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DIY About PCPs and Tuning: Part One

About PCPs and Tuning: Part One

Today reader Hank whose blog name is Vana2 tells us about precharged pneumatics (PCP) and his experiences with tuning them. This is a two-parter, so sit back and enjoy. I was glad to see this report because my next job after testing the accuracy of the .177-caliber AirVenturi Avenge-X on high power is to tune it for improved performance.

If you’d like to write a guest post for this blog, please email me at blogger@pyramydair.com.

Take it away, Hank

About PCPs and Tuning: Part One
by Hank Vana2

This report covers:

  • PCP basics
  • The types of PCPs
  • PCP designs
  • PCP adjustment options
  • How PCPs work
  • Unregulated PCP power
  • Regulated PCP power
  • Summary

tuning pcp Girardoni
The precharged pneumatic (PCP) that started it all — the Girardoni repeating air rifle of 1780.

There are several different types of airgun powerplants — CO2, spring-piston guns, single stroke pneumatics (SSP), multi-pump pneumatics (MPP) and precharged pneumatics (PCP). I thought it would beneficial to do a deep dive into the workings of a PCP because their ease of use (no cocking or pumping) makes them popular with a lot of people getting into airgunning.

Attractive as “no effort shooting” is, the energy has to come from somewhere so I have to point out that a source of high pressure air (HPA) is needed. The additional cost of a HPA tank and filling it or a compressor has to be considered. To my mind, the support equipment is a one-time purchase that can be used with multiple PCPs and investing in a compressor for family use or sharing one with a couple of friends is not a deal-breaker — especially with the prices coming down as they have been.

PCPs shoot well right out of the box but fine tuning can improve the precision and increase their effective range. A factory tuned PCP that shoots 3/8 inch groups at 25 yards might be tuned to shoot the same sized group at 40 or 50 yards. Tuning also allows the owner to change the power to suit different applications — low power for indoor or backyard ranges, mid-power for general use and high power for hunting.

This report is intended as general information for people curious about PCPs and how they work rather than a definitive “how to” tuning guide. As I’m primarily talking to people who may not be familiar with this type of airgun, I’ll take some license with my explanations and minimize the technical stuff.

PCP basics

PCP two modern PCPs
Two modern PCPs with a configuration similar to the Girardoni.

The types of PCPs

I will address two types of PCPs. Those that are unregulated work with variable pressure air and the ones that are regulated work with a constant pressure.

Originally, PCPs consisted (schematically) of an air source and a valve with the valve managing the full pressure in the air reservoir. In more recent years many PCPs feature a regulator installed between the reservoir and the valve that serves to manage the stored air pressure, reducing it to a lower, constant pressure that’s more efficiently used by the valve.

A regulator controls the power of the PCP, allows for a greater useful shot-count and more consistent velocities. It also frees the shooter from having to manage the fill pressures. You just fill to maximum, shoot to minimum and repeat as necessary. Regulators do add cost and complexity to the airgun design and can fail or leak — but they are convenient. I guess the same can be said for automatic transmissions on cars.

PCP designs

A precharged pneumatic (PCP) airgun is one that can be shot multiple times without refilling, by using an on-board high pressure reservoir as a source of air. 

Whatever your preference is, you can find a PCP that you will like. There are purpose built PCPs for disciplines like 10 meter target, benchrest, field target and precision rifle shooting (PRS) competitions and many for general shooting and hunting. PCPs are available with bolt actions, side levers, semi-automatic and even full automatic actions. They also come in compact, bullpup, carbine, and regular (full-sized) configurations. Military, traditional and futuristic styles are all available in power levels suitable for all shooting activities including hunting anything from mice to moose. 

The components inside a low power target PCP and a high power big bore are similar. By changing things like caliber, working pressure, air capacity and valve design the performance can be tailored to suit a specific application or be generic enough to be adjustable to a variety of uses. Calibers range from .177 to over .500, with .22 and .25 being very popular.

Most PCPs on the market are designed to shoot diabolo pellets but many are now being made specifically to shoot slugs. The main difference between the two is in the barrel rifling and slug-guns tend to be more powerful. Many companies offer PCPs that can be used for both projectiles (diabolos and slugs) and have kits tailored to allow switching to different calibers and applications.

In the airgun industry there are no standards that must be followed, so barrel and projectile design is totally up to the manufacturer. For example, FX offers barrels for pellets or for slugs.

