Are we better off setting our regulators to lower psi?

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zebra

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Sep 29, 2015
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New York
I'm trying to understand the benefit of setting the reg to higher PSI output vs setting it lower and increasing the hammer spring tension to compensate. 

I am looking at the point where some of my air rifles "drop off the reg" and wondering if I would get more shots on the reg if the reg was set lower with a heavier hammer spring to deliver the same volume of air?

I was watching the review of the 9mm Ataman carbine (which isn't actually a carbine at all) on the PA site and it seemed to drop off the reg at 180 bar. This gave the guy around 10 shots on the reg which would seem about right for a 9mm until you consider that he started with a 300 bar fill. 

I fill from a 4500 psi tank and after the first few fills, most are closer to 3000 psi than 4500psi. I would end up with less than 3-4 shots on the reg for most of the fills with a 9Mm Ataman unless it was tuned differently. 

Maybe a tuner or someone with an Impact can comment and let me know if a lower reg setting plus a higher hammer spring tension allows you to use more of your air reservoir on the reg (I.e. More shots per fill)?

It seems wrong somehow to have half a tank of air but no shots left..
 
You could lower the Reg pressure to increase shot count if you are willing to sacrifice speed and distance.

Spring tension increase (& fps increase) will diminish at a point. As for valve adjustment (on Impact), that's dependant on the pressure - again after a point it'll just be wasting air.

What cal are you shooting? And what's the maximum distance you target/hunt?
 
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Most of my air rifles are 25 cal but the question is a general one. For any caliber, I want to know what happens if, for example, you dropped the reg from 150psi to 120psi and then increased the hammer spring tension until the first shot produced the same energy as before the reg was adjusted. In that scenario, do you get more shots before It drops off the reg. 
 
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If a consistent high shot count is desired, setting the regulator to a lower operating pressure likewise requires adjustment of the hammer and valve spring. You can set the regulator to operate at a lower pressure and increase the tension on the hammer spring, but you are going to seriously decrease air efficiency even though such setup is able to produce a tight spread. In my opinion, the best tune is one that allows optimum shot count while achieving maximum air efficiency. From experience, the best way to attaining this is by adjusting all three: the regulator and the hammer and valve spring.

To give you an idea of how efficient a PCP can be when all three parts are working together harmoniously, when I had set my Cricket's regulator working pressure to 50 BAR (or 60 BAR as I don't have a reg tester) to shoot at 8-11 FPE but left the hammer spring tension the way it was when the regulator was set to 130 BAR, I only managed to get an extra 55 shots from the initial 70 shots I was getting at high power. However, when I swapped out the high-power spring to the low-power spring that came with the gun and properly set the hammer spring adjuster knob (counterclockwise) and valve spring tension (to less tension) until I could achieve a maximum spread of 10-13 FPS (shooting 14.3 gr. pellets at 525 FPS), I was able to get 430 shots from 220-60 BAR! And that's with pellets straight from the tin. That's a 244% increase from 125 shots! (70+55) In my mind, that is a serious bump in shot count.

The idea behind the ability to have a PCP shoot consistently with a low operating pressure from the regulator is simply by keeping the air in the regulated air chamber as close to the intended pressure after consecutive shots. The way to achieve this is to make sure that the hammer and valve spring tension is tuned/mated to open and close the valve quickly enough while emitting a consistently metered shot charge--using as little air as possible--until the pressure in the air tube drops below the pressure in the regulated air chamber. 
 
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Very simply, I modify my valves to flow tons of air and couple that with a heavier spring or more preload. Then, when setting up the regulator, I have to drop reg pressure rather low to get the power down, but results in tons of shots and really great efficiency. I have a regulator in a .177 set at 78 bar and it gets 100 shots on a rather small airtube but still makes 19fpe.
 
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Does this mean you would get more shots without a noticeable drop in power as long as you also adjusted or modified the valve and / or valve spring along with the hammer spring and reg?

It sounds like both of you have achieved a meaningful improvement over the stock regulator settings by making adjustments that allow you to utilize more of your air reservoir before dropping off. 

Am I right in assuming that a similar improvement can be made with larger calipers (albeit with a smaller number of overall shots than the smaller calibers)?

When my guns drop off the reg, it doesn't usually mean a sharp drop in energy. They just lose their consistency because they don't have enough pressure to operate the reg but they do have enough to maintain similar pellet speed for another 10-15 shots before a noticeable drop.
 
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If you lower the reg set point and increase the hammer energy so the rifle is shooting on the plateau instead of the knee you will have lower efficiency and a reduced shot count. Once you are using enough hammer energy to be on the plateau the velocity wont increase more than 10 fps or so and the more energy you apply the more wasted air you will dump out of the muzzle. The point of a regulator is to keep the ES tight but it also allows you to tune the rifle to get the exact amount of air needed to get the velocity desired without wasting any air. At least thats how a well tuned rifle with a reg works. Once you start increasing hammer energy without increasing reg set point or balancing the valve you begin to use more air than the barrel length will allow to increase speed wasting that air. It would be best to set the reg to the set point required to get the velocity needed while still being tuned on the knee instead of the plateau. So a complete balancing of the valve and hammer energy would need to be done for drastic changes to keep the highest efficiency.
 
