Wildcat MK3 (not bottle) tuning question

[Pauly5]

I recently bought a sub 12 W/cat mk3, .22. I am going to use this for shooting feral pigeons around buildings and inside warehouses, so I want the power around 10 fpe.
It had been tuned previously to it's max potential of about 20 fpe, so I set the reg back down to about 55 /60 bar. Now when I turn the hammer wheel from 1 upwards to 7 the power decreases from around 13 fpe down to about 5 fpe. Shouldn't it work the other way around? When at the higher power the power increased when turning from 1 to 7.

I thought it might not increase, but didn't think it would decrease. Any advice welcome. Thanks.

 

[EDventure]

I'm no expert but wonder if the internal hammer spring screw is turned out too far. My guess is the hammer is hitting too hard causing the valve to stay open too long.

 

[ladwict]

Get a 1.5 mm hex and turn the hammerspring adjuster (through little hole in powerwheel set at the bottom, 6’ clock) clockwise ( lower tension) a few turns then check again What happens. If you still see velocity hoing down with higher number do this agian till the process flips around .

be careful that you don’t check speed when hole in wheel is at the bottom. ( speed will be at its lowest)

 

[CoyoteGod]

Always want to find your maximum possible speed on the reg pressure you pick on hammer spring setting #7. If you are getting 13 pounds on #1 just means the last person to do the tune sent the tune on hammer spring selection #1 not #7 or when you decreased the reg pressure, the hammer spring got really out of alignment, which its probably the case. Adding more hammer by going up on the dial would most certainly cause your speed to decrease. Redo the tune on #7 being your max speed for the 10FPE, so your power and speed decreases all the way to #1. Should be about 100 FPS in decrease FPS from 7 to 1 on a good tune. I have found on non sub 12 WC rifles that hammer is best about 6.20-6.25mm on the stock spring. That is going to be way different on sub 12. Measure you current hammer depth for sure to get a baseline. You want to do this same thing on your final tune also so you can replicate it and check the accuracy of your hammer from time to time to see if your hammer spring screw backs out. Hammer can be sensitive at the max speed depth, turns of 1/8th turn are significant. Take your time, two or three turns could potentially take you way off course.

 

[Pauly5]

I'm no expert but wonder if the internal hammer spring screw is turned out too far. My guess is the hammer is hitting too hard causing the valve to stay open too long.

I did wonder if this might be happening. I just didn't think the speed would decrease so much.
So i'll wind the screw in a lot more and base the tuning off setting 6 or 7, then wind out screw until speed reaches "the knee" plateau.

Coyotegod, is that measurement the length of the adjustment screw sticking out of the spring seat?

Out of interest, what sort of reg setting are the sub 12 ones set at? (Assuming the reg gauge is reading correct)

 

[ladwict]

When you base your most used tuning on a middle setting you have space to go up and down with the power wheel.
you cannot wind any screw to the knee if you do not check the plateau first.
Do you have any clue of pcp tuning ? maybe ask for help from the very beginning /basic essentials of the process .

 

[CoyoteGod]

I did wonder if this might be happening. I just didn't think the speed would decrease so much.
So i'll wind the screw in a lot more and base the tuning off setting 6 or 7, then wind out screw until speed reaches "the knee" plateau.

Coyotegod, is that measurement the length of the adjustment screw sticking out of the spring seat?

Out of interest, what sort of reg setting are the sub 12 ones set at? (Assuming the reg gauge is reading correct)

Pauly

Under the wheel is a thimble type cap that goes over the spring with a grub screw sticking out of it. The grub screw is your hammer adjustment 1.5mm. Measure the hight of the grub from the thimble type cap to the top of the grub. This is your hammer value.

Also you can set your hammer on any wheel number you want. However, just be careful to not tune to max on a value under 6 or 7 or you will have FPS loss on #7 due to going pass your max hammer spring for your give regulator pressure. This is why FX recommends tuning to max FPS on 7, which is usually done at a hight FPS/FPE than wanted overall. I typically tune for lets say 910 at #7 and want 865 overall. This puts my sweet spot at #5, but I have room to move up in speed and power for a longer shot if ever needed. Also like to move down to 840s for closer shots. This is the nice thing about this type of set up from FX.

What Ernest Rowes wildcat tuning guide on YouTube. This is where I got my first impressions and tuning help. This will get you shooting well and the tune just about right, also help with a few small issues that you need to watch for, such as detent ball and spring position and operation. Don't lose these parts! Help you make sure you put the power wheel back on correctly after measuring and adjusting.