With a fixed power airgun it’s important that you purchase the correct one for the application because your options are limited to finding a projectile that works with the factory tune.

Most adjustable PCPs can (within their capability) be tuned to shoot a variety of suitable projectiles well. Some designs have a wide power range of adjustment and others are, through necessity, designed to a particular task. A lot is possible with tuning but be one should be realistic with their expectations.

PCP adjustment options 

PCP power adjustments
1. Transfer Port Aperture; 2. Hammer Spring Tension; 3. Hammer Spring Preload; 4. Valve Dwell; 5. Regulator Pressure

PCPs can feature a variety of adjustments; the regulator pressure and the hammer spring tension are the important ones. I’ll be focusing on hammer spring tension and regulators as these are common to most adjustable PCPs. 

Build a Custom Airgun

How PCPs work

To shoot accurately the PCP must meter out a consistent volume and pressure of air from the on-board reservoir. Some PCPs are setup at the factory to shoot at a specific power level, others are user adjustable.

A pneumatic gun uses air from a high-pressure source to shoot a projectile. In a PCP the air is held back by the valve until the trigger releases a spring driven weight (the “hammer”) to momentarily knock the valve open. The valve releases a measured pulse of air and then closes to reserve air for the next shot.

The volume of the reservoir is constant so the air pressure inside drops with each shot taken. In an unregulated PCP the valve has to deal with this variance, where the valve in a regulated PCP has an easier job as the regulator keeps the working pressure constant.

Unregulated PCP power

PCP unregulated power curve
This is a graphic representation of how the valve works with the reservoir pressure.

With an unregulated PCP, the valve is held closed by the pressure stored in reservoir. When the reservoir pressure is high, the hammer strike has difficulty opening the valve and only a small amount of air is released resulting in a low pellet velocity. As more shots are taken, the pressure in the reservoir decreases, more air can escape through the valve during the hammer strike and the pellet velocity increases. With each shot, the pressures drops allowing the valve to remain open longer (valve dwell) but with less power so, for a number of shots, the lower pressure but longer dwell balances out giving a consistent velocity. This is the flat part of the power curve. As the pressure drops the balance is lost and the velocity drops to below the useful range.

This cycle – too much pressure, optimum pressure and too little pressure – if plotted on a curve (see above), would show the velocity increasing, stabilizing then falling. At the extremes, excessive pressure can result in “valve lock” where the hammer strike is not strong enough to open the valve and at the opposite end, too low a pressure in the reservoir may result in the valve not closing releasing all the air in the reservoir. 

The trick with unregulated PCPs is to learn the range of pressures for the flat portion of the power curve and work within this range. Fill to the best working pressure and know how many shots are available before the velocity drops too low.

Regulated PCP power

With a regulated PCP the air pressure from the reservoir is reduced to the working level by the regulator and stored in the plenum (an area in between the valve and the reservoir). The valve works with the consistent volume and pressure of air stored in the plenum — eliminating the power curve. The shot velocity remains quite consistent from the maximum fill pressure until the reservoir pressure drops below the pressure set on the regulator. After that, the shot velocity is determined by the remaining power available in the reservoir – the same as with an unregulated PCP.


In this guest blog, I’ve documented answers to questions that have come up in airgun discussions I’ve had with people curious about PCPs. My intent here was to give a view of PCPs in general, what is on the market and a basic understanding of how they work. 

I hope I’ve achieved that, answered most questions and peeked a bit of interest. In Part 2 I’ll talk about tuning PCPs to get the most out of them.



72 thoughts on “About PCPs and Tuning: Part One”

  1. Hank,
    Nicely done; even someone like me, who is PCP-challenged, can understand all you’ve said here. 😉
    I look forward to part 2.
    Blessings and good shooting to you,

    • Siraniko,

      You’re right, there’s a lot more that can be said about PCPs – easily a whole books’ worth with a chapter for each discipline… I’m not going to go there 🙂


  2. Hank,

    Mission accomplished!

    In the second paragraph you say, ” (no cocking or pumping) “.
    Well you still have to cock the gun to load the next pellet/slug in the magazine.


        • Yogi,

          What you think should be properly refered to as semi automatic in rifles and automatic in pistols.
          Manual Loaders vs Autoloaders are what we are talking about when speaking about how cocking works.
          The difference between semiautomatic rifles and automatic pistols and Machine guns/pistols is not needing to pull the trigger repeatedly to launch the projectile.

