FX Critique my tune

[Plinkalot]

I’m new to PCP’s, have looked at several tuning videos and have experimented with the various adjustments to see what they do.

I think I have a good setup for my gun and this pellet, but have no idea if that’s true. So I’d appreciate a critique, especially from other Impact M4 shooters.

I tried to tune first for FPS, then accuracy, then air usage. When my sights behave I get very good groups at 50ft.


Gun: FX Impact M4 Sniper .22 cal – standard 700mm barrel
- FYI: I’ve fired over 1500 rounds, all JSB, so the gun should be normalized.

Pellet: JSB Exact Jumbo, 15.89gr

Regulator: 93 bar

Macro: 8

Micro: 3.0

Valve: 4 + 1 notch

FPS: Average for 27 rounds: 933, high 946, low 924

Air usage: 0.67 bar/round


How did I do?

Thanks for the help

 

[Chukar60]

I have two M3’s and tuning is the same.
What are you describing as very good groups? Five shots in a slightly enlarged pellet hole? All the holes slightly overlapping?
Your extreme spread is too high and we don’t know what your standard deviation is.
My experience is when you see high ES (extreme spread) and high SD (standard deviation) too much hammer is being applied to the valve.
Unless you are wanting to move up and down the Macro wheel settings for different weight projectiles you can ignore it. Concentrate on the Micro.
With what you are showing I am guessing your valve is staying open too long. A result of too much hammer or not enough plenum pressure.
Start by backing the Micro wheel down a few clicks fire 12 shots and see what the velocity does. You are looking for a slight, consistent drop in velocity. Then go to your valve knob and working in 1/4 turn adjustments in, go until you see another consistent drop in velocity. Make sure you shoot at least 10 shots before trusting what you are seeing on your chronograph. Takes some cycles to get everything settled in.
you should see the ES shrink and the SD shrink as well. You can fine tune from there.
When I tune I am looking for an ES of no more than 8-10 fps and a SD of around 5 fps. Sometimes you can get them smaller, sometimes you cannot.
Best of luck to you. Hopefully some others will chime in with their advice and help.

 

[Plinkalot]

I have two M3’s and tuning is the same.
What are you describing as very good groups? Five shots in a slightly enlarged pellet hole? All the holes slightly overlapping?
Your extreme spread is too high and we don’t know what your standard deviation is.
My experience is when you see high ES (extreme spread) and high SD (standard deviation) too much hammer is being applied to the valve.
Unless you are wanting to move up and down the Macro wheel settings for different weight projectiles you can ignore it. Concentrate on the Micro.
With what you are showing I am guessing your valve is staying open too long. A result of too much hammer or not enough plenum pressure.
Start by backing the Micro wheel down a few clicks fire 12 shots and see what the velocity does. You are looking for a slight, consistent drop in velocity. Then go to your valve knob and working in 1/4 turn adjustments in, go until you see another consistent drop in velocity. Make sure you shoot at least 10 shots before trusting what you are seeing on your chronograph. Takes some cycles to get everything settled in.
you should see the ES shrink and the SD shrink as well. You can fine tune from there.
When I tune I am looking for an ES of no more than 8-10 fps and a SD of around 5 fps. Sometimes you can get them smaller, sometimes you cannot.
Best of luck to you. Hopefully some others will chime in with their advice and help.

Thanks for that... it will take a bit to digest it all but your response is what I'm looking for.

Yes, "Good groups" means I was grouping 3 shots that overlapped. I like to shoot 3 shot patterns as the target gets pretty fuzzy after three tight shots and it gets hard to tell where the 4th and 5th shots land... just me.

You mentioned spread and my gun always has a large spread compared to the tuning videos I watch. What I've found is opening up the valve is the easiest way to increase FPS. I had the valve on 4 + no flats and was averaging 905FPS with a high of 919 and low of 895 on the set I shot just before the results I posted.

What I really need to understand is what the valve and micro wheel actually do. Supposedly the micro adjusts the start of air flow and the valve controls the shut off of air. I'd like to understand how these things work mechanically, not just the results of moving them.

