FX Need general advice on tuning PCP

[TitanRebel]

I'm a multiple hobby kinda guy, and I've tended to cycle through same hobbies over the years. Recently I've re-discovered my love of airguns. About 3 years ago I sold most of my nice German break-barrels to fund my first PCP - FX Maverick compact in .25. Bought it from a dealer that set it up for me, and I was so impressed with the gun I didn't touch it. Well, it hadn't been shot in over a year, until several weeks ago, and now I'm having a blast like it was new again.

I decided I needed to learn how to tune it, so watched a few videos and turned out to be pretty easy. But, I got lots of questions...

Target Velocity - I've seen many people proclaim "pellet XYZ" likes to be shot at 850 - 900 fps... is there some kind of reference I don't know about? How do you know what velocity for which pellet? Or, is this specific to your rifle and pellet choice?

Hammer spring tension vs. regulator pressure - How would do you come up with this "ideal" combination. I found the AEAC tuning video (great video) - so, I followed his regulator pressure suggestions, but not sure how to match that with the correct hammer tension. I assume these things work together and there is some ideal settings for each gun, but how do you "sneak up" on the right settings for each ?

Lastly, it turns out that I've been shooting the Maverick for years, and the second regulator wasn't even being used... is this good/bad idea for wildcat/maverick? The second regulator was set higher than first regulator. It's not anymore after my tune 125/100

thanks for any advice!

 

[MrP]

I'm a multiple hobby kinda guy, and I've tended to cycle through same hobbies over the years. Recently I've re-discovered my love of airguns. About 3 years ago I sold most of my nice German break-barrels to fund my first PCP - FX Maverick compact in .25. Bought it from a dealer that set it up for me, and I was so impressed with the gun I didn't touch it. Well, it hadn't been shot in over a year, until several weeks ago, and now I'm having a blast like it was new again.

I decided I needed to learn how to tune it, so watched a few videos and turned out to be pretty easy. But, I got lots of questions...

Target Velocity - I've seen many people proclaim "pellet XYZ" likes to be shot at 850 - 900 fps... is there some kind of reference I don't know about? How do you know what velocity for which pellet? Or, is this specific to your rifle and pellet choice?

Hammer spring tension vs. regulator pressure - How would do you come up with this "ideal" combination. I found the AEAC tuning video (great video) - so, I followed his regulator pressure suggestions, but not sure how to match that with the correct hammer tension. I assume these things work together and there is some ideal settings for each gun, but how do you "sneak up" on the right settings for each ?

Lastly, it turns out that I've been shooting the Maverick for years, and the second regulator wasn't even being used... is this good/bad idea for wildcat/maverick? The second regulator was set higher than first regulator. It's not anymore after my tune 125/100

thanks for any advice!

It is interesting figuring these things out I wish you luck, and will leave most of it to those here who may have more experience.

As far as the hammer spring and the pressure of air you're trying to release goes, if you are shooting at higher pressure it is going to take a stronger hit with the hammer to open the valve, as the pressure in the tank exerts closing force on the valve. So as you increase the pressure in your regulator, you typically need to increase the amount of spring load on your hammer and vice versa. If you don't have enough spring load only a little bit of air will get out.

 

[Chukar60]

Way I tune my Maverick Compact (owned it three years, tuned it three times) is to set the PW on 6 or 7, then back the hammer screw out until the gun will not cock. Start turning the hammer screw in 1/4 turn increments until it will cock. At that point I will screw it in another half turn.
Starting at about 90 bar on the second reg, increase the reg pressure in 5 bar increments until you are about 90 fps over your target velocity. My gun really likes the FX 25.4 gr pellets and shoots them best at around 885 fps. So, I want my high velocity setting to be close to 970 fps. Once there, start screwing the IHS in half a turn at a time. Shoot 10 shots to settle the springs in, then 3 shots to get an average speed. At this point I am not worried about standard deviations of velocity. Repeat this process until you have reduced velocities very near your target velocity.
Once there you can fine tun the IHS for small standard deviations and final accuracy.
Bear in mind that with a short barreled gun you want a short burst of air. Short enough that you are not having excess air washing the back of your projectile when it leaves the barrel.
Which projectile at what speed? That is where you get a healthy amount of trigger time. You will just have to play with different projectiles and see what speed they shoot the best at from your gun.

