning to correct spot each time you can adjust hammer spring to tighten up your velocity STDEV.

BTW I'm the original poster of this thread. Two biggest problems I had were 1) those grub screws coming loose and 2) after installing Huma reg gauge realizing the FX gauge was reading 10 bar lower. See my earlier posts in this thread for other upgrades.

With reg set at true 150 bar (instead of 140 bar with FX gauge) I now shoot 56 FPE, with 0.37 inch groups at 50 yards. Although my accuracy is fine, the regulator consistency is not impressive, with about a 15 psi spread and STDEV around 8. Others show STDEV of 2 or 3, I've never come close to that.

good luck

 

[Quad82]

I have my .25 MKlll Sniper shooting 2+ mags with a H912, L888 AV 896. I am at 59 fpe now with 50 cent size groups at 100 and most shots touching at 50 yards. I had it tuned to 71 fpe using the JSB heavy’s. It still held fair groups. But shot count really suffered.
My set-up is : 33.5 NSA slugs, 250 bar fill, reg at 145, HS 3.7mm, PW7, heavy hammer and plenum extension. First mag runs 250 down to 180 bar and the second mag from 180 down to 145 and then falls off the reg for a couple extra shots.

 

[Cran]

Well, here is the first installment on the journey.

Previously I had changed the barrel for my WC MK3 BT VP to a 500mm .25 cal barrel. I also switched out the aluminum bottle for a 480cc CF bottle and replaced the .22 cal pellet probe with a Huma .25 cal pin probe. This gave me 863 FPS (42 FPE) with the FX 25.4 grain pellets with the reg at 100 bar. Not particularly impressive. I raised the reg to approx 110 bar and the velocity dropped to 763 FPS! Obviously, the reg pressure was too much for the hammer so the valve was not opening enough.

Today, I made the following changes (1) Maxed out the hammer spring adjuster and, (2) Installed the hammer weight from the FX Wildcat/Maverick Slug Power kit. After reassembling I tried to raise the reg pressure some more. Nothing doing, it wouldn’t change! The velocity did increase however, back to about 870 FPS. At this point I should mention that my 500mm barrel has the old style Transfer Port with a single round hole.

OK. Obviously I have a reg setting problem, so I need to determine the 1st reg pressure. Imagine my surprise when I turn the screw for the second reg counter clockwise a couple of turns and the reg pressure on the gauge doesn’t change.Could it be? Yes, the 1st reg was set at an incredibly low pressure, probably 110 Bar. So, now I need to take the stock off so that I can adjust the first reg.

As I increase the first reg oressure (counter-clockwise) I hear the telltale hiss, and the pressure gauge starts to rise. I raise the 1st reg to about 160 Bar. (Did I mention that my next purchase will be a decent gauge - probably a Huma/Wika - so that I can actually read the damn thing). Then I degas by removing the bottle, dry fire and listen to the air bleed out of the plenum until the gauge reads zero. Next I turn the second regulator screw clockwise until I feel some resistance. Then I go back counter clockwise for a half turn or so. Screw back on the bottle and, voila, my second reg reads about 40 bar. I then adjusted the second reg up to approximately 130 bar and now, finally I am good to go for the moment of truth.

The results are interesting!

FX 25.4 grain pellets; 1st Reg 160 Bar; 2nd Reg 130 Bar; Hammer adjustment maxed.

HW Shots High Low Avg FPE ES SD

Wildcat MK3 BT Compact 7 12 984 979 982 54.4 0.5% 2.1

Wildcat MK3 BT Compact 6 10 995 984 989 55.2 1.1% 3.8

Observations:

(1) Obviously the gun had been set up with a very strange tune from Utah Airguns, one that was clearly set to maximize shot count and not power, or not even to really utilize the benefits of the new BT dual regulator/large plenum setup

(2) The new tune is not complete. The fact that I get a higher FPS from position 6 than from position 7 show that the Valve is slamming closed on P7. This I either need to adjust the hammer spring adjuster downwards a bit, or raise the reg pressure some more. In any event I’ll play with it until I get a nice (downward) FPS gradient when I change the wheel from 7 to 6 to 5…

(3) The gun is a little louder now, but not a material difference to my ears.

(4) I should have no trouble getting well over 60 (and probably over 63) FPE when I use 34 grain pellets. I might also get some gain from switching the Transfer Port out with a Huma slug port.

That’s it for tonight. Tomorrow I will shoot the 34 grain pellets to see what kind of power I get. If I am still not getting a gradient on the wheel as i go down from 7 to 6 to 5 I’ll either adjust the hammer spring preload down a little or raise the reg pressure a bit, so that position 7 is indeed the highest.