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Tuning First Attempt at Tuning an Airgun

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J

Jason

Member
Jun 30, 2015
60
1
Louisiana, United States
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I have a new FX Crown Continuum MK2 and am trying to harmonically tune it by following the instructions in this video: https://m.youtube.com/watch?v=xxrDZmB5egU

The instructions are really clear and I was able to follow them step by step.

However, unlike in the video, my average velocity did not jump up and down initially before leveling out and then dropping off.

I included a picture of what my velocities did. I started off with the hammer spring adjustment screw maxed out and backed off a quarter turn each shot.

The video recommends setting the hammer spring where the velocity is someone consistent. I didn’t have much to chose from so I set it around shot 23.

Afterwards, I took a 15 shot string with an average velocity of 878, an extreme spread of 11.5 fps, and a standard deviation of 2.85.



A couple questions:

Is a spread of 11.5 acceptable and a standard deviation of 2.85 acceptable?

Did I possibly do something wrong while adjusting the hammer spring since the velocity did not level out like in the video?



Also, I’m using 18.13 grain JSB pellets with a reg pressure set at 145 bar.

I appreciate any thoughts.



Jason














 
Your SD and ES are awesome. Anything that low will not even come close to negatively affecting your accuracy. The only thing I noticed is that your reg. is set pretty high for shooting 18.13 gr. at 878. I would think you could have the same velocity with your reg. set much, much lower, which would give you a bunch more shots, like 1/3 more. Just a thought. Have a good one.

Stoti
 
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It takes 30,40,fps or more to really affect your accuracy much, so your ES is really great. Hopefully someone with a .22 shooting the 18.13gr will chime in and tell you how they have their gun set up. I was guessing you could have your reg. set at 90bar or so and get the same velocity. That was just a guess but if so, you would increase your shot count by about 1/3. Just guesstimating but it would be substantial.

Have a good one.

Stoti
 
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Yes, I have the 380mm barrel on it right now.
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I wouldn’t go for any more speed with tiny Tim on your gun. You are probably right on the edge of wasting air right now. Don’t be afraid to try 15.89’s that will easily get you in the 880-900 range and allow you to relax the gun a little more. But if those 18.1’s shoot good, stick with them.
 
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Your SD and ES are awesome. Anything that low will not even come close to negatively affecting your accuracy. The only thing I noticed is that your reg. is set pretty high for shooting 18.13 gr. at 878. I would think you could have the same velocity with your reg. set much, much lower, which would give you a bunch more shots, like 1/3 more. Just a thought. Have a good one.

Stoti
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Hm... I find that having a reasonably high reg. pressure with short valve dwell increases my shot count. I tuned mine using the same method, but first tuned the regulator pressure. MAX hammer, and find where power starts to fall off on the regulator, then dial it back maybe 5 bar behind peak power. THEN adjust eh hammer to find peak power, and dial it back a bit under peak output.

My 380mm shoots 18.13 @ 920fps here (50fps above factory ports, mine are massaged), and is significantly quieter than if I adjust hammer/reg. pressure upward from here. Not very much below overall peak output for the gun in this config either. ~100 or so shots on 480cc tank
 
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High reg. pressure is a relative term. What’s your reg set at? What do you consider. “high” for a .22 with a 18.13 pellet? I agree with what you’re saying, just curious how much reg pressure you need for a fast dwell time with an 18.13 pellet in .22? Don’t have a .22 anymore, that’s why I said I hoped someone like you would chime in. 

Stoti
 
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Ok, so, on my regulated guns I often settle in around 135 bar. I had thought I was in the 135 bar range on the Crown. But I recently knocked my gauge out of whack. Leading me to suspect it was never right in the first place.

Well, I've been shooting blind. I did get some huma gauges in (after trying a new fx gauge and it being bunk)... took the time to install them just now.... It actually is at 135 bar that I'm right in where I'd like to be. But I can also get the same power output around 125 bar. (of course with longer dwell time) 130 bar is pushing 18.13grs at 950fps thru the ported 380mm barrel 😲 this is not a mkii Crown. 135 bar is seeing 915-920fps

I only said reasonably high because a lot of impact guys are tuning for 100 bar give or take. Now, what pressure will give the desired result is really going to be dictated by that particular gun, and whatever the gauge is deciding to read.