Sorry my friend, I am not sure on regulator pressure for sub 12, I think it will be a little bit of trial and error for you to get set up. Do you know what the regulator pressure what when you purchased it? This would be a good starting point. Even 5 PSI on a regulator makes a big difference in FPS.

Hope this helps! Take care and enjoy.

 

[qball]

to get to sun 12fpe with out the TP choke is a bit tricky.

Here is what I normally do:
1. Fist you need to find your minim HS preload, to do that you adjust in the HS preload until there is no different between 1 and 2 or the screw won’t even reach the wheel. Then you can increase till there is a little bit of difference to give you Tune-ability, you want the preload pin barely touching the wheel on lowest setting.

2. If you have a newer barrel there is a pellet port and slug port then use the pellet port

3. INCREASE your regulator pressure. Yes, increase!!! Leave the HS on 1 the. Increase the regulator till the speed drop to where you want it. With a 500mm barrel this might be up in the 140-150 range depending on the hammer weight but I suspect round 140 bars with factory 7 gram hammer weight.


Cool thing is as you increase HS on the wheel the speed jump is bigger so you can shoot multiple ammo quite easily. Fine tuning is done by the preload which is why you need to start with some/minimum contact as adjust reg pressure is very hard to do in fine increments. For example my crown shooting at 10 FPE with a shorter barrel which is easier has reg of 145 but the crown has heavier hammer. Another GREAT thing about this tune is it will be Uber quiet and efficient, all I hear is my hammer ping on my crown and on my Dreamline it’s just a clack.


Good luck.

 

[CoyoteGod]

to get to sun 12fpe with out the TP choke is a bit tricky.

Here is what I normally do:
1. Fist you need to find your minim HS preload, to do that you adjust in the HS preload until there is no different between 1 and 2 or the screw won’t even reach the wheel. Then you can increase till there is a little bit of difference to give you Tune-ability, you want the preload pin barely touching the wheel on lowest setting.

2. If you have a newer barrel there is a pellet port and slug port then use the pellet port

3. INCREASE your regulator pressure. Yes, increase!!! Leave the HS on 1 the. Increase the regulator till the speed drop to where you want it. With a 500mm barrel this might be up in the 140-150 range depending on the hammer weight but I suspect round 140 bars with factory 7 gram hammer weight.


Cool thing is as you increase HS on the wheel the speed jump is bigger so you can shoot multiple ammo quite easily. Fine tuning is done by the preload which is why you need to start with some/minimum contact as adjust reg pressure is very hard to do in fine increments. For example my crown shooting at 10 FPE with a shorter barrel which is easier has reg of 145 but the crown has heavier hammer. Another GREAT thing about this tune is it will be Uber quiet and efficient, all I hear is my hammer ping on my crown and on my Dreamline it’s just a clack.


Good luck.

This is great info as the sub 12 tune appears to be a lot different. I would have never thought of this bottom up type of tune, but makes sense for tying to detune an airgun that is made for lots of available power. What surprised me is the amount of reg pressure compared to relatively light hammer tension. Definitely closing the value super quick.

 

[Pauly5]

Thanks everyone, This is great info. Yes I have reasonable experience tuning.I've certainly read enough and watched plenty of videos. Whisky68 was probably my favourite and most helpful. I have a Mk2 impact shooting around the 908 fps mark, and it's just right. Sweet sound, and grouping on a thumbnail.

This W/C was a sub 12 from new for the previous owner, then tuned for it's max output, and so i'm not sure how high the reg will autually go, but I hadn't thought of having it set high for low power, and might try that. Would there be any difference in a reg in a sub 12 compared to FAC? I'm in New Zealand, so no issues going over 12 fpe by the way.

I wound the grub screw in last night, and it's made all the difference as it was so far out I could feel it poking my shoulder!! I have found the point where it stops increasing speed, then backed it off about 5% of that, so now it's where I want on setting 3. Next I will shoot some groups, and see if I need to tweak that speed to get good groups.

 

[qball]

What we have is FAC guns or components made for power. Factory sub12 guns have factory parts restricting power like very small plenum, very tiny TP and even lighter hammer and spring and regulator tuned for lower setting or bigger delta between tank and plenum.

Only way to get a FAC gun with long barrels to shoot well under 12fpe is to increase reg pressure so the hammer can’t open the valve. It is not as consistent as a physically choked down gun but the benefit of that is the ability to tune up the power with a dial. Keep in mind that reg creep will be more obvious but just dry fire to scrub first shot or two.