          Don’t feel alone Yogi, it is a confused area, because folks are sloppy in the use of proper terminology.


          • shootski,

            You are right, I thought about that just after I posted. I believe that the only automatic airgun is a CO2 BB gun that is full auto.
            For PCP’s you still need to move a lever to advance the magazine. If that is not called “cocking the gun”, then what should it be called?


            • Yogi,

              There are semiautomatic and full automatic PCPs available. This one is from Hatsan…

              *** The Blitz is a full-auto, pre-charged pneumatic (PCP) air rifle. The Blitz is a select fire, SEMI/FULLY AUTOMATIC PCP air rifle! Available in .22 caliber, .25 caliber, or .30 caliber that can produce up to 53 FPE and firing up to 1,150 FPS.***

              Not my kinda airgun!

              Per Wikipedia, cocking a gun to load it is also called “charging it”.



    • Yogi,


      To play along 😉 and for the benefit of those who have never used a PCP, I’ll mention that cocking the PCP opens the chamber for loading the projectile and compresses the hammer spring.

      The effort/force to operate a typical side-lever is very light (a couple of onces), smooth and can be done with the finger tips or a flick of the wrist.

      The bolt action on my Maximus lacks the mechanical advantage of the lever and is stiffer.

      As a point of reference, the cocking force required for a PCP is less than that required to disengage the detent on a break barrel airgun.

      I missed mentioning anything about most PCPs being magazine fed repeaters and how they are loaded. Magazines could be a blog (and a rant 😉 ) all by themselves!


  3. Well done, thanks! I now have a better understanding of how these guns work. Especially the over-pressurization issues with an unregulated gun. Before reading this, I wasn’t clear on how over-pressurization could result in lower velocity. But now it makes sense to me.

    One question that lurks in the back of my mind: I have read that tanks such as those used for SCUBA are required to be tested (hydrostatically) and certified every so often before they are supposed to be filled with high pressure gases. This is for safety reasons. But what about the tanks and reservoirs built into PCP guns? Are they certified and deemed safe to use for eternity?

    • Elmer,

      If the outside diameter of the reservoir tube is under 2 inches, no hydrostatic test is mandated in the United States. Each county has different laws about pressure vessels.


      • As a former volunteer fire fighter who has more than a passing familiarity with Scott Air Packs, I can attest to the requirement to have the air bottles regularly scheduled for hydrotesting.

        The standard is that an air reservoir under two inches does not need periodic testing? At what point, however, does sense over-rule the rule. That is, if I had a few thousand pounds of air pressure near my face in a vessel that could, potentially, do an impression of a grenade, I think I would want my bottles tested anyway. I mean, what is a face or a collection of limbs or other body parts worth?

        I’ll stick to my springers, thank you very much. They aren’t as sexy as the PCPs and are fading back in comparison with them, but they just seem to work – well, until they break which happens, but all that is contained IN the air arm chassis.

        I’m not knocking the PCPs, BTW. If I were a hunter, I’d probably have the full kit and a bigger arms locker. But, we don’t have any noticeable feral hogs running around here on the North Coast of Ohio. At worst, in terms of pests, are occasional racoons and some mangy old coyotes from time to time.

        • LFrank,

          You are totally correct about pressure vessel safety.
          But i think the rules governing the 2″ and under vessels in the USA as well as other countries that adopted them is based on some logic.
          With airguns the problem comes in the small producers of custom airguns some of whom do not research or properly test their products. Unfortunately this sets up the buyer be ware scenarios.
          I do have one question for you. Are you just as worried when you get in a vehicle with airbags?
          The track record of airbags is significantly worse than PCPs.


          • Shootski,

            Frequently countries other than US will take the DOT and other US only requirements and re-write them into metric units and their manufacturing processes. I believe the EU requirement are 50 mm OD and 600 mm length which are slightly less than the 2 inches and 24 inches of DOT. Since I retired, I no longer have direct access to specifications and rules and must infer from what others post.


          • Shootski: I am aware of the dangers of the air bags, particularly if people do stupid things – like putting their feet on the dashboard or not using their belt restraints or any of the other things people to do make the airbag a lethal device. I think that the model here is discontinuous. in that the vehicle air bag is an explosive device, and purposefully so to obtain the speed of expansion necessary to provide a cushion in an impact. Any time one is exposed to an explosive device, no matter how benignly intended, it is going to have the potential for harm. A few grams too much explosive and the dynamics charge markedly. A mistimed let off and a loss of control crash is likely.

