Velocity change overnight?

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Mink

Mink

Member
May 15, 2020
52
2
NY, United States
I recently installed a Huma regulator in my Taipan Veteran Long .22. I set the pressure to 100 bar to shoot JSB 18.1s @ 885 fps. 


I now have ~300-400 shots through it since the install, and have experienced some velocity fluctuations early on that I have chalked up to regulator break in. However, I am still not satisfied with the consistency. 

1) It seems that I cannot rely on the velocity for a given day. For example, when I last put it away (Monday) it was shooting 885 fps. Today, it settled at 860 fps with no changes. It remained at this speed after 30 shots so I had to increase HST to reach desired speed. It seems that everytime I take the gun out to shoot the velocity has shifted.

2) The cold bore shot is ~25 fps lower than my desired set velocity. It takes 4-6 shots for the speed to settle. I tried to resolve this before by lowering the reg pressure from 115 bar to 100 bar, but I am still seeing these annoying fliers. 


Thank you to everyone who has helped out in my previous recent post. I am at the point where I have found the velocity that I want to shoot and am done tinkering with tunes. I just want the gun to deliver my set velocity when I pull it out of the safe. Maybe this is too much to ask for this gun...
 
Are you using the factory power adjuster?

If so try removing the spring and flipping it around the other way. Take a picture and post it be sure to flip that spring around though when reinstalling.

May seem crazy but at this point what else?
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Appreciate the tip @Yo. I am using the factory power adjuster. Out of curiosity, is there a right and wrong direction to the spring? I have taken it out to degas, but it looked pretty darn symmetrical to me, so I didnt pay much attention when I put the gun back together. 


I am no expert but it just seems like the regulator is somehow at fault here, as I never saw these overnight shifts with the stock reg (although I did observe fluctuations which is why I swapped it out in the first place, even though I now know that the fluctuations were likely due to too high of reg pressure for the HST setting). Maybe I got a lemon Huma? Maybe I should reinstall the OEM reg after ~blindly lowering the pressure via the unmarked adjustment ring? Don’t know, running out of ideas. 
 
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I have experienced the same with my gun. I find that I have to tune the HST really close to maximum to get rid of this 20 to 25 FPS lower first shot. I have my velocity at only 2% lower than maximum for the regulator pressure. It's nice to be able to pick a velocity and set the HST to that, but unless you're willing to really fine tune the regulator, you should really set the HST to a velocity the gun wants to be shot for a given reg pressure. I'd suggest for you to just disregard your ideal velocity and increase the HST. Those 18.13gr can remain accurate above 940 - 950 FPS. The way I found the HST setting for my gun is I just increased it bit by bit until I got a rise in FPS by about 10 FPS for the first shot of the day. From there, I reduced it by just a smidgen. It's really a very fine balance with this gun.
 
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I have experienced the same with my gun. I find that I have to tune the HST really close to maximum to get rid of this 20 to 25 FPS lower first shot. I have my velocity at only 2% lower than maximum for the regulator pressure. It's nice to be able to pick a velocity and set the HST to that, but unless you're willing to really fine tune the regulator, you should really set the HST to a velocity the gun wants to be shot for a given reg pressure. I'd suggest for you to just disregard your ideal velocity and increase the HST. Those 18.13gr can remain accurate above 940 - 950 FPS. The way I found the HST setting for my gun is I just increased it bit by bit until I got a rise in FPS by about 10 FPS for the first shot of the day. From there, I reduced it by just a smidgen. If I have the HST set too high, it gets rid of the first shot dip but I noticed the velocities at 230 bars or less start to become affected with some shots being 15 to 20 FPS lower than average. So it's really a very fine balance with this gun.
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Interesting. Thanks for sharing! Now that you mention it, I recall reading that you should use the regulator pressure to adjust velocity, and the HST to adjust efficiency. My only concern is that it seems like the increased TWANG that can be heard and felt with a high HST setting could impact accuracy. Seems like I have heard that you can “hear when a gun is in tune” because it’s a muted THUP more than a loud TWANG. Or maybe that’s just subjective nonsense. 
 
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I have experienced the same with my gun. I find that I have to tune the HST really close to maximum to get rid of this 20 to 25 FPS lower first shot. I have my velocity at only 2% lower than maximum for the regulator pressure. It's nice to be able to pick a velocity and set the HST to that, but unless you're willing to really fine tune the regulator, you should really set the HST to a velocity the gun wants to be shot for a given reg pressure. I'd suggest for you to just disregard your ideal velocity and increase the HST. Those 18.13gr can remain accurate above 940 - 950 FPS. The way I found the HST setting for my gun is I just increased it bit by bit until I got a rise in FPS by about 10 FPS for the first shot of the day. From there, I reduced it by just a smidgen. If I have the HST set too high, it gets rid of the first shot dip but I noticed the velocities at 230 bars or less start to become affected with some shots being 15 to 20 FPS lower than average. So it's really a very fine balance with this gun.
Click to expand...

Interesting. Thanks for sharing! Now that you mention it, I recall reading that you should use the regulator pressure to adjust velocity, and the HST to adjust efficiency. My only concern is that it seems like the increased TWANG that can be heard and felt with a high HST setting could impact accuracy. Seems like I have heard that you can “hear when a gun is in tune” because it’s a muted THUP more than a loud TWANG. Or maybe that’s just subjective nonsense.
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I haven't noticed any "twang" coming from any of my 3 Veterans. That sounds rather odd to me.
 
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I haven't noticed any "twang" coming from any of my 3 Veterans. That sounds rather odd to me.
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I was gonna say the same that I haven't noticed any such sounds on mine either. From the factory 40+ FPE tune to when I had it as low as 27 FPE at one point, all I notice is the ping of the hammer hitting the valve.
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I should clarify that the sound isn’t abnormal, just a louder ping and sharper recoil impulse of the valve being struck hard. I guess I have gotten used to the quieter valve strike of a lighter HST setting, so when I turn it up it feels more violent. But evidently consistency goes out the window when the HST isnt near max. 
 
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Just for reference, at 100b regulator set point on my .22 long, my HST is exactly at 8.75 turns. I measure the HST turns from the first hole on the knob to go to 12 o'clock position immediately after the threads catches. It is getting an extreme spread of 18 FPS (1.87%) and 5.3 SD with the Hades from a combination of 3 sessions with 5 to 11 shots per session for a total of 26 shots so far. I know my shot string only has a low shot count but keep in mind that these 3 sessions are done in the span of 11 days. I'm not willing to waste pellets and air to do a full shot string from max fill until I have totally tuned the gun to deal with the "first shot" syndrome. As a pesting gun, how the gun handles the "first shot" and the subsequent few shots is more important to me than ultra low ES from a shot string done in one full session. Doing a shot string this way takes a really long time because I obviously only get 1 "first shot" per day. I feel I needed to say that so you know what my goals are and what I am trying to achieve with my tune so you're not chasing something totally different if you're tuning for something else.
 
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