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Air Guns Umarex ReadyAir portable compressor: Part 1

Umarex ReadyAir portable compressor: Part 1

by Tom Gaylord
Writing as B.B. Pelletier

Umarex ReadyAir portable compressor

This report covers:

  • The price
  • What about eBay compressors?
  • What is the ReadyAir?
  • Set but don’t forget
  • The noise
  • The connectors
  • The test
  • Maintenance
  • Summary

Today I start looking at the Umarex ReadyAir portable air compressor. When Umarex sent me their press release on the second of December, I asked specifically to be able to review a media sample. I did that for one simple reason — the price.

The price

Yes, it was the price that attracted me to the ReadyAir. At the SHOT Show last January they hoped it would retail for $500, which is a killer price. It’s gone up a little since then, but not that much. It’s now retailing at $550, but I see that Pyramyd AIR has already deflated that a bit.

Why am I so impressed by the price? Because if Umarex stands behind this compressor it should work as advertised. And today I’m going to tell you some nice things about the scheduled maintenance Umarex recommends that supports that notion.

Price has been a deterrent to a great many people who want to get into precharged airguns. They are stopped by the apparent lack of an affordable high-pressure air supply. The air rifles themselves have decreased in price over the past 15 years until now you can buy a rifle with a lot of desirable features for under $300 — the price-point PCP (PPP)! But, other than a high-pressure hand pump, there has not been a good way to get air into those rifles for less than an outlay of twice what the rifle costs.

Not everyone is willing or able to use a high-pressure hand pump. That’s what make an affordable small compressor so desirable.

What about eBay compressors?

Yes, there are cheaper high-pressure air compressors. You’ll find several on eBay for prices that seem impossibly cheap. Are they any good? I really don’t know because I haven’t tested any of them. Reader GunFun1 has had one or two and sometimes talks about them, and that is the limit of my exposure. People believe that if something sells for very cheap, the seller is forgoing all the expenses of a storefront, advertising and such. That’s true but it also means they can pull up their tent stakes at any time and leave you holding the now-expensive and non-functional bag.

The ReadyAir, in contrast, is backed by Umarex USA as well as by Pyramyd AIR, which means that parts and service should be available for a long time. Of course the ReadyAir is also made in China — as are most of the affordable air compressors for airguns these days. But when a company that has a reputation to protect gets into something like air compressors, they make certain there aren’t going to be any quality issues up front. And when there are, because stuff always happens, they are right there to resolve it with you! That and maintaining a strong support chain adds cost to the unit.

There are seals in a high-pressure compressor that the Chinese can put in but up to this point I don’t believe they have. Even Crosman and AirForce Airguns, who both developed small compressors, ran into this problem. A compressor is something you simply cannot beat down to a price and expect it to hold up.

What is the ReadyAir?

The ReadyAir is a portable high-pressure air compressor for filling airguns. It fills to pressures up to 4,500 psi, which makes it ideal for many PCPs that have come to the market with fill pressures above 3,000 psi

The ReadyAir is made to fill airguns — not larger air tanks. However, Umarex does give the times it takes to fill a 13 cubic-inch tank, such as found on the Gauntlet (0-3,000 psi in 7 minutes), a 17 cubic-inch tank like the one on the AirSaber (0-3,625 psi in 11 minutes) and a 32 cubic-inch tank like you find on the Umarex Hammer (0-4,500 psi in 27 minutes).

The ReadyAir is portable. It weighs 26.5 lbs. without the cables and hoses. A handle on top makes it easy to carry. It is an oilless compressor, which means the required maintenance is low, but heat is something to watch out for. So the compressor shuts off if the operating temperature is exceeded. It also has a 40-amp fuse to protect the internal circuitry.

The ReadyAir operates on either 110V household current or 12V car current. The company advises you to leave the car running when you fill that way. The compressor  is air-cooled, so there is no water to worry about. Louvers on all sides of the case allow for air circulation and Umarex advises to run the compressor in the shade if you’re outdoors. And leave some space around the unit if you’re running it indoors.

