What bar to set a Huma reg for a .25 Wildcat

What is your WC shooting at now with the regulator at it's present setting?

optimal preassure for wildcat shooting 25.4 kings is something between 130-140bar

The WC 25 I had with Huma set at 150 shot the Kings at 953fps avg. I would say try 130 bar and go from there. You'll need a chronograph to tune the hammer spring tension.

Just to let you know where I got the 130 figure from:

When I had my reg set at 155bar, it shot the 34gr pellets at 880fps. When I backed it down to 150bar, it went down to 848fps....so 30fps.

If you go by that, stepping down by 5 bar four more times, you get roughly 720fps from a 34gr.

Generally speaking, the 25gr pellet shoots 100fps faster, so maybe it would be around 820fps.

So it's a toss up if you choose to start at 130 bar or 135 bar. You'll need to go through the hammer spring adjustment procedure with each new reg setting.

Also remember that each time you remove and reinstall the reg, you have to set/check the bolt/pellet probe depth. IIRC, it needs to fall between 28.5and 28.75mm.

Let us know if you need any help with doing that okay?

Let us know if you have any questions at all. It's not a difficult job but easy to screw up if you rush or don't do exactly what needs to be done.

Here are some pics of when I did it.

This was my probe depth the last time I set it.



This was how the air cylinder came off.



The Huma next to the factory reg.



The receiver all cleaned up and ready for reinstall of hammer spring and nut.

So sorry, I can't answer in detail right now as I'm headed for work. Hopefully someone will chime in for you, otherwise I'll answer in depth when I get home this afternoon.

Thanks Bob. I'm a little confused on a few points. I set the reg to 145, removed the air tube and installed the Huma. It's back together and holding air. 

1. How do I know if I need to adjust the hammer spring? In other words, what's the correlation between the reg bar and hammer spring? I have a chrono and would like to be around 850fps for 25g JSBs.

2. You said if you "remove and reinstall the reg, you have to set/check the bolt/pellet probe depth". Did you mean hammer spring? Is your 28.64mm measurement, the distance from the back of the block when action is closed? (Mine is measuring at 28.65)

3. Does just adjusting the hammer spring require adjustment of the probe?

4. I read one post that said you had to loosen/remove a small allen screw to adjust the hammer spring. I just don't to damage anything.

Thanks for the support!

Click to expand...

1. The hammer spring tension should be adjusted to determine max velocity. This most likely will be different for any given reg pressure. You can then back out the hammer spring nut for a lower velocity if you choose. But the "system" will be more efficient with a properly adjusted hammer spring tension. Normally this is measured by how many turns inward the hammer spring nut is. My guess is at 145bar, you would be around 7 1/2 turns in for the velocity you want, but that would need to be verified with a chronograph.

2. When you removed the air cylinder, the frame position might have been disturbed from it's original position. If so, the probe depth could be off. If your measurement is 28.65, then there's no need to change it.

3. The hammer spring adjustment is separate from the probe depth. Once you have the probed depth set and the frame clamps tightened, it shouldn't change.

4. In my last pic, the largest hole contains the hammer and spring, which are under a nut. It should have an allen head shaped hole. Most likely the the nut is threadlocked in and needs to be heated up before attempting to removed the nut.

I used a micro torch but didn't heat it up enough and it stripped out. I was then forced to use an easy-out to remove the nut. It still required me to heat it up two more times before the threadlocker was soft enough for me to back the nut out. What I learned from this was I didn't get it hot enough the first two times. The third time I got held the torch on the nut until it just started to glow, and then it could be loosened.

My tip for you is to use a micro torch (fine pointed flame), and in a dimly lit work space, heat it until is starts to glow (not red hot) and then try the allen wrench.....hopefully it won't strip out. Make sure the flame is on the nut and not the receiver. The quicker you can work the better, as the receiver will act as a heat sink and absorb the heat. The longer you use the torch, the more heat will will be transferred to the receiver. The receiver will get warm, but you want to make sure it doesn't get hot. Also, what I did was hold the receiver with the rear tipped up slightly, this way the direct heat and smoke won't travel upward toward area of the valve.

Here's the thread from my install. I'll also try to find the discussion where CHUCK and others described the hammer spring adjustment procedure.

https://www.airgunnation.com/topic/fx-wildcat-25-mkii-huma-regulator-is-here/

Bob_O,

re: your point #2– would it possible to “witness mark” the frame and air cylinder before removal and reinstall to align the marks? This would eliminate the need to measure the probe depth?

tnx,

Matt

I suppose that's not a terrible idea. But needs to be precise as the range of depth is only 0.25mm.

The specs for probe depth might be between 28.55 and 28.8. Let me see if I can find the thread with that information as well as steps for adjusting the hammer spring.

Here's a post on setting reg pressure and hammer spring tension.

https://www.airgunnation.com/topic/setting-the-regulator-hammer-spring-tension-correctly/#post-222976

Bob, question for you...

The Huma goes in backwards compared to the factory reg. Does it take up less space in the air cylinder? Like would you get an extra 5 shots from installing the Huma, as there is more volume available? 

My WCII is new, so I don't really want to fiddle with the internals until I need to.

I don't know if shot count goes up as I had mine set for higher power over factory....so my shot count was much less. 53 ft.lbs. I think is what I got.....shot count was in the low 30's.

That's worse than my new S510 XS, GB.

If it were me, I go down to 130 bar and see if the ES gets smaller after adjusting HS tension for max velocity at that pressure.

You had some pretty hefty dips and recovery in velocity there from one shot to the next.

Something is going on. Especially with a nice regulator, you shouldn't have an ES like that.

I always got into the habit of burning off the first three shots (dry fire) after a fill. Have you tried that before going over the chrono? You'll hear a difference between the first, second and thirds shots as the gun comes up to pressure.

You're shooting 25.4's? Your goal is 840 fps? Ideal spread would be 2-3% aka 17-25 fps? 



135 bar would be just fine IMO. I don't think burning the first shot to eliminate creep will help your strings based on what I see..



Either regulator needs to break in OR you have variation elsewhere in the gun, ie: hammer + area it rides may need cleaning + lubed with MFG recommended lubricant, generally pcp hammers run 100% dry with no lube or with dry-graphite. Certainly wouldn't hurt to go over that area so you can check it off on your process of elimination. Most erratic variations in extreme spread are caused by hammer inconsistencies, but regulators themselves can cause this...



Have you tested any groups to see if its grouping decent with the exception of some vertical stringing from erratic velocities to eliminate possible clipping or poor pellet seating depths?



Hope you figure it out!