First shot lower fps on regulated pcp

Forums PCP Airguns First shot lower fps on regulated pcp

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    hvack
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    I have noticed that on my regulated fx bobcat I get 35-45 fps drop on first shot as compared to the following shots . Is this some what normal for a regulated pcp ?

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    BigTinBoat
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    That likely means you are getting a slight bit of regulator creep. If your gun is “tuned” correctly and the reg is set for like 1500psi. If the regulator creeps up a little over time then when it sits for a while it will be at like say 1600psi. If you strike a valve with the hammer tuned for 1500psi, and there is 1600psi in the valve it will not open as far/fast and there will be less air expelled and the shot will be slower.

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    hsnmz
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    What could cause the regulator to creep and how to correct it.

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    hvack
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    Could it be anything else ? Will I need to replace the reg?

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    Doug
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    Had my Bobcat MK2 tuned by AOA a while back and what they told me was: “We recommend blowing 2 shots off (without a pellet loaded in the chamber) after a full fill, by doing this you will make sure the regulator is functioning with full pressure.  If this is not done you will find the first few shots after a full fill are firing at a lower velocity.”  This is an exact quote that was on my service ticket.  Hope this helps :)

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    captnemo
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    “Doug”Had my Bobcat MK2 tuned by AOA a while back and what they told me was: “We recommend blowing 2 shots off (without a pellet loaded in the chamber) after a full fill, by doing this you will make sure the regulator is functioning with full pressure.  If this is not done you will find the first few shots after a full fill are firing at a lower velocity.”  This is an exact quote that was on my service ticket.  Hope this helps :)

    
+1

    exact quote on my Bobcat …

    my service ticket printed this on mine 
    after regulator replacement in recent bobcat service and complete o-ring job on the whole gun
    by the way  I absolutely love this thing !
     

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    chasdicapua
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    I’ve heard that it takes a shot or two or three to “get on the regulator”. And I experience that with my FX Royale 200. It takes two shots before it settles in.  I’m not sure if this is a problem or just how things are. Doesn’t seem like a big deal to me.

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    BigTinBoat
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    “hsnmz”What could cause the regulator to creep and how to correct it.

    
As Kris has said, the pressure will cause the piston to “embed” in the seat, this causes the pressure to increase. The way to fix it is to replace the sealing seat.
    I experienced this “creep” with a gun I put a bottle on whit a ninja regulator. First shot was always faster. I took the reg apart and sure enough the seat was “embedded”. With the Ninja the “seat” is actually a “ball”. I pushed the “ball” out, rotated it around, and pushed it back in. All shots the same speed now.

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    hvack
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    All good info . Thanks guys. I may just try and live with it . The first shot is 810-822 the second shot is 835-845, third and following is 850-865. Although the other day after over 150 shots I noticed it got as high as 875 fps but averaged 860. First shot is always between 810- 825 after gun has not been shot for 3 hours and up….

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    hvack
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    Update !!!! I finally took the gun apart and heated the lock tight out of the hammer spring adjustment .. After  adjusting the hammer spring , I got it set at 925 fps on 25.4 kings and the initial shots are now the same as all other,,, I am guessing that the spring was set to low !! just an FYI….  My es got better and sd ,,, es=8 sd = 2 over 70 shots…

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    sniperlabyo
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    All the regulator I have work on and tuned they are more consistent when using near or full pressure of the out put of the reg. 

    if reg is properly working:

    lets say your reg pressure is set at 130B then the HSTA is adjusted to get the max speed of 920fps that is your most consistent setting, your 1st-3rd shot will be within your ES.even after is been idle for hours or 1st shot the next day.

    now lets say you lowered the speed to 860fps with the HSTA  without lowing the reg pressure with this setting your 1st shot will be low after its been setting for a while or next morning. 

    Also don’t let the reg pressure drop below pressure setting—always keep it close/regulating. I usually fill 10-20b before its.goes off the reg. this way the 1st shot will be more consistent with your ES after the fill.   

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    hvack
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    “sniperlabyo”All the regulator I have work on and tuned they are more consistent when using near or full pressure of the out put of the reg. 

    if reg is properly working:

    lets say your reg pressure is set at 130B then the HSTA is adjusted to get the max speed of 920fps that is your most consistent setting, your 1st-3rd shot will be within your ES.even after is been idle for hours or 1st shot the next day.

    now lets say you lowered the speed to 860fps with the HSTA  without lowing the reg pressure with this setting your 1st shot will be low after its been setting for a while or next morning. 

    Also don’t let the reg pressure drop below pressure setting—always keep it close/regulating. I usually fill 10-20b before its.goes off the reg. this way the 1st shot will be more consistent with your ES after the fill.   