Set but don’t forget

The ReadyAir has a single control panel that shows and runs everything. It can be set to show English or Spanish. The temperature display can be set to Fahrenheit  or Celsius. And the air pressure can be shown in psi or bar. You can set the air pressure at which the pump stops pumping, which would normally be the max. fill pressure of the gun you’re filling. You can set the temperature at which the pump will cut off, which can be set as high as 160 degrees F, and no higher. At 87 degrees F the internal fan will start and it will run until the temperature drops below 87 degrees F. So when you finish filling a gun you can bleed the line and disconnect the gun but leave the fan running — i.e. don’t unplug the pump until the fan stops. If the ambient temperature is above 87 degrees, allow at least 15 minutes of cooling before you pull the plug.

ReadyAir display
The display with the compressor under no load.

Umarex says to stay by the compressor while it runs. That is, don’t set it and walk away. Since it is only filling airguns that shouldn’t take too much time, because we don’t shoot them down to empty. So, the times listed above will be less in the real world.

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The noise

The ReadyAir is not as quiet as other small compressors I have tested. But it’s quieter than a full-sized compressor that will fill a large tank. Under no load it registered 86.3 decibels on my sound meter. That’s too loud to have in the same room if you expect to converse, so I think the garage or utility room is the place to run it.

ReadyAir sound
The microphone was held 3 feet from the compressor for this reading (left number, only).

The connectors

The compressor comes with both a 110 volt house current cord and 12-volt cables for a car. There is also an air hose that terminates in a female Foster fitting.

ReadyAir connectors
All the cords, cables and hoses you need come with the compressor.

ReadyAir ports
All the connection ports and terminals are in the same place on the compressor.

The test

I will test the compressor both indoors and outside. I will time it filling an airgun of known size. But that’s as far as I can take it.

If you want to know how long it will hold up under such-and-such an ap-plication, I can’t tell you. For that you will have to watch the comments as they come in. And longevity is the true test of these smaller compressors.


The compressor comes with a replacement 40-amp fuse and it is recommended that you keep several around to use when required.

Every 20 hours of use it is recommended that you replace the high-pressure piston rings and seals. Umarex provides an excellent 22-minute video that shows how to do this. I recommend to everyone considering buying one of these ReadyAir compressors to watch the full video, because it shows you an in-depth look at what keeps the compressor operational.

It takes a long time to put 20 hours on this compressor. Remember, this compressor fills a typical air rifle in a few minutes. Many shooters will use it for a year or more before the first rebuild is required. The compressor comes with all parts necessary for one rebuild.

Every 20 hours it is also recommended that you replace the compressed activated charcoal filter. That is held in by one Allen bolt and is spring-loaded for easy removal. A replacement filter comes with the unit. This is covered in the manual.


The ReadyAir is the lowest-cost high-pressure air compressor on the US market that has factory support. Will it change the face of airgunning in this country? Probably not. But with the push the PPP gave in 2017, this is another big shove in the right direction!

author avatar
Tom Gaylord (B.B. Pelletier)
Tom Gaylord, also known as B.B. Pelletier, provides expert insights to airgunners all over the world on behalf of Pyramyd AIR. He has earned the title The Godfather of Airguns™ for his contributions to the industry, spending many years with AirForce Airguns and starting magazines dedicated to the sport such as Airgun Illustrated.

153 thoughts on “Umarex ReadyAir portable compressor: Part 1”

  1. BB
    Are you sure you got it “On the second ‘on’ December” I will read on and hope it is not way better than the Nomad II I have already.
    From what I remember reading oilless compressors should be reserved for low pressure items like an air brush paint gun. But if you make it sturdy and use it in short bursts like an airgun fill and rebuild it on schedule it’s probably worth it and better than a hand pump for sure.

  2. B.B.

    Can this compressor be used for anything else? With the right regulator, can if fill car tires, scuba tanks, drive a nail gun, etc…..
    Having a single compressor that can “do it all” would make it attractive for a home workshop. To many toys fills the garage to much…….


    • Yogi,

      I am not sure if it could even fill a car tire. Would my 4,500 psi Guppy fill tank, fill a tire at all? If so, how many times? Maybe someone could do some math on that? I think a lot of it comes down to volume,.. or lack of it.


        • BB,

          Well, I am not so sure that I answered it very well myself. We have some smart people here, so maybe they could run some numbers.

