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FX FX Panthera Tuning Methodology

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johninoregon

Member
Aug 31, 2023
23
13
Pleasant Hill, Oregon USA
My question has to do with the actual procedure and protocol you use to set up your FX Panthera for different slugs and pellets. When I speak of methodology, I am speaking to the process to figure out the regulator and HST settings for a slug or pellet of a certain grain weight.

The manual that comes with my FX Panthera 25 caliber 600 mm barrel air rifle has ideas that help one start. For example, it says to start with the macro hammer spring tension adjuster set to 13. Then using the micro HST adjuster to fine tune the hammer spring tension. It does not tell you specifically when to do this, but it does tell you how to do this. I want to know the when do I do this operation?

The next thing in the manual is the externally adjusted AMP regulator. It tells you where the hex screw is located and to turn it counterclockwise to increase regulator pressure, and clockwise to decrease pressure. The manual also provides you with the warnings about making sure that the plenum is depressurized prior to making these adjustments. It tells you to fire the air gun several times after making approximately one-fourth turn adjustment. Then observe the regulator pressure to see if it is stabilized at its new setting. Again, when, and why should someone perform this regulator change is a mystery.

Nowhere does the manual ever establish the protocol to use when tuning the air gun for a pellet or slug. That is what I am trying to get to. Here are my questions and I would appreciate detailed answers.

1. What is the protocol to follow to achieve a good tune, and how will I know when I am at the good tune point? What I am looking for is a detailed step by step process that one could use to achieve a good tune for a specific slug or pellet out of the FX Panthera 600 mm. The reason I say 600 mm is because it does have the heavy superior barrel for slugs.

2. Often, I see statements like "I'm trying to achieve 935 ft per second with a 40-grain slug". My question is how does one know what FPS is good for a specific slug or pellet? Where do these numbers come from?

3. When my FX Panthera arrived, it was set up NICELY for JSB match Diablo King heavy Pellets 33.95 grain. My regulator was at 110 bar and HST set to 2.3. The pellets travel at 875 ft per second on average. At 50 yards it is dead accurate. Now I would like to know what other FX Panthera 25 caliber 600 mm barrel owners have determined for their air gun regarding other slugs and pellets. For example, I would love to have FX Panthera settings (regulator and HST) in terms of FPS for JSB knockout slugs 33.49 grain, FX hybrid slugs 26 grain, Zan 41 grain slugs and AVS 40 grain slugs .2503 diameter. Of course, all these projectiles are for a 25 caliber FX Panthera.

The essence of what I am looking for is the methodology of achieving a good tune for an FX Panthera. Step by step what do you do to achieve a good tune? Where do you start? How do you know when you have achieved a good tune? How do you determine what is a good FPS for a specific slug or pellet? How do I know when I am wasting air?

Please share your ideas and methods with the FX Panthera community.
 
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Oregon John,

To simplify all this tuning “stuff” that you hear on these forums…

… let’s take tuning in 2 parts:

#1: What is the optimal velocity for accuracy for a given projectile – that is determined by trial & error (target shooting / group shooting) [This is the answer to your Question #2]

#2: What is the best way to set up my rifle for that optimal velocity – this is discussed in the HAM article and below. [This I discuss below and is the answer to your Questions #1 & 3]

These two things are interrelated, but different.

Let me give you an example:
I recently set up my FX PowerPup to shoot FX 18.13g pellets…

Tune #1: Reg at 100bar, adjusted HS to shoot at 895fps. Accuracy was very good. Shot count was 65 before falling off regulator

Tune #2: Reg at 135bar, adjusted HS to shoot at 895fps. Accuracy was very good. Shoot count was 118 before falling off the regulator.

Tune #1: is on the “plateau” from the Hard Air Magazine article. It works but lots of wasted air.

Tune #2: more than 10% below vs the knee from the article. It works and is super efficient, but shot string is slightly jagged and velocity actually goes up when falling off the regulator.

So, since I’ve previously determined (via target shooting / shooting groups) that 895fps was a very accurate velocity with 18.13g pellets with this particular rifle, now I want to “tune in” for maximum efficiency at this velocity.

As can be seen above, my “best tune” for the 18.13g with the PowerPup is likely with the regulator set around 120-125 bar. As per the article, I want to find a regulator setting where my velocity peaks at 933fps. Then I will reduce HS preload tension to lower velocity to 895fps – 895 is 96% of 933 – this is referred to as the 96% tune – a tune where most PCPs achieve an excellent balance between efficiency and power.

Every projectile will be different.

Let’s take your example. Your Panthera is shooting 33.95g pellets very accurately at 875fps. You have your regulator set at 110bar.

What is the maximum velocity that you can achieve with these pellets (reg staying at 110bar) if you max out your hammer spring preload? Is there a point where velocity stops increasing as you add preload – this is your velocity plateau, and you can apply the info in the HAM article to determine where your “tune” falls on the “knee”.

