First shot poi is low sometimes w/ reg. rifle (good video explaining why)

[Tweeter]

I have wondered why sometimes my first shot is way off target on a couple of my guns that were regulated.  I found this video on the subject and figured I'd share...

[Tucobenedicto]

Interesting,i noticed some regulator creeping after full pressure filling on my regulated Prod sometimes.

[T-Higgs]

I have wondered why sometimes my first shot is way off target on a couple of my guns that were regulated.  I found this video on the subject and figured I'd share...

Justin,
You could nat have posted this at a more perfect time. Being new to PCP, this has been on my mind for over a week because of low velocity (cold bore) shots I would have on occasion.  Makes perfect sense and a visual description is 1000X easier to understand especially when I've never worked on a regulator or even had one in my hands.
Much appreciated,
Higgs

[Gerard]

Interesting stuff, though I'm not sure how much it explains my situation. I shoot a .22" QB78D with the full tube for a plenum and a 13ci Ninja bottle with belleville discs set to about 1200psi output. I've tuned the valve and SSG such that I get about 125 shots at 19.8fpe average with 18.13gr JSB - about 700fps average, from around 703fps initially then gradually droppeing to around 685fps for the last few shots. But depending on how long I've let it sit, my first shot can be as high as 725fps. Maybe 715fps if I've shot it within the past couple of hours. For home use that's not a worry for accuracy as none of the squirrels I shoot are far enough from the house that a millimetre or two vertically is going to mean anything. Dead is dead. But for HFT it could be significant so I take one or two shots just before a match to clear the pipes and get my first competition shot down to 700fps, if the first target is further than about 20 metres. Since I only ever use an FX pump to fill, this variation can't be related to filling speed. Has to be regulator creep.

I have a Lane regulator in a 2240 with a HiPAC - set it up for my son for HFT and mostly plinking. It gives about 25 shots within an 8fps ES and has no initial higher or lower velocity shot, just very even until off-regulator then drops maybe 15fps over three shots, then much more rapidly. Seems the Lane regulator set to about 60 bar output is very stable... which kind of makes me wish there was a Robert Lane device to fit a Ninja tank. Oh well, the ~15fps ES (after that first shot) with my QB isn't so bad. At least out to 40 metres I don't see it making a lot of difference.

[Tucobenedicto]

If your regulator creep,probably the ball shaped seal leaks, assumed the bellevilles springs are properly setted and not near "coil bind".
in one reg i had i solved changing the bellevilles switching to hardest ones changing the arrangement and shims.
A ninja rebuild kit can eliminate leaks with a ten bucks expense.

[Gerard]

The spring washers aren't all that tight, spacing is almost identical to stock but with the arrangement different to increase output pressure - as supplied mine was outputting about 570psi with a coil spring and two shims. Shimming that I managed to get up to about 950psi so I changed to belleville washers arranged like this - )))(())(())(( - and that got me to 1200psi. Two inspections since setting that up have shown zero glitches on the ball seal, it's perfect, and I'm using urethane seals and Corning silicone grease. 'Coil bind' happened when I tried adding one more belleville, so that's not happening as it is. It's working well enough as it is, I'm not complaining, just idly curious about this first round bump in power. Probably just some very subtle leak or set of leaks in the Ninja regulator as it isn't a big jump in velocity, and never gets over 725fps even if un-fired for two weeks. The gun puts pellets inside a dime at 30 metres and I don't demand anything more. Of course I'd love it if I could shoot sub-MOA but with a 13.4" QB barrel I don't think that's likely. With a factory length barrel I got a tighter ES and an extra 70fps, but that's impossible to transport in a backpack (it's set up as a TDR) and too much power for the HFT targets anyway.

[nervoustrigger]

In his video, Robert is describing something different than regulator creep.  He was describing what occurs when the gun is operated down below the regulator setpoint, and how refilling affects the way the valve closes which results in a pressure that is slightly higher or lower than the normal setpoint.  To avoid that issue, all you have to do is refill before the pressure dips below the setpoint.