          I do remember we were talking (here on the blog) about small tanks inflating big things (like a big life raft) but I do not recall the details now. Of course, that is different than trying to fill a tire,.. or run an air tool,.. off of something like this compressor. Even some of the small shop compressors will (not) keep up with some air tool air usage. Stated as: X cubic feet of air per minute at 80 psi,.. or something to that effect. I remember that being a question when I got one for my Shoebox.


          • Chris and all,

            As much as one might want one compressor to do everything, this won’t cut it. Based on the fill times that BB listed, I calculate that this compressor is putting out under 0.25 cubic feet of air per minute – which is fine for the high pressures it is running at, but totally inadequate for use at lower pressures.

            Most air tools need over 3 cubic feet of air per minute at around 90 psi (some less, many much more – like impact wrenches). You could of course use it to fill tires, and you would not even need a regulator given how agonizingly slow it would fill, but you would have to wait a long time for it to fill.

            The bottom line is that this is a specific tool for a specific job, and I would not put the wear and tear on it for any purpose other than high pressure air. You could probably buy a used pancake shop compressor for probably not much more than a rebuild kit and filter for this compressor – I know that your question was geared toward saving space in your shop, but this is not the place to make that happen.

            Interestingly, I have used a Shoebox compressor for many years, and it was designed with this kind of dual purpose in mind, but from the other direction. It uses a shop compressor as the first stage of a total of three stages of high pressure compression (stages two and three are in the Shoebox). I have had a shop compressor for decades and will never be without one – they are a a fabulous tool. With access to the air after the first stage going into the Shoebox, most of us use a good sized desiccant filter on the input and thus have no moisture issues to deal with at all on the output. They are rock solid compressors – too bad that the company went under due to the price pressures from the e-bay Chinese compressors . . . .


            • Alan
              I had a Shoebox compressor. Had no problems with it. Mine was one of the first ones that went to belt drive instead of the chain drive they first used. My buddy still gas it and is working fine to this day.

              And everybody always asks that question if these compressors will fill a tire and such. Volume is another part ofthe problem. Now I will say my China compressor is super fast compared to the Shoebox compressor I had and my back up compressor that is 12volt. But still not enough air flow to do a tire.

              But then again. I never tried and probably never will.

        • BB: Maybe this old long “retired” volunteer firefighter and pumper operator can help? What applies to water also applies to air – they are both “fluids” that can be pumped.

          Fundamentally, the choice is always between pressure or volume for a given amount of power. One can either generate a lot of, in this case, air VOLUME at a low pressure (think of blowing up an air mattress) or one can generate a lot of pressure but little volume (think of an hydraulic jack). This applies to all compressors and pumps. The very high pressure PCP pump is no exception.

          So, could the PCP compressor fill a vehicle tire? Yes, but it would take a loooooong time. It could literally blow the tire up, too, as in burst it. It would likely run through several cycles of heating and shut down before the job was done. If the thermal protection failed it would burn up trying to do volume work. It is not designed for volume.

          Could my venerable Coleman garage compressor fill the PCP? No, it is strictly a volume compressor that tops out about 150 pounds – it could barely pump my Trek Domane Road Bicycle Tires to max. It can run my paint sprayer and BARELY services my common nail pneumatic driver when shooting 16 penny nails.

          So, without varying the horsepower put into a pump markedly, the compressor either gives volume at low pressure or low volume at high pressure. The little compressor is designed specifically to do one task – fill PCP on-board air reservoirs/tanks to very high pressures with little volume. If you want to blow up your vehicle tires, you would be better served to buy a garage tank compressor or a “pancake” compressor. Even a humble 12V portable tire compressor one keeps in the trunk would do better for tires!

          Hope this helps! The choice is what one wants (without HUGE increases in horsepower) either pressure or volume!

      • Chris,

        I forgot to answer your Guppy question. The average car tire has a volume of about 1.5 cubic feet, and filling it to a little over 30 psi (~2 bar) would take about 3-4 cubic feet of air (at atmospheric pressure) out of the Guppy tank, which holds 18 cubic feet of air at atmospheric pressure when full. So you could fill several car tires from a guppy tank. If done carefully (after fabricating the right fittings with appropriate safety venting system) you would not even need a regulator to do it, as the tire is of a high enough volume that you would be able to control the flow with the valve.