As I see it, the macro wheel and it's setting doesn't really matter because all it does is move the micro wheel, i.e., the macro can be on 1 or 16 but if the micro is on 3 for both those settings, the effect is identical. So it seems the macro should be on "8" all the time so you have max adjustibility for the micro. Does that make sense?

Concerning air consumption, I was taking my tank's pressure before and after a certain number of rounds and dividing the difference by the number of rounds. Do you ever look at your air consumption that way?

My M4 .22 says it can get "up to 330 shots". I imagine that's under ideal conditions and with very light pellets. With my air consumption, going from 250-100 bar I could get 225 rounds which seems like that would be in the ballpark per the spec but with a heavier pellet. So I'm wondering if I am using "too much air"?

Thanks again

 

[Trucker3573]

The valve adjuster at the end should not be used to regulate FPS other than slightly cutting it at the end of the tune. That is only used in the end of your tuning process to maximize efficiency. I don’t have any experience with 22 in the impact but a couple of observations. One being 3 on the micro seems excessive with a 93 bar reg. The second is just a general observation. A 700mm 22 is going to be a bit of a task (I would think at least) to get a good consistent tune with a 15.89 pellet. That is a very light pellet and the impact especially in 700mm is a very powerful gun. Might not get a super low ES. It’s going to be like idling an engine at the brink of stalling. Probably won’t run efficiently. I would get some 25.39 pellets and retune for those. 15.89 would be ok in a compact but really light for the 700mm sniper.

 

[Plinkalot]

The valve adjuster at the end should not be used to regulate FPS other than slightly cutting it at the end of the tune. That is only used in the end of your tuning process to maximize efficiency. I don’t have any experience with 22 in the impact but a couple of observations. One being 3 on the micro seems excessive with a 93 bar reg. The second is just a general observation. A 700mm 22 is going to be a bit of a task (I would think at least) to get a good consistent tune with a 15.89 pellet. That is a very light pellet and the impact especially in 700mm is a very powerful gun. Might not get a super low ES. It’s going to be like idling an engine at the brink of stalling. Probably won’t run efficiently. I would get some 25.39 pellets and retune for those. 15.89 would be ok in a compact but really light for the 700mm sniper.

Thanks for that.

I watched a well regarded tuning video where the fellow says to start out at 6 on the valve. So I'm confused about the valve, micro and regulator and what they physically do? Any help with the mechanics of those would be appreciated.

Since I'm new to all this, you mentioned 3 micro and 93 reg as excessive... in what sense? Excessive meaning 3 is too high or 93 is too high? What will changing them do?

I'm using the 15.89 pellets for plinking as heavier pellets=more lead=more $. I've tried both the JSB Monster's at 25.39gr and Beast's at 33.956gr and have rudimentary tunes for each. I have 4 tins of the 25.39 coming from Pyramid. Once I get them and get a tune going I'll probably post again for a critique of that pellet and tune.

Thanks again.

 

[Plinkalot]

A lot of my confusion about tuning is that I don't understand the adjusters and what they do. (I'm an engineer if ya gotta know.) So let me try it this way.

What does changing the regulator do?

What does changing the micro do?

What does changing the valve do?

Thanks again.

 

[elh0102]

Ultimately, all that matters is accuracy. The only way I know to tune is to first determine my velocity goal. Once that is a given, then work on balance. Frankly, I don't think that you can make that determination based on a 50 foot target. Any reasonable velocity should shoot one-hole groups at 50 feet.
I suggest starting the process at around 30 yards. Start with a relatively high reg set point (you will adjust it later). Then just adjust the HST and try a range of velocities, maybe from 820 to 920 fps. If the best performance is indicated at 890, then that's your goal, and begin working on balance to yield it. Generally, something around 95% of the maximum velocity at a given reg set point will work well. So, in that scenario, you might want reg and HST settings that max out around 930 fps, then back off the HST a bit.

 

[nobody1]

I’m new to PCP’s, have looked at several tuning videos and have experimented with the various adjustments to see what they do.

I think I have a good setup for my gun and this pellet, but have no idea if that’s true. So I’d appreciate a critique, especially from other Impact M4 shooters.

I tried to tune first for FPS, then accuracy, then air usage. When my sights behave I get very good groups at 50ft.


