Tuning FX wildcat mk3 bt softer valve spring to increase power?

bowopt said:

Hi,

I watch Matt Dubber's YouTube video about tuning for high power airgun.

He mentioned that he uses a weak valve spring in his 22 cal Impact Mk2 with very high reg pressure to achieve 70 fpe with 34 gr slug.

I wonder if we can use that same concept on our guns. In my case, changing the valve spring to a weaker spring, hoping that the valve will close faster on lower rear reg pressure and less hammer for my 22 cal wildcat mk3 bt to shoot 27 gr HP slug at 1000ish fps.

The current settings are 160 bar rear reg pressure and 12 gram hammer which makes the gun quite violent.

I'm hoping to use the 11 gram with weaker preload and lower the rear reg pressure, while having the weak valve spring to close the faster to get higher speed.

What do you guys think? Workable?

Click to expand...

How long is your barrel? I have a mii impact with the large plenum and 700mm barrel, with the reg at a 148b and I'm pushing 30gr javelins at 920fps. Maybe the weaker spring would require it onthe compact setup, but not sure that you'd need it even on the 600mm barrel

bowopt said:

I wonder if we can use that same concept on our guns. In my case, changing the valve spring to a weaker spring, hoping that the valve will close faster on lower rear reg pressure and less hammer

Click to expand...

A weaker valve spring will increase dwell (close the valve slower)

For whatever regulator setpoint and barrel length you’re using, it can help you achieve higher energy only if you are running out of hammer strike and can’t reach the velocity plateau. How can you know whether that is the situation? Incrementally increase hammer spring tension and check the velocity. If the velocity is continuing to increase when you run out of adjustment, a weaker valve spring may aid things. So would a heavier hammer and/or stronger hammer spring.

Can i ask why you need to shoot 1000 fps? My mav- same gun as yours shot 27.5 nsa to 930 with the stock hammer spring and a 10.5 gram hammer and i think only 112 bar reg. The trajectory is close enough to a 1000 that it really doesn’t matter and the gun was verry calm to shoot. Oh that was with a 700 mm barrel so you’d loose 40 or so fps @ 600 mm

bowopt said:

I maxed out the velocity at 1023 fps with 600mm barrel and 12 gram hammer with 160 bar reg.

The accuracy is pretty good at 1023 fps with hp slug 27 gr but the gun is violent.

I trying to think of a way to tame the gun by weaker hammer (11 gram), stock hammer spring and, perhaps, with the weaker valve spring. So that the valve will shut faster with 150 bar, hopefully retaining the 1000 plus fps with the 27 gr slug.

That's what I would like to hear about your opinions about the feasibility of the setup before actually dismantling the gun, and add wear and tear to it.

But I'm glad that this topic is of an interest to some of you. Maybe we can find a way to gain high fps without just upping the reg and having heavier hammer,therefore a tamer gun.

Click to expand...

It sounds like you want to cut the dwell, but possible retain the same power?

If so I suggest increasing your regulator, while either running a weaker valve spring AND/OR heavier hammer which should allow you to 'tame' the gun a bit...

You should be able to reduce preload on your hammer spring currently unless its at its minimum to test if you're over-dwelling, your fps would not decrease, in this case you keep reducing preload until your fps does, and then lean back on it a tad to restore.

I know you want to do this without increasing the reg, your next best alternative would be a 700mm barrel...the configuration is violent because of it being pushed to its limit.

-Matt

Using a crown, 110 bar, 27 grain slug, 20 mm distance with 13 wheel position, 700mm barrel, getting 840 fps. Do not know the spring or hammer, whatever came with it stock factory. The bark , recoil is tame and controllable. Using this at 50 yd and 100 yd. Future use at 200 yd is planned, if more energy is needed, I will add more for 200 yd. My plan is to use the least amount of energy as possible, and still get the job done.

bowopt said:

Hi guys,

Thank you so much for the great inputs.

Yes. I'm trying to find the max power I can get with the 22 cal gun with 600 mm barrel (I can't afford another 700mm barrel kit) and the 27gr slug. It's a new gun, so I'm happy tinkering with it. However, in my experience, too much tinkering will introduce a lot wear and tear that will make me cry.

The thing is at 1023 fps with 160 bar, the grouping is quite nice and lowering it to 1000 fps still gives me a nice group, though it's worse than at 1023 fps.

It's just the gun recoils hard and I can hear the twang in the gun much more than I would like to.

Going back to Matt Dubber's tuning high power gun guide. I would like to explore with you guys if, instead of relying on heavier hammer and high reg pressure, we can play with the valve spring with the standar 11 gram hammer weight and spring.

Going back to Matt's reply above. Won't running a heavier hammer with high reg would still make the gun violent? I'm afraid to run the reg any higher than 160 bar because of the possibility of lowering the lifetime of the reg. But I would be glad to hear what the highest pressure the reg can take and still having it at a safe zone?

Thanka so much for sharing and the insights.

Click to expand...

Higher regulator (if possible, I am unsure of the maximum pressure your regulator can take) will take you further away from your plateau if you are operating at it, say you are shooting at 99-100% of your peak but are unhappy with performance at 97% (1000 fps), you can then raise your regulator so your new peak is 1050 fps and de-tuning to 97% will put you at 1023 fps. These are theoretical numbers all based on current performance and how your gun is acting (violent) and assuming your currently operating at 99-100% of your plateau.