        Of course I think it better to do it with a regular air compressor . . .


        • Alan
          The Guppy is 118 cubic inches but Joe Brantcato says its 18 cubic feet. So not sure what is up with that.

          So maybe that Guppy bottle wont fill that many tires to 30 psi.

            • Chris
              I went to Joe Brancatos site and he says basically the same thing.

              118 cubic inches and 18 cubic feet.

              It doesn’t work out right though if you do volume on a converter when you plug the numbers in. Who knows.

              • GF1,

                Yea, not sure how that works or how they rate them on fill capacity or internal volume. I looked at several sites and they did not all agree/match and/or they only listed one or the other. Oh well, looks like Alan is right.


          • Gunfun1,

            Pressure vessels for air basically have two “volume” ratings – the physical volume of the tank (aka the “water” volume, since water is basically incompressible) and the capacity of air that they hold at their max rated pressure.

            I think the Guppy’s water volume is a bit higher (l think it was a little over 100 cubic inches), but they hold 18 cubic feet of atmospheric pressure air in them when full.

            This is where thinking of pressure in Bar is so much better than PSI – one bar is ~14.5 PSI (standard atmospheric air pressure) , and that makes it easy to think of the “amount” of air in pressurized things – like the tire example. If we inflate the tire to a little over 30 psi (or a little over 2 bar) then we have put a little over twice the original volume of air into the tire under pressure (of course it had the atmospheric pressure air in it to start with), and since the average tire is about 1.5 cubic foot of air volume (estimated by calculating it as a toroid) that means we need about 3-4 cubic feet of air to fill it, out of the Guppy’s 18 cubic feet when full. Simple math that way . . . .

            Oh, and the Guppy is full at 310 bar, or ~310 times (air is not an ideal gas above ~3000 psi, so it is not linear at the higher pressures) the ~100 cubic inches = ~31000 cubic inches = ~18 cubic feet.

            As a side note, I sure wish we would have gone to the metric/SI system of measurement back in the 70’s when we had the chance . . . we are the only major country that still uses the dumb system we do today (the only other countries are Liberia and Mynamar, with Britain stuck in a “mixed” use state). Life would be simpler now, and less expensive too due to global standardization. But I digress . . . .


              • I think the thing that is throwing you off is that the 31000 cubic inches and 18 cubic feet are both referring to uncompressed air, not the volume of compressed air (note there are 1728 cubic inches in a cubic foot).

                The tank is only the 118 cubic inches in volume, but when full (meaning at 4500 psi) there will be about 31000 cubic inches of air squeezed into it, all taking up just 118 cubic inches of space.

                Looked at another way, your Guppy will actually weigh over a pound and quarter more when full than when empty – that is how much air we are cramming into it when we fill it!

                You have to remember that air is a compressible fluid, and water is not. Up to about 200 bar (~3000 psi) air acts as an ideal gas, and the pressure goes up by 1 bar (~14.5 psi) every time we add the original volume of air into the vessel (in this case, 118 cubic inches) – above 200 bar we need to calculate it differently as it no longer acts as an ideal gas, but to keep is simple it is non-linear at that point – pressure goes up more per unit added, but not massively so.

                If we were filling it with water and tried to force more than the 118 cubic inches in it, the pressure would rise so rapidly that the tank would burst before we even got maybe another 10 cubic inches in it.

                Hope that helps without being too technical 😉


    • Serious off-roaders (Jeep guys) have been using air impact and inflation tools for years. My last Jeep had onboard compressor made from an air conditioning pump, a storage tank of three gallons, and air hose fittings at all four corners of the truck. It could produce 300 psi. My newer Jeeps use scuba tanks to replace all of that engine bay stuff. Nowadays, the guys who can afford a $75,000.00 (!) jeep just go get CO2 tanks filled. Here is a link to one of the guys who sells the CO2 stuff. https://powertank.com/ It has lists of expected usage to be taken with a grain of salt.
      I have aired up all four tires, changed a flat with an air wrench, and loaned out air tools and tank to broken Jeepers on the trail. I use my shoebox to top off before every trip. OH! Almost forgot. The massive air horn in a tiny Jeep is a REAL attention getter. That is getting moved over to my new project, a 1964 Jeep FC 150 getting a Kubota 2.4 liter turbo diesel!