Gun: FX Impact M4 Sniper .22 cal – standard 700mm barrel
- FYI: I’ve fired over 1500 rounds, all JSB, so the gun should be normalized.

Pellet: JSB Exact Jumbo, 15.89gr

Regulator: 93 bar

Macro: 8

Micro: 3.0

Valve: 4 + 1 notch

FPS: Average for 27 rounds: 933, high 946, low 924

Air usage: 0.67 bar/round


How did I do?

Thanks for the help

A 22 FPS spread is fine, if you paid less than $300-$400 for your PCP.
For a $2000+ PCP I would expect better.

I can get a 20 FPS spread from most of my $300-$400 PCPs after I tune them.

 

[nobody1]

Expensive air guns seem to need expensive pellets
After all if you spent $2000 for an air gun, what is $25 for 500 ,22 JSB (flavor of the day) pellets.

 

[Trucker3573]

Thanks for that.

I watched a well regarded tuning video where the fellow says to start out at 6 on the valve. So I'm confused about the valve, micro and regulator and what they physically do? Any help with the mechanics of those would be appreciated.

Since I'm new to all this, you mentioned 3 micro and 93 reg as excessive... in what sense? Excessive meaning 3 is too high or 93 is too high? What will changing them do?

I'm using the 15.89 pellets for plinking as heavier pellets=more lead=more $. I've tried both the JSB Monster's at 25.39gr and Beast's at 33.956gr and have rudimentary tunes for each. I have 4 tins of the 25.39 coming from Pyramid. Once I get them and get a tune going I'll probably post again for a critique of that pellet and tune.

Thanks again.

I’m guessing you are in the ballpark on the reg. You will only need a very low reg pressure with 15.89. Three on the micro hammer adjuster just seems that would make the hammer hit the valve harder than necessary.
The source you watched does it like I did my impact. We may have watched the same guys. To start you open the valve adjuster up past line 5. Then pick a reg pressure. With you shooting 15.89 it’s going to be low. You might even end up at like 85. Not sure how low the impact can effectively run. After setting the reg I then turn the micro way low. With an 85 to 90 reg I would probably turn it down to like 1.5. Then shoot over a chrono and bump the micro adjuster up. Make sure you fire several shots at each setting before you move the micro adjuster. Takes a bit for everything to settle in. You also are looking for an overall trend so that takes several shots. With the valve adjuster wide open your extreme spread may not be the greatest. So as you move the micro adjuster up you are looking for an overall velocity increase. You keep bumping the micro up until the velocity stops climbing. That point is the max power you will get out of a given reg pressure. It will also tell you if you need to add more reg pressure or not. If you reach the plateau and the velocity is lower than you want then you need to add more reg pressure and work the micro up to find the new plateau. You basically work them up together a little at a time so as to stay in harmony. The valve adjuster comes in at then end. With my impact I tuned with the valve adjuster open to about 10-20 fps faster than I wanted. When you hit that spot then start slowly turning that valve adjuster in until you actually cut velocity a bit (10-15 fps). Doing that should really tighten your extreme spread up especially if you did the prior process decent. The valve adjuster is like a backstop. It will limit how far the valve will open as you turn it inwards. When you slightly decrease the velocity with it you are limiting the valve to opening a little less than the hammer pressure wants to open it. Thus making it open exactly the same every time giving tight shot to shot velocities.

 

[Chukar60]

A lot of my confusion about tuning is that I don't understand the adjusters and what they do. (I'm an engineer if ya gotta know.) So let me try it this way.

What does changing the regulator do?

What does changing the micro do?

What does changing the valve do?

Thanks again.