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Maybe I missed something.

A regulator maintains the "firing" chamber pressure to some specific PSI. For example, mine is set for 2,100 PSI, or about 145 BAR. Thus the shot to shot consistency (FPS) is VERY good, and that is the main (if not absolute) reason to have a regulator. 

This is juxtaposed with the setting of the hammer spring preload, whether it be a simple one, or an SSG (or similar). Whatever the hammer spring tension, the ultimate limit to FPS and/or FPE and/or shot count is reliant on the maximum firing chamber pressure, the weight of the pellet, and the volume of the high-pressure chamber. Obviously, these settings are codependent, but it should be clear which does what. 
 
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I am well aware of what everything does and the reason for their existence. 

This is is purely a question about using more of the air reservoir before dropping off the reg and getting more shots per fill. 

Adjusting the hammer spring on my rifles alters the power output up or down without any other adjustments. Within reason, it is possible to achieve the same power with the reg set lower. So I want to know if that can be used to tune for a greater number of consistent shots before dropping off.

We know it is possible for PCP guns to be run off lower pressures than what many of them are run at. 
 
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Its only possible to gain more shots by lowering the reg set point if its still tuned on the knee and not on the plateau. If lowering the set point and raising the hammer spring pre load causes excess dwell then its going to have less shots. Once its on the plateau increasing the hammer pre load only causes excessive dwell time causing wasted air and lower shot count. Theres no way around that. You could increase the valve spring tension but then what are you accomplishing?
 
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LDP's explanation is spot-on. However, I'd like to expound further from my previous post, which I think is congruent with LDP's ideas. 

The key to getting the maximum amount of shots first starts with deciding on a power level that is lower than maximum yet sufficient enough to satisfy your shooting needs. Then it's a matter of adjusting your regulator's output to the point in which you are able to shoot at your desired velocity/pellet energy level. If your valve spring tension is adjustable (like on guns like the Cricket or Vulcan) start with a medium to tight (compression) setting, while keeping in mind that too much tension results in valve lock and too little results in the likelihood of the tank dumping all the air out due to its inability to seal it in. There is a happy medium to be reached here. You should also start with the tension of the hammer spring high as well. If the velocity is above that which you've decided on, decrease the tension on the spring. If, in such a case, you've backed out the adjustment of your hammer spring knob all the way and are still getting high velocities, you will need to use a lower power spring. Once you've reached your target velocity (no pun intended) keep backing out the adjustment knob to further decrease spring tension while still being able to retain the desired velocity.

Now here's the not-so-tricky part. Your goal should be to have a setup that, when the regulator falls below its end-working pressure, the remaining charge in the air tube (unregulated air) allows for a consistent power curve and that the hammer and valve spring tension is tuned to work harmoniously with it to still produce consistent shots. Remember, at this point the regulator piston will no longer close and seal off the unregulated air. For clarification, think of an unregulated PCP that is being shot within the sweet spot of its curve. You want to make sure that the shots coming from this current state of the air reservoir is able to give you the remaining "unregulated" but consistent shots and not those that exhibit a sharp velocity spike, which often results when the hammer and valve spring tension is incorrect. This is the primary reason why I say that it is necessary to tune/adjust the hammer and valve spring in addition to adjusting the regulator. 

Quite simply, the spring rate of both the hammer and valve spring must be tuned/adjusted properly (with the valve spring tension to be as little as possible) while still being able to let the gun deliver consistent velocities during its regulated state and also when it comes into its unregulated state. Adding onto the increased number of shots from a well-tuned system, it is also the extra amount of shots yielded from the unregulated state that basically contributes to an even higher number of overall shots.
 
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That makes sense. 

The part I'm still unsure on is, when it falls off the reg, there isn't an immediate drop in power. At least, not a noticeable one. You could be shooting at 915 on the reg and still be above 900 for a number of shots off the reg. In this scenario, lowering the reg would give you more shots on the reg but at a lower power. 

If I follow what what you said correctly, you're saying that there is no way to get more shots on the reg at the same power but it can be tuned for more shots at a slightly lower (but still more than ample) power level. 

Would someone with an Impact be willing to conduct a short experiment in the name of Science? The experiment would be to shoot a string from a full charge, recording the speed and reg setting. When it falls off the reg, the reg setting would be lowered so it's back on the reg and the other power settings would then be increased to see if same or similar power can be achieved for additional regulated shots. 

 
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Hi

I m from Cyprus and i just bought the Vulcan 2 .177 because is the only size of pellet we allowed. Not higher. I had a diana 56 spring and i use to shoot the jsb exact heavy 10.34gr with grade results. I like long range shooting like 70m-80m. Now with my new rifle and after a lot of reading i want to try the H&N 21gr piledrivers at 850-900fps. Is this possible? I m planning to order the huma regulator and what is the prefer pressure to adjust it for my preference? Thanks
 
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