I’m not so sure that you will be able to shortcut this and develop a “cheat sheet” of optimal settings for specific projectiles (reg and hammer spring preload) by gathering input from other FX Panthera .25 cal 600mm barrel users. Every barrel is different. Gathering the info may get you somewhat close, but I still believe that you will have to:

#1: Find the optimal velocity for your rifle with that projectile

#2: Tune the regulator and hammer spring preload to the “96% of max velocity tune” for that particular projectile

I hope this helps simplify all the buzz around “tuning” ,

-Ed
 
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EPG said:
Oregon John,

To simplify all this tuning “stuff” that you hear on these forums…

… let’s take tuning in 2 parts:

#1: What is the optimal velocity for accuracy for a given projectile – that is determined by trial & error (target shooting / group shooting) [This is the answer to your Question #2]

#2: What is the best way to set up my rifle for that optimal velocity – this is discussed in the HAM article and below. [This I discuss below and is the answer to your Questions #1 & 3]

These two things are interrelated, but different.

Let me give you an example:
I recently set up my FX PowerPup to shoot FX 18.13g pellets…

Tune #1: Reg at 100bar, adjusted HS to shoot at 895fps. Accuracy was very good. Shot count was 65 before falling off regulator

Tune #2: Reg at 135bar, adjusted HS to shoot at 895fps. Accuracy was very good. Shoot count was 118 before falling off the regulator.

Tune #1: is on the “plateau” from the Hard Air Magazine article. It works but lots of wasted air.

Tune #2: more than 10% below vs the knee from the article. It works and is super efficient, but shot string is slightly jagged and velocity actually goes up when falling off the regulator.

So, since I’ve previously determined (via target shooting / shooting groups) that 895fps was a very accurate velocity with 18.13g pellets with this particular rifle, now I want to “tune in” for maximum efficiency at this velocity.

As can be seen above, my “best tune” for the 18.13g with the PowerPup is likely with the regulator set around 120-125 bar. As per the article, I want to find a regulator setting where my velocity peaks at 933fps. Then I will reduce HS preload tension to lower velocity to 895fps – 895 is 96% of 933 – this is referred to as the 96% tune – a tune where most PCPs achieve an excellent balance between efficiency and power.

Every projectile will be different.

Let’s take your example. Your Panthera is shooting 33.95g pellets very accurately at 875fps. You have your regulator set at 110bar.

What is the maximum velocity that you can achieve with these pellets (reg staying at 110bar) if you max out your hammer spring preload? Is there a point where velocity stops increasing as you add preload – this is your velocity plateau, and you can apply the info in the HAM article to determine where your “tune” falls on the “knee”.

I’m not so sure that you will be able to shortcut this and develop a “cheat sheet” of optimal settings for specific projectiles (reg and hammer spring preload) by gathering input from other FX Panthera .25 cal 600mm barrel users. Every barrel is different. Gathering the info may get you somewhat close, but I still believe that you will have to:

#1: Find the optimal velocity for your rifle with that projectile

#2: Tune the regulator and hammer spring preload to the “96% of max velocity tune” for that particular projectile

I hope this helps simplify all the buzz around “tuning” ,

-Ed
Click to expand...
Ed thank you for your information. Exactly the kind of information I'm looking for. This is the first PCP airgun owned by me that could be tuned with external controls. My other air gun is an American Air Arms EVOL 30 caliber. The EVOL does not provide external controls for tuning.

I have not yet read the article but I will shortly. There is one additional question that you might be able to help with. Do you pick one specific projectile for your gun and stick with it or do you have several favorites, maybe one a slug and one a pellet. I'm assuming you zero your scope for each one. The scope zero and the projectile need to match for accuracy. How do you handle this situation?

John
 
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darknes said:
I read what is written here. I can't understand why someone is solving macro settings. those who write it and solve it should unscrew it and hide it somewhere and find out that the whole setting is dependent on the micro. the entire function of the macro wheel is only to move the micro in steps.
Click to expand...
I think the FX user manual could have done a better job explaining it. If you look at the FX manual they have a section that you can record your settings. They have a spot for Macro Adjuster setting and Micro adjuster setting. This would lead one to believe that they are independent of each other. I think they should have called the scale for the micro adjuster simply the hammer strength gauge. The knob the hammer strength macro adjuster and the barrel roller the hammer strength micro adjuster and then make it clear that the true measure was only what is reflected on the hammer strength gauge. ie there is no deference between "5 Macro 2 micro" and "13 Macro 2 Micro". They are both 2 on the hammer strength gauge.
 
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johninoregon said:
Ed thank you for your information. Exactly the kind of information I'm looking for. This is the first PCP airgun owned by me that could be tuned with external controls. My other air gun is an American Air Arms EVOL 30 caliber. The EVOL does not provide external controls for tuning.