            The reason that the comparison isn’t entirely apt is that the air vessel is not MEANT TO EXPLODE whereas the air bag is.

            The whole thing is a risk/benefit trade off. As one who has responded, in the past, to a goodly number of horrific vehicle crashes, the potential cushioning of the air bag has to be evaluated, even the risk of a non-crash activation, against the consequences of no air bag in an actual collision. When people eat windshields or dashboards or fly out of the vehicle, very BAD things happen. Indeed, the worst outcome may be to survive for the helicopter ride to the level one trauma center; one’s not likely to be quite “right” after that whole experience.

            Most of my fire service experience existed prior to the pretty much wholesale installation of air bags in passenger vehicles and it was pretty gross at times and often terminal to those involved or producing catastrophic injuries. The tradeoff seems to favor the air bag systems despite the fact that NOTHING IS EVER COMPLETELY PERFECT. One has to accept that there are real world risk components to everything in life.

            I carry large CO2 canisters in my bike under seat bags on my bicycles for tire inflation out in the field. On a hot day in August, in a black nylon under seat bag, those cylinders ramp up their internal pressure. I accept the risk and use the system for a number of reasons despite knowing that I’ve got 800 psi charged steel cylinders under my derriere. In terms of the real risks, it’s more likely to be injured at trail and roadway intersections than the bike bag being the source of a major “ass-plosion!”

            We have to remember, on this side of the Final Judgement and the arrival of the New Creation, living squarely in this one, NOTHING IS PERFECT AND EVERYTHING HAS ASSOCIATED RISKS. I wore Scott Air Packs into burning structures in my time on the fire department, PCP users manage highly pressurized vessels on their air arms. We trust that our equipment is able to deal with the physical processes in volved, and we have to do the maintenance with the due diligence to mitigate harm and injury to self and others.

            • LFranke,

              “…we have to do the maintenance with the due diligence to mitigate harm and injury to self and others.“
              Yes and educate those we can to the need.

              I had an Alfa with bucket seats, headrests, roll bar and five point harness back in 1966; i had a father refuse to allow his daughter to ride in my car but offer to drive us in his car with raty lapbelts. I refused him and called a cab.
              I still think airbags are a joke when compared to a properly functioning harness.


      • There is another caveat: it must be seamless steel. So the exception for testing and inspection is for seamless steel cylinders that are 2 inches or less outer diameter and total length less than 24 inches. The aluminum and carbon fiber cylinders / tanks required periodic inspection and tests in order to comply with the DOT requirements. CO2 cylinders have their own set of rules / requirements under CGA but are very similar to DOT.
        The current maximum life of a composite cylinder is 15 years, but the Navy is working on getting that extended. I believe ( I do not know ) that the extension will apply ONLY to the Navy composite cylinders primarily because of the Navy’s inspection program which far exceeds DOT requirements.


  4. Hank

    Excellent writing. If you are inclined to start a successful business, become a consultant teaching companies how to write user manuals. That market extends way beyond the airgun manufacturers and the need is rather pressing.


    • Deck,

      No thanks, I’m happily retired 😉

      Done consulting, training, procedures and process flow as part of my job as well as several years formal teaching at a college level. Guess that shows through in some of my comments eh!

      My habit of making notes and flow diagrams as always been worth the effort. In one company, my manager came to me in a panic that he had just been told that we had 6 months to document our process for ISO compliance… 15 minutes later I dropped a pile of paper on his desk and we were ready for the auditors (got a big bonus for that).


      • Hank

        Another thanks for your pellet holder board tip. Very convenient and saves fumbling time loading pellets. I have 25 holes for .177 and .22 and 25 more for .25 pellets. I chose a 1 1/2” x 6” x 20” board. It’s heavy enough to stay put on the deck railing.


  5. Hank,

    You have done a superb job with this! You have answered many of the questions concerning the basics of PCPs. I am so looking forward to part two. BB is so mean. Now we have to wait on his publication schedule to read what else you have written on this subject.

    WARNING! – Newbies to PCPs should not read any further! It will only confuse you!