Creep is a tendency for the valve to not completely seal when it reaches the intended setpoint, but instead continue to slowly flow high pressure air into the regulated plenum.  Eventually, the pressure gets high enough to completely seal off the valve seat.  To use an example, let's say you have a target setpoint of 1500psi.  When you fire a shot, the pressure in the plenum falls to 1200psi.  The seat opens and quickly returns the plenum to 1500psi within 5 seconds and almost seals completely but not quite.  Then if you wait, the pressure may slowly creep up to 1700psi over the course of a few minutes or a couple of hours. 

Regulator creep may be little more than a nuisance for shooting paper but it is real problem for a hunting situation where you may only get one shot.

In the world of paintball regulators, Ninja's design is excellent.  A plastic ball (appears to be Delrin) on the regulator piston seals against the valve seat which is shaped like a small truncated cone.  This design works really well.  The setpoint is reached within a few seconds and does not continue to creep.  Eventually after many thousands of cycles it might begin to creep because the ball begins to wear, and you can usually knock it out and flip it over and start anew.  If and when it happens again, you can get a rebuild kit for about $15.

Other paintball regulators I've tried which use a flat seal have been prone to creep.  Because the designs are so similar, sometimes you can replace the piston with a Ninja piston from the rebuild kit and overcome the problem.

For in-tube regulators, you're at the mercy of the particular design.  Like Ninja's, a good design won't creep.  If it does creep and you plan to hunt with it, I would contact the manufacturer to see what can be done to remedy it.

[Gerard]

Perhaps I wasn't clear? Mine's a Ninja, and uses the little delrin (or maybe nylon?) ball seal. One side actually did take an impression from the seat, when I had a faulty 1.8k burst disc blowout at around 1400psi, so I flipped it to the clean side of the seal and it's stayed smooth ever since, no trace of deformation when inspected after about 1000 shots and again after maybe 4000. It doesn't continue to creep, as I said, it just tops out around 725fps. This creep happens at anywhere from 1200psi to 3000psi, and doesn't have any relation to the last time I filled it with the FX pump; it just gradually climbs to 725 over a few hours then stays there, sometimes for weeks. So I can count on my 'one shot' for hunting being a little bit hot, meaning in my case that I would have to start worrying at something over 30 metres. Since I don't 'hunt' per se (I've been vegetarian since 1979) and only shoot rats (with a much lower powered regulated carbine and NV setup) and squirrels invading the garden, never further than about 20 metres, this slight change in velocity isn't an issue for me. It becomes an issue for FT targets beyond 30 metres, so I dump a couple of shots before a match to bring it down to around 700fps, and the creep is slow enough (maybe 10 minutes before it even gets to 710fps) that it won't become a problem during a match.

Sometime I'll no doubt get a new seal for the Ninja bottle's regulator and swap the O-rings and bellevilles, but for now this small inconsistency at the start of any shooting session isn't a serious issue so no rush on that.

[nervoustrigger]

Sorry, Gerard, I wasn't directing the reply to you.  It was just a general reply to the subject of the thread.

[Motorhead]

Would add this ....
If one spends some time in finding the optimum pressure setting and both HIGH & LOW ends of the ideal pressure and set the gun at or slightly under the normal optimum pressure you won't get a velocity jump or dive if reg has creeped a few 100 psi.

Typical is when your tune has you on the front end of optimal pressure and any increase in plenum pressure from creep has the valve harder to open and you get a soft shot.  If tuned on high side of optimal pressure you can get a HIGHER velocity shot simply because the valve still opens the same but higher pressure within the plenum drives the shot quicker.

* In simpler terms ...
For a given plenum pressure, when your hammer strike is light any increase in pressure within plenum the valve opens HARDER and you will see a lower velocity shot.
If you have a heavy hammer strike already and valve is readily getting opened, an increase in plenum pressure won't have much if any effect in valve opening but will allow higher pressure to launch the pellet & thus why an increase in velocity happens.
Closer your hammer strike is to the optimal peak less because the influence of slightly lower or higher pressure within plenum.