The regulator adjusts plenum pressure. You can increase and decrease it to whatever setting you need to launch your chose projectile. Plenum pressure is what closes your valve.
The micro and macro adjusters determine the force your hammer strikes the valve. This will determine how long the valve is opening and in turn the amount of air getting to the barrel.
The higher the plenum pressure the faster the valve will close and the heavier the hammer strike the longer the valve remains open.
The art of tuning is arriving at a balance or harmony between the plenum pressure and hammer strike at a regulator pressure adequate to launch your projectile at the speed you want it shoot. This balance is what creates small SD’s and ES’s.
The valve knob works very much like a door stop. It prevents over travel of the valve. As another poster mentioned this is NOT a velocity regulator. It will affect velocity but should only be adjusted to the point where you see a small drop in velocity.
You will not master or learn everything you need to know to competently tune your gun from this one thread but, folks here have given good information to work with.
Unfortunately the YT influencers make this look easy and their explanations leave some to be desired. It is not a simple feat to achieve competency and understanding of the process. It is however a rewarding part of shooting air guns especially PCP’s that are made to tinker with. The Impact is the king of the hill when it comes to tinkering. Stay with it and don’t be afraid to ask questions here. Great bunch of people with a vast amount of knowledge and willingness to help. We all started out not knowing.

 

[elh0102]

A lot of my confusion about tuning is that I don't understand the adjusters and what they do. (I'm an engineer if ya gotta know.) So let me try it this way.

What does changing the regulator do?

What does changing the micro do?

What does changing the valve do?

Thanks again.

I'm going to tell you something that you probably don't want to hear. Being new to PCP rifles, you may not have made the best choice for an entry rifle. As an option, put the M4 in the safe for a while and buy a rifle that you can load and shoot without giving a thought to tuning, such as a Daystate Revere, Weihrauch HW100, or RAW HM1000. The M4 will be there when you have gained some basic experience, ready to tune....or sell.

 

[Trucker3573]

You are already on a good path to getting it down. Yes the m4 is a bit complicated but then again not really once you understand the basics. You will get it down. Approach it step by step like I described. The impact is actually pretty forgiving and your intial tune before you close that valve down to cut velocity doesn’t have to be exact. Once you reach that point where you have closed the valve to slightly cut velocity then you can mess with the micro very fine amounts…1-2 clicks at a time up and down to find the real sweet spot. Also should mention that the most important adjustment for your hammer spring tension is that micro adjuster. The big wheel just dictates the range of your tune. How far you can turn it down. This is where the impact in my experience shines. You could easily tune your gun for a heavier pellet with the wheel on 16 and if done well by simply turning down the big wheel shoot something much lighter with some decent consistency. Most guns will not deviate that much from their ideal tuned spot and maintain an acceptable level of consistency.

 

[Plinkalot]

I'm going to tell you something that you probably don't want to hear. Being new to PCP rifles, you may not have made the best choice for an entry rifle. As an option, put the M4 in the safe for a while and buy a rifle that you can load and shoot without giving a thought to tuning, such as a Daystate Revere, Weihrauch HW100, or RAW HM1000. The M4 will be there when you have gained some basic experience, ready to tune....or sell.

It's not that I don't want to hear it, it's that I think it's poor advice.

I learned a long time ago to buy the best I can afford... otherwise wait and save up for it. Buying stuff I don't want is a waste of money.

Having said that, I also buy cheap stuff when it will work as well as expensive stuff. I've got a $180 compressor that works flawlessly. YOMD

 

[elh0102]

It's not that I don't want to hear it, it's that I think it's poor advice.

I learned a long time ago to buy the best I can afford... otherwise wait and save up for it. Buying stuff I don't want is a waste of money.

Having said that, I also buy cheap stuff when it will work as well as expensive stuff. I've got a $180 compressor that works flawlessly. YOMD

I apologize and I'll not interfere with more poor advice.

 

[Plinkalot]

I’m guessing you are in the ballpark on the reg...

The regulator adjusts plenum pressure...

You are already on a good path to getting it down...

Thanks guys for those responses. There's a wealth of info there and it will take some time to digest, and lots of lead!

I found some vids of the internals of PCP guns and I think studying those will also help greatly in my understanding.