  3. B.B.,

    I hate to have to do this, but . . .

    “It . . .means they can pull up their tent stakes at any time and leave you holding the now-expensive and non-functional bag.”

    Holding an INEXPENSIVE non-functional bag. Today, sadly, air compressors are like hamburger wrappers. Toss ’em and buy another..

    “The ReadyAir, in contrast, is backed by Umarex USA as well as by Pyramyd AIR, which means that parts and service should be available for a long time. . . .when a company that has a reputation to protect.”

    If Pyramyd AIR would take the ReadyAir in to service it for free under a retailer warranty, that would be a different matter, but Umarex USA failed to honor the warranty against factory defects ro me, the original buyer from an Umarex dealer (not P.A., but very well-known) with my Walther LGV, which shoots with more buzz and vibration than a heroin addict in withdrawal.

    The note accompanying my unrepaired air rifle says the following:

    “Gun is a 21 Joule [15.48 foot-pounds] model shooting 1200 fps.. It is going to vibrate.” If they had chronied it like I have, they’d find it shoots a 7 grain Hobby about 2/3 of that velocity. And cheap big-box store air rifles that are medium powered vibrate. Expensive German ones like a Walther LGV are not supposed to vibrate. As many (but by no means all) LGVs from this era shoot smoothly. If they had shot it (they provided no numbers for my LGVs performance, so I can only conclude they did not even shoot it once) they would have immediately heard it honk loudly like a Canada Goose and determined it was defective.

    Umarex USA concluded their short note assuring me that the only way to make the LGV shoot smoothly was to reduce its power “down to 16 joule or 7.5 joule.” B.B., Did you know that about air rifles?

    I opted to have them return the LGV to me.

    A warning to all of the readers of this report: Buy a ReadyAir for a lot more money than an annonymous brand off of an auction site, and will UmarexUSA honor their warranty if it breaks down?


    • Michael,

      I have always been hesitant of buying Umarex. For one thing most everything with their name on it has no appeal to me. Now it sounds as if their absorption of other name brands is causing serious issues. Likely the same thing that happened to Webley when it had Hatsan build its airguns, is happening to Walther and other brands. To meet the required price point, products are made more cheaply. Cutting corners becomes a necessity. Some products are even made in China and rebranded.

      As for not honoring the warranty, A pox on them.

      • RidgeRunner,

        Ever since I first shot this Walther (shoot it at tin cans, not shoot the Walther with a second gun, although that is an idea), I have thought of the Walther brand as overpriced junk, poorly designed, badly manufactured, having mediocre Quality Control, nonexistent support and unjustified esteem. I think of Walther as the Ford Fiesta or Chevy Chevette of airgunning. That’s what they did to my concept of their brand.


          • BB,

            Good for you,.. if it works out. Honestly, I thought this was long ago resolved.

            The “honking like a goose” is quite puzzling though. I can not imagine what would be causing that.

            Air blowing past the piston might. Somewhere I recently read where someone had a springer and the compression chamber was not all one piece. The end was a fitted a cap/plug and the o-ring for that cap/plug was bad. An air leak there might make some odd sounds. I am not sure the LGV is even made that way though.

            Good luck figuring it out if it turns up on your doorstep.


          • BB,

            I would like to see that blog!

            A lot of times a poorly performing springer can really be improved with a bit of spit & polish (clean, deburr/polish, shim and lubricate). The level of “fit & finish” is a way to cut production costs and that is easily addressed by the owner.

            Turning an airgun “sows ear into a silk purse” is a fun project and with a bit of time often yields a smooth shooter with a good improvement in performance.

            I would like to see what tricks and tips you would use to fix Michaels rifle.


                  • B.B.,

                    The sound is not the cocking; it’s when he takes the shot. It’s actually exactly at 8:42 on my computer. It’s quite loud compared to the other audio in the video.

                    The pitch is A 440hz by the way. As a guitarist I decided years ago to memorize that pitch so I could tune a guitar without a pitch pipe just using that pitch in my head.