Smaller the plenum is, greater is the velocity variance one will see with pressure changes.

Sadly no real Black / White to this being there are many other factors also contributing to how subtle pressure changes effect some guns and not others.

[Tweeter]

I had it happen to me way back with my first pcp, a Nervoustrigger tuned Qb-79 hpa.  Since then I've heard the issue mentioned here and there and also heard a well known you tuber say it happened to his cricket and he didn't know why.  I've always kind of wondered about it and now after watching the video it all makes perfect sense.   

[Tweeter]

Will temperature affect the pressure output of your regulator just like it does to the air cylinder?  I know when I fire up the wood stove my gun jumps up about 10bar...

[nervoustrigger]

Will temperature affect the pressure output of your regulator just like it does to the air cylinder?  I know when I fire up the wood stove my gun jumps up about 10bar...

It has an effect but it's a little more nuanced.

A regulator functions by allowing air to flow until the plenum increases to a certain pressure.  Once that pressure is reached, the flow of air should cease.  So the effect differs depending on which direction the temperature goes.

If you were last shooting your gun in a warm environment and then move to a colder environment, the air in the regulated plenum will cool down and its pressure will fall.  In turn, the regulator will respond by allowing air to flow in to top it off.  How discriminant it is will vary due to a number of subtle factors, but suffice it to say this is generally a self-correcting scenario.

On the other hand, if you were last shooting in a cold environment and then moved to a warmer environment, the air in the regulated plenum will warm up and increase in pressure.  This behavior will only serve to close the regulator seat even harder.  Thus the pressure will stay high.  Depending on how your gun is tuned, it may shoot faster or slower or remain virtually the same.  After a shot or two, it should be back to normal.

[Tweeter]

Thanks Jason, great description I never thought of it that way.  Most of my shooting here in Maine involves me leaving a warm house to shoot outside in the cold.

[TunedAccuracy]

In his video, Robert is describing something different than regulator creep.  He was describing what occurs when the gun is operated down below the regulator setpoint, and how refilling affects the way the valve closes which results in a pressure that is slightly higher or lower than the normal setpoint.  To avoid that issue, all you have to do is refill before the pressure dips below the setpoint.

Creep is a tendency for the valve to not completely seal when it reaches the intended setpoint, but instead continue to slowly flow high pressure air into the regulated plenum.  Eventually, the pressure gets high enough to completely seal off the valve seat.  To use an example, let's say you have a target setpoint of 1500psi.  When you fire a shot, the pressure in the plenum falls to 1200psi.  The seat opens and quickly returns the plenum to 1500psi within 5 seconds and almost seals completely but not quite.  Then if you wait, the pressure may slowly creep up to 1700psi over the course of a few minutes or a couple of hours. 

Regulator creep may be little more than a nuisance for shooting paper but it is real problem for a hunting situation where you may only get one shot.

In the world of paintball regulators, Ninja's design is excellent.  A plastic ball (appears to be Delrin) on the regulator piston seals against the valve seat which is shaped like a small truncated cone.  This design works really well.  The setpoint is reached within a few seconds and does not continue to creep.  Eventually after many thousands of cycles it might begin to creep because the ball begins to wear, and you can usually knock it out and flip it over and start anew.  If and when it happens again, you can get a rebuild kit for about $15.

Other paintball regulators I've tried which use a flat seal have been prone to creep.  Because the designs are so similar, sometimes you can replace the piston with a Ninja piston from the rebuild kit and overcome the problem.

For in-tube regulators, you're at the mercy of the particular design.  Like Ninja's, a good design won't creep.  If it does creep and you plan to hunt with it, I would contact the manufacturer to see what can be done to remedy it.

This.
Simplified: Don't let your gun fall off the regulator.