    I and other experienced PCPers know your subject concerns the operation of “modern” PCPs. The knock open valve design has become an industry standard in the manufacture of PCPs. You, I and others know that the early PCPs, including the Girdandoni, used a “timed” valve in which the valve his held open by the firing mechanism for a certain length of time. This allowed a “volume” of air at what we today would consider very low pressures to escape the reservoir and “slowly” accelerate the projectile down a long barrel until it achieved a useable speed.

    For a very, very brief period of time a couple of modern “boutique” airgun manufacturers offered this type of air rifle. It is a lot of work to get it right. Do I drool to own one? You can bet your bottom dollar on it. BB used to own one of them. I do happen to know where it is. Now if I can just talk the present owner out of letting me have it at something of a reasonable price. 😉

  6. BB,

    Superb article for a Friday! You done good! Most especially since you are publishing this before you attempt to tune the Avenge-X. There is just one problem though. We have to wait until at least Monday before we can read part two! You are so mean sometimes!

  7. I sometimes leave a tab open to this page, and read the daily blog. Today is the second time I’ve typed in a comment, hit enter, and get the response “you must be logged in”, and lost those words, although it appears I am signed in when beginning. Seems that after some time limit, you are logged out, with no indication on the open page. I’ll try again.

    • FM found out the hard way about that annoying glitch a while back; suggest you copy your comment before punching the “Post Comment” button, more so if the comment is “longish.”

      • Yes, I call it a glitch, as even if you are not logged in (vs. being mislead to thing you are), it should not simply take you to a new page and dump the posting. Hitting back does not retrieve it, either.

  8. Hank, good information.
    I have explained PCP’s to many friends and acquaintances. In doing so, I always point out the advantage that the PCP does not have a powerful spring slamming a piston during the shot cycle – as the pellet begins to travel down the barrel. The PCP pops a small valve that releases the stored energy of the already compressed air in the gun’s tube or bottle. Thus, a PCP is easier to shoot, and inherently more accurate. It will also produce less shock to the scope, which can often destroy a scope on a spring gun.

  9. Very informative; FM would encourage the experts who gather here to share more of their technical expertise on all classes of airguns for the enlightenment of those less enlightened in these matters, such as FM. Also, this would give Tom a bloggin’ break here and there.

    RR, not to put you on the spot but how about writing up how you customized that Maximus happily residing in Casa FM? Well, whenever you find your Round Toit.

    • Vana2,

      Nice Part 1. BZ will await next part.

      Hank I can not wait until they get to read Part 2!

      For the Readership:
      take it from shootski…DO NOT miss Part 2!
      Even Yogi!


  10. I know that no one here really cares but, today I picked up a Crosman 150 at the post office! Not only that, but it has laminated wood grips! Just to top it off, I am going to reseal it, test the velocity and see what kind of accuracy it has and share it all with you!

    Hold the applause! Just throw money!


      • Hank,

        Oh yes! I have to watch it though. One of the conditions of my getting this 150 is that I do a blog on resealing, velocity and accuracy of it. I woke up this morning and had the idea that I would write about Quinn’s pistol also.

        To educate those of you who are more than a bit confused and for some reason follow my ramblings, Quinn is my Grandson’s (Blake) friend and has become my “adopted” Grandson.

        At the last North Carolina Airgun Show I gave Tony McDaniel (TMac’s Airgun Service) Quinn’s 150 to reseal. It belonged to his Grandfather.

        Well, long story short, it is sitting here at RRHFWA waiting to be returned to Quinn. I figured, what the hey, I will give everybody a sneak peek.

        • Yeah, it is totally satisfying! I try to find neglected ones and then resurrect them. I have done 10 or so and give them away as gifts to folks interested in shooting. I try to find them for about $50 or less, so I bide my time until the right deal comes by. I like the earlier versions with the hammer spring adjustment and the lever in the CO² cap. I can “tune” those a bit for efficiency and precision. I have one keeper that is particularly accurate with Meisterkugeln pellets that I shared with all of you on occasion. Here she is again:

          • RG,

            It sounds like you really caught the CO2 pistol bug from Ian. I am trying. I have a 2240, but I am really not that impressed with it.

            When I got my hands on Quinn’s 150 after it was resealed, I was bit. I really like the way that pistol is built. In truth, the 2240 is really not that much different. The main difference is that the 2240 and its derivatives use a breech block and the 150 has the breech built into the barrel. The 150 IMMHO is a more solid air pistol. Unless I am mistaken, these “old gals” seem to be made from a better grade of steel also.