 

[Emu]

My humble and good faith advice: just play "a little" with the hammer spring and feel the rifle.

Do not mess with the regulator if you want to keep your mind on your day a day occupation as usual.

 

[TitanRebel]

Way I tune my Maverick Compact (owned it three years, tuned it three times) is to set the PW on 6 or 7, then back the hammer screw out until the gun will not cock. Start turning the hammer screw in 1/4 turn increments until it will cock. At that point I will screw it in another half turn.
Starting at about 90 bar on the second reg, increase the reg pressure in 5 bar increments until you are about 90 fps over your target velocity. My gun really likes the FX 25.4 gr pellets and shoots them best at around 885 fps. So, I want my high velocity setting to be close to 970 fps. Once there, start screwing the IHS in half a turn at a time. Shoot 10 shots to settle the springs in, then 3 shots to get an average speed. At this point I am not worried about standard deviations of velocity. Repeat this process until you have reduced velocities very near your target velocity.
Once there you can fine tun the IHS for small standard deviations and final accuracy.
Bear in mind that with a short barreled gun you want a short burst of air. Short enough that you are not having excess air washing the back of your projectile when it leaves the barrel.
Which projectile at what speed? That is where you get a healthy amount of trigger time. You will just have to play with different projectiles and see what speed they shoot the best at from your gun.

Thanks! The process to get there is what I was looking for...

So, you start by maxing the hammer spring; then try to get 90fps higher than your target velocity - I assume this is because you want power wheel setting #7 to be that +90 velocity? Then you get your "target velocity" by turning the power wheel down to 6,5,4,3 etc..?

It could be I'm misunderstanding how the "adjustment" setting on the power wheel works... I assume when you adjust via the 1.5mm hole, you are setting the hammer spring tension for wheel setting #7 - all the other settings simply decrease hammer spring from that top setting... is that right?

 

[elh0102]

I can't address the specific adjustments in your rifle, but I know FX usually has a bunch. But generally, a well balanced tune will be achieved when the rifle is shooting around 95% of the maximum velocity attainable with the existing reg and HST settings. So, if you're fine tuning, you may be able to use the HST adjustment only. If you are getting significantly out of the general relationship mentioned, then you should probably move the reg set point also.

 

[TitanRebel]

I can't address the specific adjustments in your rifle, but I know FX usually has a bunch. But generally, a well balanced tune will be achieved when the rifle is shooting around 95% of the maximum velocity attainable with the existing reg and HST settings. So, if you're fine tuning, you may be able to use the HST adjustment only. If you are getting significantly out of the general relationship mentioned, then you should probably move the reg set point also.

So, if I'm understanding correctly... you're suggesting with regulator set at XXX bar, increase HST until velocity isn't going up anymore (max velocity), then back HST down until 95% of that max velocity is achieved? Sounds reasonable, thanks!

 

[JimD]

You can always try different velocity but others report instability, most noticable at 100 yard than at 30 yards, at velocities somewhere over 900 fps. Some JSB pellets, newer 22s and 25s are reportedly stable and accurate up to something south of 950 fps. Some of my guns will not go much over 800 fps with the pellets they prefer. My Prod will only do about 750 fps with the copper plated H&N FTT pellets it prefers. I tune for 800-900 when the gun will do it, typically, but my Caiman seems happiest at about 915 with the H&N Baracuda 18 it likes. I have not tried reducing the regulator pressure.

So my normal process is to see if I can get in the 800-900 fps velocity range with a pellet the gun likes. I have never found a gun to like a pellet at one velocity and not like it at another. I am not trying to say they are all equally accurate, just that it doesn't seem to matter exactly how the gun is tuned when you screen pellets. I want a regulator setting that will give me a maximum velocity over 900 fps if possible with maximum hammer spring force for that regulator setting. I go up 1/4 or 1/2 turn a time on the hammer spring to find what the maximum is (or I go down if increasing the hammer spring does not increase velocity). The normal suggestion is to set the hammer spring to a velocity about 5% below that peak. I try that but I also test accuracy as I reduce the hammer spring. If I find it to be more accurate to stop at 3% below that is what I do. Another thing I check, particularly when I am set at 5% below, is the velocity of the first shot after the gun has set overnight. Sometimes it will be low. I like to pest with my airguns and I do not want the first shot to be low for that so if it is I turn it up a little and try again.