I have not yet read the article but I will shortly. There is one additional question that you might be able to help with. Do you pick one specific projectile for your gun and stick with it or do you have several favorites, maybe one a slug and one a pellet. I'm assuming you zero your scope for each one. The scope zero and the projectile need to match for accuracy. How do you handle this situation?

John
Click to expand...

Hi John,

Good question – I’ll share the conclusions I’ve come to…

I’m primarily a target shooter. 99% of the time. The other shooting is just pest control.

Maximum accuracy – precision target shooting accuracy – is obtained with pellets.

You are shooting an FX rifle, they were designed around JSB/FX/AA diabolo pellets (their pellet liners were).

There are about two pellets in each caliber that its worth tuning for (IMHO):

.177 – 10.3g and 13.4g (another is the H&N FT 9.57g – hard to find)
.22 – 15.89g and 18.13g
.25 – 25.4g and 33.95g
.30 – 44g and 50g (and possibly the Zan 56g)

Within a caliber, if I develop a good tune for one of the two pellet weights, I should be able to get a reasonable tune for the other pellet without having to adjust regulator pressure. Simply by adjusting hammer spring preload.

Quick story: I have a FX Crown .22 that was shooting lights out with 15.89g (awesome efficiency as well) with 380mm barrel. I popped on a 500mm barrel and adjusted NOTHING. The 500mm shot the 18.13s at the exact same speed as the 380mm shot the 15.89s – and accuracy has been lights out. I’m talking precision target scores of 195+ at 40 Yard Challenge (10-ring is .125” – center X is .04”). [Group shooting is for guys that can’t target shoot, lol]. So, one tune for two pellet weights – and I simply swap BARRELS. That was a bit lucky, and unexpected.

I’m not hunting, so I don’t shoot slugs often. I’ve done some minor experimenting, but nothing more.

The bottom line is that pellets are drag stabilized projectiles and slugs are spin stabilized projectiles. If you are using the same barrel to shoot both, it will be a significant compromise – as spin stabilized projectiles will typically require barrels with faster twist rates (more spin). The contact area of slugs in the bore is much higher than the contact area of a pellet – so friction increases.

Basically, you are adding so many variables when you try to tune one rifle for two different TYPES of projectiles. Much more involved than tuning for two different weights of ONE type of projectile, IMHO.

I’d recommend setting up your rifle for either your preferred pellet or preferred slug. Let’s say it’s the 33.89g pellet. Then if you find a slug that also works with that tune – great. If you can’t find a slug that works with the 33.89g pellet tune – then get a second dedicated slug rifle.

The reason for this recommendation is that I’m always a bit hesitant to keep adjusting regulator pressure. These regulators are just stacks of bellville washers. I think it always takes a bit of time for them to “settle down” once you change the reg pressure. So, if you are looking for precision, it seems to me that you want to avoid constantly changing regulator pressures up & down to accommodate different projectiles and projectile weights.

Just my thoughts and experience to date,

Ed
 
Upvote 1
EPG said:
Hi John,

Good question – I’ll share the conclusions I’ve come to…

I’m primarily a target shooter. 99% of the time. The other shooting is just pest control.

Maximum accuracy – precision target shooting accuracy – is obtained with pellets.

You are shooting an FX rifle, they were designed around JSB/FX/AA diabolo pellets (their pellet liners were).

There are about two pellets in each caliber that its worth tuning for (IMHO):

.177 – 10.3g and 13.4g (another is the H&N FT 9.57g – hard to find)
.22 – 15.89g and 18.13g
.25 – 25.4g and 33.95g
.30 – 44g and 50g (and possibly the Zan 56g)

Within a caliber, if I develop a good tune for one of the two pellet weights, I should be able to get a reasonable tune for the other pellet without having to adjust regulator pressure. Simply by adjusting hammer spring preload.

Quick story: I have a FX Crown .22 that was shooting lights out with 15.89g (awesome efficiency as well) with 380mm barrel. I popped on a 500mm barrel and adjusted NOTHING. The 500mm shot the 18.13s at the exact same speed as the 380mm shot the 15.89s – and accuracy has been lights out. I’m talking precision target scores of 195+ at 40 Yard Challenge (10-ring is .125” – center X is .04”). [Group shooting is for guys that can’t target shoot, lol]. So, one tune for two pellet weights – and I simply swap BARRELS. That was a bit lucky, and unexpected.

I’m not hunting, so I don’t shoot slugs often. I’ve done some minor experimenting, but nothing more.

The bottom line is that pellets are drag stabilized projectiles and slugs are spin stabilized projectiles. If you are using the same barrel to shoot both, it will be a significant compromise – as spin stabilized projectiles will typically require barrels with faster twist rates (more spin). The contact area of slugs in the bore is much higher than the contact area of a pellet – so friction increases.