            We will see how this goes.

  11. BB

    Off subject but it’s the weekend. Received dart bolts today. Being prone to try anything at least once I shot a .177 dart in my .22 Benjamin NP break barrel. I was hoping the loose fit would diminish velocity to make it dart friendly. Well it either was too hot or too cool because the dart bounced back to my feet. Thinking it may have hit a metal wire on the regulation dart board I shot another. Same result except the dart bounced to who knows where. Oh well the rifle did not detonate and I was wearing protection so no harm done.

    Upshot: Don’t try it!


    • Decksniper,

      Can you do a little more investigating please?
      Could the dart have hit the board side on?
      My guess is that shooting .177 bolt out of a .22 caliber rifled barrel would make it VERY unstable both inside the bore limits and once out of the muzzle. I’m basing that on my experience with very slightly undersized bullets out of firearms as well as Big Bore airguns.
      Maybe someone has more direct knowledge/experience.


      PS: did my weekly maintenance shooting with my two SIG ASP 20s. Thirty pellets each, Off Hand at thirty yards into 80mm Skippy Peanut Butter jar seals! I’ll post photos and data later this weekend.

    • Deck, re-reading B.B.’s blogs on darts, he said to turn the dartboard target around and shoot at the back (no wires). You may or may not have to paint a target on the back.

      Also, back up to give the darts a chance to stabilize in flight. I imagine that the gun is too powerful and the darts are tumbling.

      • Roamin

        Will do. Stay tuned.

        I owe you a velocity test on my AR2078A but it’s too cold for CO2. I have shot it at 55* Fah with good accuracy but we know velocity suffers.


        • Roamin and Shootski

          Dart experience continued: Today I began by shooting a dart bolt in a Tech Force m-8 in .177 caliber at 33 feet. I expected it to have way too much velocity and it did. Dart went nearly in the center of target (POA) but so deep the needle is still embedded leaving me holding the separated plastic skirt. Next up was my Benjamin 1377 multi pump pistol. Two pumps went too deep but one pump was just right. A 7 shot group at 33 feet measured 3 inches.

          I did shoot at the reverse side but didn’t see much chance of hitting the wires. I Don’t think darts are going to be my thing but will await more reports from BB.


  12. Hank, nice article. Thank you for the great info. In basic terms, how does a regulator work? How does it let just a bit of the pressure through and the hold back the rest?

    • Roamin

      I think of a regulator as being a second air reservoir inside the first. Pressure from the first (A) on the regulator valve keeps it closed as long as (A) pressure exceeds the regulator pressure. Only the air from second reservoir can reach the chamber when trigger releases the hammer spring.

      Someone who has actually been inside can confirm or correct my thinking.


      • Decksniper,

        “Single-stage regulators are ideal for applications where – there is minimal inlet pressure variation during the period of use, for gases with low cylinder pressures, or in applications where there is further pressure control downstream of the cylinder regulator.”
        For more in depth information
        https://store.mathesongas.com/single-stage-regulators/#:~:text=Single stage regulators should only,a nearly constant source pressure.

        There is much to be learned by the airgun industry about regulators. Some companies and owners are just getting educated that if the inlet pressure is not kept within a relatively narrow band the output pressure will be/become unstable. That is why multistage or multiple regulators are beginning to be seen in very high precision airguns. It is also the main reason why most Benchrest shooters use large cylinders and continuously tethered airguns.
        As Hank points out, very well, the regulator type typically found in PCPs is currently a spring (Bellville/or other spring type) and a shuttle valve that operates against upstream and downstream pressures.


    • Roamin,

      The regulator (reg) set point (reg spring tension) is a balance.

      On one side of the reg valve you have the reservoir pressure, on the other side there is a spring (multiple “Belleville washers” stacked up) that holds, with the assistance of the pressure that is present in the plenum, the reg valve closed.

      (The plenum is the “mini-reservoir” in between the reg valve and the main valve that releases air to the barrel)

      When the trigger is pressed, the hammer strikes the main valve, opening it momentarily, releasing the pressure to the barrel and lowering the pressure in the plenum; without the pressure in the plenum, the higher pressure in the reservoir over powers the regulator valve spring and starts filling the plenum. When the combined plenum pressure and the (adjustable) spring power match the reservoir pressure the air flow stops and the PCP is ready for the next shot.