If I cannot get at least 800 fps at the 5% below level, I increase the regulator pressure. If I am way over 900 fps I reduce it. My Caiman X arrived with a regulator at 100 bar. If is most accurate with 18 grain pellets and the peak with that pellet is about 940 fps. When I reduced it to 880 or so with the hammer spring I was much under 5% below which may be why it is a little more accurate at over 900 fps. It might be even more accurate if I dropped the regulator pressure and retuned for 880 but I am pretty happy with it, at least for now, where it is. Changing the regulator on this gun is also pretty involved (you have to pretty completely disassemble the gun, I've done it but it is not just degassing and turning a screw).

 

[elh0102]

So, if I'm understanding correctly... you're suggesting with regulator set at XXX bar, increase HST until velocity isn't going up anymore (max velocity), then back HST down until 95% of that max velocity is achieved? Sounds reasonable, thanks!

Well, yes, but if that velocity isn't what you want, then you may need to change your reg set point and start over. A good balance doesn't necessarily mean the best tune. It gets down to the tuning balance that delivers the velocity you want. I would say, forget about the tuning balance until you have found the target velocity, then get it right.

 

[Chukar60]

Thanks! The process to get there is what I was looking for...

So, you start by maxing the hammer spring; then try to get 90fps higher than your target velocity - I assume this is because you want power wheel setting #7 to be that +90 velocity? Then you get your "target velocity" by turning the power wheel down to 6,5,4,3 etc..?

It could be I'm misunderstanding how the "adjustment" setting on the power wheel works... I assume when you adjust via the 1.5mm hole, you are setting the hammer spring tension for wheel setting #7 - all the other settings simply decrease hammer spring from that top setting... is that right?

If you follow the process you are looking for max hammer spring. So start at 6 or 7 then back the IHS out until the gun wont cock. You are now at max safe hammer spring.
Once you have the tune set that you like you can adjust the PW down if you want to shoot low power. The tune at lower settings probably wont be perfect but close enough for a short session or need for lower power.
The velocity over your target is subjective. Some people will say 6-7%. I go to 10% and work down. The point of this method is to produce a high pressure, short burst of air in order to eliminate projectile wash from excess air.

 

[jakob8572]

I found this very helpful in understanding how the Hammer Spring and Tension work. I’m not a fan of this method and ended up going with the micrometer that’s also shown in the video (easier for me to see numbers than taking a guess at what my distance is).

For some starting points, you can also check the DOPE table for the Maverick - here. I think as long as your pellets / slugs are flying straight, you can play around velocity has some wiggle room. I’ve got a FX Maverick Sniper (.25) and am currently shooting JSB Hades ~880 - 890 FPS - Front Reg set at 120 and 80-90 in the Rear (last session was ~180 shots on one fill). I tried a couple of other tunes I found online and some worked, some didn’t (it’s true that every gun is different). All I can say is it’s about finding a balance between whatever your Reg Pressure is and your Hammer Spring Tension.

 

[Trucker3573]

What pellet are you using ?

 

[TitanRebel]

What pellet are you using ?

FX 25.39 - which I think is exact same pellet as JSB Exact King 25.39

 

[Trucker3573]

FX 25.39 - which I think is exact same pellet as JSB Exact King 25.39

You are spot on with 100 bar on the reg. Should sweet spot them right around 900. I tune opposite as some. I choose the reg pressure then on the Maverick turn the internal HS screw clockwise almost all the way in. Start at a very low spring tension and gradually work it up until the velocity peaks and doesn’t go up anymore. At that spot you have a great balance between HS and reg pressure. It’s easy to over shoot that spot a little so once you get close you can tweak it in very small increments to find it perfectly. I always did my tune on power wheel 7 so then you can dial down if you want to. My experience with the maverick and wildcat BT is they don’t perform all that consistently off that sweet spot. You might get one maybe 2 drops on the big power wheel. After that the extreme velocity spread goes all to hell. 100 bar should put you right around 900 on a really good tune with 25.39