Basically, you are adding so many variables when you try to tune one rifle for two different TYPES of projectiles. Much more involved than tuning for two different weights of ONE type of projectile, IMHO.

I’d recommend setting up your rifle for either your preferred pellet or preferred slug. Let’s say it’s the 33.89g pellet. Then if you find a slug that also works with that tune – great. If you can’t find a slug that works with the 33.89g pellet tune – then get a second dedicated slug rifle.

The reason for this recommendation is that I’m always a bit hesitant to keep adjusting regulator pressure. These regulators are just stacks of bellville washers. I think it always takes a bit of time for them to “settle down” once you change the reg pressure. So, if you are looking for precision, it seems to me that you want to avoid constantly changing regulator pressures up & down to accommodate different projectiles and projectile weights.

Just my thoughts and experience to date,

Ed
Click to expand...
Ed what you say makes perfect sense to me. My FX Panthera came with the heavy superior slug barrel. But I'm not locked into shooting slugs. I just want something that would be accurate at 100 yd. Even if I had to purchase the 600 mm standard pellet barrel I would do so. I'm assuming I just change out the liner. I believe it has a different twist rate than my slug barrel.

I found a YouTube video that explains PCP tuning and it matches exactly what you said. Here's the link:


I hope airgun Nation doesn't mind me posting a link. Ed thank you so much for your intelligent response. My background is technical so I was looking for some of the technical reasons and methods and you provided that. I read the article and I'll probably need to read it a few times to absorb. Excellent information.

John
 
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My .25 Panthera 600 shooting 49.5 Altaros ATP Smooth at 888 fps.
Reg pressure approx 135 bar. Micro at just a hair over 3.5. I get 22 shots on reg from 250 bar fill.
Setup below is not how I usually shoot it but wanted to check accuracy with Benchrest setup.
Shot string is one full 15 shot mag. ES of 1 fps and SD under 1/2 fps. Super consistent. Note that BC is G7 profile, not G1 or RA4.

IMG_1842.jpeg


IMG_1843.jpeg
 
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johninoregon said:
That is amazing consistency. Thank you for the setup information. I will try the Altaros slugs. Do you have the standard hammer in the gun?
Click to expand...
Thanks. Yes, the gun is stock. I shot another 15 shot mag after refill to 250 bar and the ES was 1 fps, SD under 1/2 fps. So that’s 30 consecutive shots where each one was 888 or 889 fps.
 
Last edited:
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bdzjlz said:
My .25 king with the 600 barrel has the macro adjuster set at 23 and the micro at about 31/2 and the reg set just under 150. Is shooting the Alteros 50 Gr and H&N 46 Gr heavy slugs “lights out.”
Click to expand...
Thank you for sharing this.... What speed does this send generate for the Alteros and H&N's. I have the .25 Dynamic Express and am trying to to drive 36 grain Javelins around 980 but am not getting the accuracy I was hoping for.
 
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darknes said:
I read what is written here. I can't understand why someone is solving macro settings. those who write it and solve it should unscrew it and hide it somewhere and find out that the whole setting is dependent on the micro. the entire function of the macro wheel is only to move the micro in steps.
Click to expand...
One of the first things I notice every time I see it too.
 
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Centercut said:
My .25 Panthera 600 shooting 49.5 Altaros ATP Smooth at 888 fps.
Reg pressure approx 135 bar. Micro at just a hair over 3.5. I get 22 shots on reg from 250 bar fill.
Setup below is not how I usually shoot it but wanted to check accuracy with Benchrest setup.
Shot string is one full 15 shot mag. ES of 1 fps and SD under 1/2 fps. Super consistent. Note that BC is G7 profile, not G1 or RA4.

View attachment 424968

View attachment 424970
Click to expand...
Was .138 the last shot BC? If so, that's a pretty big spread from the average. Any idea what's going on there? How far out were you shooting?
 
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ikaros said:
Was .138 the last shot BC? If so, that's a pretty big spread from the average. Any idea what's going on there? How far out were you shooting?
Click to expand...
BC varies by shot and what the radar picks up. That’s why you do at least ten shots so you get an average. You can see there was no variance since the ES is 1 fps. I was shooting at 100 yards.
 
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Centercut said:
BC varies by shot and what the radar picks up. That’s why you do at least ten shots so you get an average. You can see there was no variance since the ES is 1 fps. I was shooting at 100 yards.
Click to expand...
I ask because ive been doing a lot of shooting out to 260ys recently where BC std dev and ES matter a lot. I can get super consistent speeds but if my BC spreads are poop it is super obvious down range. Shooting patriot javelins with my dynamic produced these results and switching to zans was a huge improvement.
 
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