      The valve and plenum geometries, settings and pressures determine how quickly the plenum is recharged. On my PCPs that have a reg pressure guage, you can see the “flick” ( < 1 sec) to a lower pressure then back to the set point pressure. Some PCPs can take longer – especially if they are not set up properly.

      Hope this helps.

  13. As shootski has pointed out, the newer (and far more expensive) PCPs have started to go to multistage or multiple regulators where the pressure is stepped down to the operating pressure. This makes for a much more precise and controlled output, which is a great aid in accuracy and can greatly increase usable shot count.

    I have a bit of a conundrum with all of this. When I was younger and helping my Dad reload, we were as consistent and precise as we could be to help ensure long range accuracy.

    But knowing your airgun (or firearm) is also to me a big part of it now. I enjoy learning the shot curve of a particular PCP. When I started learning about my first Talon SS, regulators for these things were almost nonexistent.

    My problem is I am not by nature a target shooter. I never was. I am a hunter. This raises the question of just how many shots do you need? Yes, sometimes you miss. Pooky. But even then, with small game many states have bag limits. OK. I do not need a gazillion shots.

    Now, when I go after bigger game, I do like to have three consistent shots. That allows for me to have a miss and then some. Take my word for it that handling more than one deer by yourself takes all of the fun out of it.

    Part of me almost wishes we had a feral hog problem around here. Almost. I will settle with punching big holes in paper.

    Fortunately, I guess, I have not had to hunt to feed me and my family for many, many years. I do not hunt for fun. I never have. I will just have to satisfy my shooting desires with paper, spinners and the occasional feral soda can.

        • RidgeRunner,

          From Virginia’s own:
          https://dwr.virginia.gov/wildlife/feral-hogs/hunting-faq/#:~:text=Right now%2C the feral hog,populations exist on private land
          DWR estimates 3,000 Feral pigs in Virginia…NC has 100,000…must be good border control? DWR blames hunters.
          “Feral hog hunting is what is feeding the growing feral hog problem, even if hunters have good intentions and desire to help control populations in the name of conservation. It is a supply and demand system. Interest in hog hunting creates more hogs. If nobody enjoyed hunting them, we wouldn’t have the growing problem we have today.”
          I call BS on most of what they claim.
          Why? There are an estimated 2.1 million free-roaming cats in Virginia, of which 1.2 million cats are unowned. Free-roaming cats are one of the most significant threats to wildlife, and they present
          numerous risks to public health. Free-roaming cats also are subject to numerous risks
          themselves, including high mortality rates, particularly for kittens.
          So are hunters also to blame for all the feral cats?
          In the Shenandoah a bunch of farms have gone broke in the past two downturns and rumors are around about what happened to their pigs once the new land owners found they owned pigs.
          IF it really is only 3,000 feral hog; with some drones, IR, and Night Vision that wouldn’t take long to end.

          Once we get Porky Pig lovers groups we will all be deep in feral hogs just like we are in feral cats!


          • Never has FM seen such bureaucratic idiothinking; following that derailed train-of-nonthinking to its illogical conclusion, we would have to believe the proliferation of iguanas and other invasive pests in S Florida is due solely to residents’ hunting/culling them critters. Guess the neighborhood shooters have gotten it backwards because we’ve made them pretty scarce around here.

            FM is more concerned about the growth/proliferation of feral dumbocrats!

    • RidgeRunner,

      I personally own only four regulators. Three are mounted on 3,000psi 22ci Hpa bottles for my .25 caliber eight shot that can deliver 60 to 110+FPE.
      The other regulator (very expensive) is unmounted and used with my two 100 cubic foot Carbon Fiber cylinders; it is used for benched bullet/rifle testing for my .25, .301, .410, .458, .575 caliber DAQ rifles and pistols.

      I actually own ZERO directly regulated rifles or pistols.

      I get at least two full power shots from any of the Quackenbush rifles or pistols and at least one closer range coup de grâce. For hunting as you said,
      “…learning the shot curve of a particular PCP.”
      I find it enjoyable as well and it is all you really need for hunting ethically with maximum accuracy and best energy levels.
      I remain open to regulators but until they outperform a well balanced valve on .25 caliber and Big Bores i will be on the sidelines with my money.


    • LOL!

      …think that was a Colorado low, talk to them about it! 😉

      We got a foot and a half of wet, heavy snow from that storm – instant winter for us.

      We’d been enjoying an extended fall – bare ground and temps around freezing until then.

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