DSCF5628_edited.1610970837.jpg




 
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I used to have my Impact set up with a high reg. pressure(160bar), high hammer spring pre load(almost max), yes the dwell time is faster, probably 1.5-2milli seconds but shot cycle was too harsh and it wasn’t the most accurate, even backed off to 95% of max. I’m not big fan of chasing efficiency as much as accuracy and back then maximum power. I was just suggesting Jason could turn down his reg. a bit with the smaller diameter, lighter pellets, still have a plenty fast lift and dwell time, increase efficiency and retain accuracy .Like I said, I was guessing though, don’t have a .22. You know the game, it’s all a trade off. I’ve been shooting a lot more pellets with my boys lately than slugs and your comments got me thinking about a couple of things. I’m off today for the holiday, so I’m going to try a couple of things. I have digital gauges that show the amount of air used per shot. I haven’t utilized them fully to check high reg. pressure, high hammer spring pre load for a fast lift-dwell time and efficiency vs. turning down the hammer spring tension, increasing dwell and how it effects accuracy and air used per shot. Then doing the same thing but opposite with a longer pulse to see how it effects accuracy, power, shot cycle and efficiency. I’ll also tighten the valve adjuster throughout the process to see the effect of efficiency, accuracy shot cycle with both the fast and slow dwellI. I’ve tuned my gun so many times but because efficiency is usually looked at after accuracy and power, I’ve never really checked the air used per shot and the correlation between accuracy, power, efficiency, dwell, shot cycle, etc... It will be a cool learning experience. Thanks.

Stoti
 
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I used to have my Impact set up with a high reg. pressure(160bar), high hammer spring pre load(almost max), yes the dwell time is faster, probably 1.5-2milli seconds but shot cycle was too harsh and it wasn’t the most accurate, even backed off to 95% of max. I’m not big fan of chasing efficiency as much as accuracy and back then maximum power. I was just suggesting Jason could turn down his reg. a bit with the smaller diameter, lighter pellets, still have a plenty fast lift and dwell time, increase efficiency and retain accuracy .Like I said, I was guessing though, don’t have a .22. You know the game, it’s all a trade off. I’ve been shooting a lot more pellets with my boys lately than slugs and your comments got me thinking about a couple of things. I’m off today for the holiday, so I’m going to try a couple of things. I have digital gauges that show the amount of air used per shot. I haven’t utilized them fully to check high reg. pressure, high hammer spring pre load for a fast lift-dwell time and efficiency vs. turning down the hammer spring tension, increasing dwell and how it effects accuracy and air used per shot. Then doing the same thing but opposite with a longer pulse to see how it effects accuracy, power, shot cycle and efficiency. I’ll also tighten the valve adjuster throughout the process to see the effect of efficiency, accuracy shot cycle with both the fast and slow dwellI. I’ve tuned my gun so many times but because efficiency is usually looked at after accuracy and power, I’ve never really checked the air used per shot and the correlation between accuracy, power, efficiency, dwell, shot cycle, etc... It will be a cool learning experience. Thanks.

Stoti
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It's all about how far down the rabbit hole you want to go, lol. The name of the game ultimately ends up being try it, and see, lol. I've been pretty tempted to get a test gauge myself to get a better eye on the situation. I did want an edmu, but not after reading user experiences.

Typically, though, I will tune my guns with sound signature in mind. Especially on a short barrel. You can get a respectable amount of power, but it's easy to overrun the barrel volume. (huge muzzle blast for maybe 30-40 fps gain, lol.) I think the last one I tuned, I compromised a bit, because I was getting a bit high up in the pressure range to justify the reduction of dwell/report. Dialed it back to where power has a flat taper off of the regulator. Got a good 10 extra useable shots just on falling off the reg. 
 
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I used to have my Impact set up with a high reg. pressure(160bar), high hammer spring pre load(almost max), yes the dwell time is faster, probably 1.5-2milli seconds but shot cycle was too harsh and it wasn’t the most accurate, even backed off to 95% of max. I’m not big fan of chasing efficiency as much as accuracy and back then maximum power. I was just suggesting Jason could turn down his reg. a bit with the smaller diameter, lighter pellets, still have a plenty fast lift and dwell time, increase efficiency and retain accuracy .Like I said, I was guessing though, don’t have a .22. You know the game, it’s all a trade off. I’ve been shooting a lot more pellets with my boys lately than slugs and your comments got me thinking about a couple of things. I’m off today for the holiday, so I’m going to try a couple of things. I have digital gauges that show the amount of air used per shot. I haven’t utilized them fully to check high reg. pressure, high hammer spring pre load for a fast lift-dwell time and efficiency vs. turning down the hammer spring tension, increasing dwell and how it effects accuracy and air used per shot. Then doing the same thing but opposite with a longer pulse to see how it effects accuracy, power, shot cycle and efficiency. I’ll also tighten the valve adjuster throughout the process to see the effect of efficiency, accuracy shot cycle with both the fast and slow dwellI. I’ve tuned my gun so many times but because efficiency is usually looked at after accuracy and power, I’ve never really checked the air used per shot and the correlation between accuracy, power, efficiency, dwell, shot cycle, etc... It will be a cool learning experience. Thanks.

Stoti
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This statement is worth its weight in Bitcoin!!! 

I also have a feeling that FX has create a new "language" with the M3 and its various numeric adjustments that can be understood, shared and replicated across the M3 platform. It appears we are moving in the right direction. Potentially answering how these variables interact and give them some sort of universal numeric value to achieve a desired result in a given caliber. Just thinking out loud 😁

Have a great weekend and give your Mom a hug and a kiss.

Patrick


 
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