Reply To: How much effect of a consistent regulator on accuracy?

Forums PCP Airguns How much effect of a consistent regulator on accuracy? Reply To: How much effect of a consistent regulator on accuracy?

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nervoustrig
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The 97% is not a precise number.  If something is way out of balance, it may be worthwhile to play around with the regulator setpoint and see how the gun responds, or better still, see how it behaves in unregulated form to establish a baseline.  But it works well in most cases.

If you want to tune to a specific velocity, yes it's a good idea to adjust the regulator's setpoint so that the 97% figure gives you the velocity you want*.  Not so much for efficiency but for consistency (holding a tight ES).  Granted it will be much more efficient than going for peak velocity but not as efficient as backing way down, which brings us to your other question.

If your max velocity is 920fps and your goal is 850fps, that works out to about 92%.  That is not unreasonable and it may be that the gun will hold a tight ES as long as it's on the regulator.  However it will be more sensitive to a velocity loss if the regulator creeps and it will also experience an increase in velocity as the pressure falls below the regulator's setpoint. 

The mechanics at play are easier to understand if we look at a more extreme example.  Let's say the max velocity is 900fps and the goal is 700fps.  To downtune that much by simply backing off the hammer spring tension, what is happening is the hammer is barely knocking the valve open.  Really low lift and very short dwell.  The valve is open for a teeny tiny fraction of the time the pellet is in the barrel and accelerating.  Tiny variations in friction lead to wild velocity swings.  If we kept going down further, we would eventually reach complete valve lock.

 

With that said, this type of tune is very efficient if you can tolerate the extreme spread.  Very efficient also means very quiet.  A modest de-tune can be quite useful for back yard plinking or discreet pest removal in a suburban setting.  Just not something you'd generally want to do for 50+ yard duty. 

* The other way to shift the velocity up or down is to change the porting (the cross-sectional area of the path the air follows).  You can do one or the other or a combination of both.  For example when adding a regulator to a rifle that was designed as an unregulated rifle, it's pretty typical to increase the porting.  That way it can produce as much (or more) energy than it previously did, despite now operating at a lower pressure.