Increasing the regulator will require either a weaker valve spring and/or heavier hammer spring/heavier hammer weight to compensate for the increased load holding the poppet shut in the closed state AND closing force acting upon the valve in the open state, you very well may get away with simply adding more pre-load on the hammer spring and making no other changes if there is room for that (ie: not currently maxed out as the current reg setting)

There really is no other alternative to reducing the guns 'violence' without reducing its performance, as you're pushing 62 fpe out of that 600mm barrel, even in the most optimal scenario with half of the barrel volume in air being used prior to the valve shutting, you're spitting out around 30 grains of air on top of the 27 grains of pellet, for a total of 57 grains of mass down the barrel, you're gonna feel that more than a shot that is say, 20% more efficient shooting 59 FPE @ 990 fps which is closer to 23 grains of air on top of the 27 grain of pellet, its just how things work. If you push that same air parcel down a longer barrel, it stretches it out more via longer pressure gradient, (allows for less muzzle pressure). So here you may have say 1000 psi of muzzle pressure with the 600mm barrel, using the same performance but with 700mm barrel puts that muzzle pressure at closer to 750 psi...which would be much less 'violent' feeling.

The load or regulator setting your valve system can take before it feels violent (too high of regulator pressure results in altering a combination of load holding your valve shut in closed state and closing force in open state requiring too much hammer weight/spring combo and therefore overall hammer recoil felt in action) is built into it be design, you'd have to change the balance ratio of the valve (in balanced valves which FX uses) to make the violence of the hammer action much less apparent, which is do-able, but that is another level of tuning and refinement entirely, which I won't dive into here. One could also reduce the closing force acting upon the valve to to reduce hammer strike violence without messing with the balance ratios, but that still takes fairly heavy valve modification.

HTH

-Matt

bowopt said:

Hi guys,

Thank you so much for the great inputs.

Yes. I'm trying to find the max power I can get with the 22 cal gun with 600 mm barrel (I can't afford another 700mm barrel kit) and the 27gr slug. It's a new gun, so I'm happy tinkering with it. However, in my experience, too much tinkering will introduce a lot wear and tear that will make me cry.

The thing is at 1023 fps with 160 bar, the grouping is quite nice and lowering it to 1000 fps still gives me a nice group, though it's worse than at 1023 fps.

It's just the gun recoils hard and I can hear the twang in the gun much more than I would like to.

Going back to Matt Dubber's tuning high power gun guide. I would like to explore with you guys if, instead of relying on heavier hammer and high reg pressure, we can play with the valve spring with the standar 11 gram hammer weight and spring.

Going back to Matt's reply above. Won't running a heavier hammer with high reg would still make the gun violent? I'm afraid to run the reg any higher than 160 bar because of the possibility of lowering the lifetime of the reg. But I would be glad to hear what the highest pressure the reg can take and still having it at a safe zone?

Thanka so much for sharing and the insights.

Click to expand...

Too much YouTube influence will make you cry. Slugs should be optimally stable around 900fps. As Solo says, there’s no need to be pushing into transonic speeds where drift is amplified. Better to go with a larger slug and lower speed to get more power on impact at distance. One hot option right now is to use Altaros CNC slugs, which have a BC of 0.18 and shoot optimally at 885fps. The weight is 32.3grain and you should be able to get that speed from your setup. They are expensive but you can’t beat the quotient of smiles/shot, IMHO. (And the shooting cycle is sedate)

@bowopt the advice above from Matt is excellent. Spend some time digesting it and ask questions if you need help clarifying any of the concepts. Understanding them will help you with adjusting and optimizing most any regulated PCP.

bowopt said:

Hi,

I watch Matt Dubber's YouTube video about tuning for high power airgun.

He mentioned that he uses a weak valve spring in his 22 cal Impact Mk2 with very high reg pressure to achieve 70 fpe with 34 gr slug.

I wonder if we can use that same concept on our guns. In my case, changing the valve spring to a weaker spring, hoping that the valve will close faster on lower rear reg pressure and less hammer for my 22 cal wildcat mk3 bt to shoot 27 gr HP slug at 1000ish fps.

The current settings are 160 bar rear reg pressure and 12 gram hammer which makes the gun quite violent.

I'm hoping to use the 11 gram with weaker preload and lower the rear reg pressure, while having the weak valve spring to close the faster to get higher speed.

What do you guys think? Workable?

Click to expand...

You need to watch that video again .you don't want to lower reg pressure because the high reg pressure and softer spring is what makes the valve close faster..hope this helps.

Just saw this old thread.
How was the results of changing valve springs?

I just purchased 4 different and lighter forced valve springs to test in my FX Crown gen.1

My worries is how much weaker could the valve spring be?
I found 4 standard springs giving from half the force up to a reduction with 15%

I was surprised to calculate that the forces and their relationship on the closed valve generated by air pressure / valve spring.

It seems like the air pressure force at 150 bar is only about 50% of the total closing force, that the hammer needs to strike to open the valve..
So there is power to gain with a lighter spring.

But risk is that when the valve is open at the 150 bar plenum pressure, the 4 mm valve area is blown open, and held open too long time, and will not close before the pressure has dropped considerably.

But I guess the pressure will drop fast when the slug is pushed through the barrel and the plenum pressure drops with the small plenum on a FX Crown.

Looking theoretically the 4 mm valve area generates close to 18 kg stay open force at 150 bar (Theoretically force by a blocked barrel).
The valve will stay open longer time until either the plenum pressure has dropped enough, or at least when the slug left the barrel and pressure is relieved

Next will be the testing more progressive forced springs, meaning reduced spring force at closed position of the valve but 30% more force at the same valve opening distance....

So did any gain some practical experience changing the valve springs

Claus from Denmark

Hehe thats ok.
So I am still on my own figuring out the results.

I will post information on my test after the weekend.

Best regards from Denmark