    
Right …..This is why I am thinking that my factory hammer spring was set to light,,now with it turned out 1.75 from full clockwise I no longer get the slow first shot…If it was reg creep Wouldn’t I still be getting slow first shot ?

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    Alex
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    It’s because the last shot you fired was under regulated pressure so even if you charge your gun back up to whatever psi you need, your regulator will still have that same under regulated air in it. My fx royale did the same thing to me and i was wondering what it was. I recommand you firering one shot after filling it so the regulator and the air chamber are at the same pressure.

    Alex

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    hvack
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    “Alex”It’s because the last shot you fired was under regulated pressure so even if you charge your gun back up to whatever psi you need, your regulator will still have that same under regulated air in it. My fx royale did the same thing to me and i was wondering what it was. I recommand you firering one shot after filling it so the regulator and the air chamber are at the same pressure.

    Alex

    
I know what your saying ,, but you need to read the rest of the post’s .. I never fire the gun down to were it comes off of the reg… It was slow on the first shot after setting for a while or over night,  all the time.

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    sniperlabyo
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    Reg creep mean the pressure is leaking pass the Delrin seat unable to stop the supply end, there it will over pressurize the regulated chamber pass set point till it force the valve stem to seal. Let say the reg is set at 130b by the time it stop creeping at 150b and seals it self —> but now the 1st shot will be high not low 

    There are 4 seals on the regulated chamber if you have a leak  it will shoot the 1st shot low. when pressure drop low enough the reg will open up to maintain the reg pressure it will keep doing this till you notic a drop in pressure on your gauge. 

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    BigTinBoat
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    “sniperlabyo”Reg creep mean the pressure is leaking pass the Delrin seat unable to stop the supply end, there it will over pressurize the regulated chamber pass set point till it force the valve stem to seal. Let say the reg is set at 130b by the time it stop creeping at 150b and seals it self —> but now the 1st shot will be high not low 

    There are 4 seals on the regulator chamber if you have a leak  it will shoot the 1st shot low. when pressure drop low enough the reg will open up to maintain the reg pressure it will keep doing this till you notic a drop in pressure on your gauge. 

     

    Ernest – I know you know your stuff, but you are mistaken in this situation. 
If the gun is tuned to get the max FPS (without wasting air) out of 130B and then you shoot it with 150B the velocity will NOT be higher. Reason being is the same as why an unregulated PCP has a “bell curve” and increases in velocity (as the pressure drops) before then reaching a peak and decreasing.
    Think of it as a gun that the top of “curve” is at 130B. At 180B all the way down to 130B the velocity will be increasing. After the pressure drops below the 130B the velocity will then start decreasing.
    This is exactly what I explained in the beginning.

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    sniperlabyo
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    Wow I should have explain it in more detail about regulated AG it can be misunderstood.

    Your right in what you stated and so I’m I —>

    but we will never know the situation till we know reg pressure that the hammer
    spring can handle till FPS start to drop.

    when I tune a Regulated AG, I test the reg in 5b increments starting at 130b and adjust the hammer spring till I find the highest Speed, I keep doing that till the FPS start to drop– let say 150b now I now the max pressure the hammer spring can handle/before it can’t open the valve fully.

    to minimize creep I set the reg 5-10b below the max pressure the HS can handle in this case 150d—so I would set it at 140b.

    if the creep pressure went up to 5-10 bars and not knowing the HS max speed the 1st shot is going to be high.

    So I recommend not to adjust the reg without proper test gear, you could over adjust and not know it—then you have an unregulated AG. Also I test the reg in what pressure it will fail to regulated—not knowing before adjusting will give you gray hairs.

    Thanks for your knowledgeable comment BTB

     

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    hvack
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    What my gun was doing was,,, after sitting a while or all night I would go out and shoot it over the crony, first shot anywhere from 820 to 838 , using 25.4 kings , then after 2-3 shots would settle out at 860-868, sometimes 875 Extreme spread was 11 to 22 standard deviation was 5 to 9 …. Then I turned the hammer spring up and now anytime I pick up the gun and shoot it’s 925-930 es= 8 ,, sd = 2 .. went from 42-43 fpe to 50-52 fpe and no low first shot ….. didn’t touch the reg ….

      People were telling me it was the reg or reg creep ,,, IDK why it doesn’t do it NOW ????

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    sniperlabyo
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    seen that a lot, The HS is to fine tune the reg consistence not the other way around!

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    hvack
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    “sniperlabyo”seen that a lot, The HS is to fine tune the reg consistence not the other way around!

    
Thanks for your input .  :)  So in my case you are thinking that I did not have a regulator problem , just to light of a hammer spring ?????

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