I hear and I forget. I see and I remember. I do and I understand. - Confucius

Thanks again

 

[Plinkalot]

I’m guessing you are in the ballpark on the reg. You will only need a very low reg pressure with 15.89. Three on the micro hammer adjuster just seems that would make the hammer hit the valve harder than necessary.
The source you watched does it like I did my impact. We may have watched the same guys. To start you open the valve adjuster up past line 5. Then pick a reg pressure. With you shooting 15.89 it’s going to be low. You might even end up at like 85. Not sure how low the impact can effectively run. After setting the reg I then turn the micro way low. With an 85 to 90 reg I would probably turn it down to like 1.5. Then shoot over a chrono and bump the micro adjuster up. Make sure you fire several shots at each setting before you move the micro adjuster. Takes a bit for everything to settle in. You also are looking for an overall trend so that takes several shots. With the valve adjuster wide open your extreme spread may not be the greatest. So as you move the micro adjuster up you are looking for an overall velocity increase. You keep bumping the micro up until the velocity stops climbing. That point is the max power you will get out of a given reg pressure. It will also tell you if you need to add more reg pressure or not. If you reach the plateau and the velocity is lower than you want then you need to add more reg pressure and work the micro up to find the new plateau. You basically work them up together a little at a time so as to stay in harmony. The valve adjuster comes in at then end. With my impact I tuned with the valve adjuster open to about 10-20 fps faster than I wanted. When you hit that spot then start slowly turning that valve adjuster in until you actually cut velocity a bit (10-15 fps). Doing that should really tighten your extreme spread up especially if you did the prior process decent. The valve adjuster is like a backstop. It will limit how far the valve will open as you turn it inwards. When you slightly decrease the velocity with it you are limiting the valve to opening a little less than the hammer pressure wants to open it. Thus making it open exactly the same every time giving tight shot to shot velocities.

Hey Trucker,

I was working on adjusting my tune with your methodology. I'm starting to understand what I'm actually doing to the gun when I make changes.

One issue I have is my FPS/shot varies so much it's hard to tell when it stops climbing.

The other thing is I don't know what constitutes ES (extreme spread?) and SD (standard deviation).

Is ES +/- from the average? How much above or below the average is extreme?

I'm familiar with SD but don't know what would be considered good/bad for FPS/shot. Plus, for this situation, is it expressed as a number or a sigma value, or what? How do you calculate it?

You've been a real help. I hope I'm not testing your patience.

Anyone else with help/advice, chime in too.

Thanks again.

 

[carlos_hathcock]

The Impact was my first and only PCP so I think if you like the rifle and tinkering you’ll be fine.

I have to say that your projectile is light for such a powerful weapon. It’s like you bought a cannon but your preferred ammo is dried English peas. Shoot what you want but I think your plenum pressure is high probably even for 18-20 grains. Heavier is better in the wind and your rifle should be able to shoot up to 30 grains without modification, just by altering the settings.

Also 50 feet is really close. It’s like you got an Indycar and are trying to set a fast lap time in the garage. I’ll shoot pellets at 50 yards and slugs at 50, 100, and sometimes 150 yards. Your rifle is capable of regularly delivering one ragged hole at 50 yards if you do your part, and the greater the distance the more satisfaction you’ll have when results come.

Enjoy it however it suits you!

 

[Plinkalot]

The Impact was my first and only PCP so I think if you like the rifle and tinkering you’ll be fine.

I have to say that your projectile is light for such a powerful weapon. It’s like you bought a cannon but your preferred ammo is dried English peas. Shoot what you want but I think your plenum pressure is high probably even for 18-20 grains. Heavier is better in the wind and your rifle should be able to shoot up to 30 grains without modification, just by altering the settings.

Also 50 feet is really close. It’s like you got an Indycar and are trying to set a fast lap time in the garage. I’ll shoot pellets at 50 yards and slugs at 50, 100, and sometimes 150 yards. Your rifle is capable of regularly delivering one ragged hole at 50 yards if you do your part, and the greater the distance the more satisfaction you’ll have when results come.

Enjoy it however it suits you!

AFAIK, 50 feet is a national competitive range of indoor .22lr's.

Plus, my "range" is in my basement, is open 24/7, is climate controlled and has food and drink available whenever I want. lol

If you like to shoot outdoors and long range, great... but don't critize those who prefer short indoor ranges.

The M4 should handle any weight pellet. It takes a lot of skill to race an Indy car in my garage... why do you criticize? haha

 

[nervoustrig]

Busy making friends

A friendly bit of advice. This isn’t reddit or X. Not everything is a dig against your judgment or an attack on your character. You are among people who share a very specific common interest, and who genuinely like to help others and share in the hobby. So when a suggestion or opinion or preference runs slightly counter to your own, it is almost always in good faith.