                    • Michael,

                      Okay, I gotcha. But I am wearing hearing aids and cannot fully hear the sound. I hear a hint of it and have not used headphones.

                      It think it’s still related to an under-lubed piston seal, but I will examine everything when I bust into the powerplant.


                    • Michael,

                      Yes I did. I was watching for that. Yours is a .177?,.. I forget. Maybe it is over sprung for a .177? Maybe you need to try a super heavy pellet for a .177?


                  • Chris, yes mine is in .177. Your idea about it not liking light pellets occurred to me, but I can’t remember what I discovered. I don’t recognize the pellets he says he uses, they might be Australian. But the names sound like lightweight match wadcutters.

                    Thing is, it’s not a magnum springer. It shoots at about 14 or 15 fps.

                    Nevertheless, you might be onto something.


        • Michael,

          Have you seen other videos/reviews of .177’s that do (not) show that sound?,…. thus leading to the conclusion that something unique to yours might be going on? Then again,.. there is at least one other one,.. the one in the video you linked.

          Ok, not rated “magnum”. It is still not uncommon to have too much/wasted spring leading to other issues like twang and vibration. GF1 did a TX200 and cut it to 1/2″ of free play and lost no fps. I do not imagine that they spend too much time getting the “perfect” spring when they make these.

          There might be spring kits for this as well,.. like a Vortek kit or something.


        • Michael,

          I am really sad to hear that as I have been seriously thinking of the Reign. Finally, here was a decent ‘pup at a decent price.

          I will have to wait and see what you and BB work up.

            • Chris
              That LGU was a smooth shooter plus it had that nice wood stock.

              You can’t find one with a woodstock now.

              They are synthetic stocks now on the LGU plus they uped the power. So they might of messed up on that point too.

              They should of left it alone. In my opinion I think that they would be selling more now days.

              Maybe they will bring back the woodstock and original tune one day again. I will get one again for sure if they do.

              • GF1,

                I think the plastic stock is maybe 10% of the problem. It amplifies the honk. Of course if there were no honk, then there would be no sound to amplify!

                I have a plastic Gamo Recon ($79, IIRC) that has a mediocre trigger, isn’t particularly accurate, but shoots smoother than my LGV.


  4. BB,

    Looking good. I always like seeing progress. Having the Shoebox, I have not looked into other compressors. Mine came with 6 rebuild kits and the estimated time to a rebuild is like 80-90 hours. I keep a log and am at around 31 hours. Keep a log! If it takes 10 minutes to go from 3000 to 4000 and 6 months dowen the road that same 3000 to 4000 fill takes 15 minutes,.. that will confirm that a rebuild is coming up.

    On other air gun sites, the cheap imports get talked about all the time. Even among the cheapies, there are ones to avoid. Some people tear then down right away and replace all of the O-rings with better ones. Others add cooling systems or augment the ones that came with it. Some add fans and/or remove the covers and use window fans to cool components. My general takeaway is to do your homework and also that it is a bit of “roll the dice” venture.

    That said, having Umerex and P.A. behind this makes it a no brainer. Looking forwards to more reports.


    • Chris,

      Just thought I’d share a data point. I have a Shoebox Max, and like you I log everything with it – that is a very good thing to do. I have a little over 200 hours on it now, and did my only rebuild on it at about 140 hours. It really did not need it, but since I (like you) was expecting to have to do it at under 100 hours, I just decided to go ahead and do it. Bottom line – no change in performance afterwards, so I have no idea how much longer it could have gone (the o-rings that came out looked so good that I kept them).

      I have always lubed it properly, and I added the auto lube kit at about 100 hours, and switched to Krytox as my lube after the rebuild, so these o-rings might make it to well over 200 hours of life on their own. The bottom line is that the o-rings last much longer if you have the polished compression rods than the original ones the Shoebox started with.

      I hope yours keeps running well for a long time!


      • Alan,

        Sounds good. I keep mine lubed as well. I bought a Shoebox Max and it came without the sticker on the front. (just “Shoebox”) I called and they said I had a Max and it must have been caught in the transition to the Max. They sent me the longer belt and a new pulley for free. I think the cylinders and tubing made some changes over the years,.. but at any rate, I had the latest. My rods look polished, so I assume that is what I have. I am still running the smaller pulley and belt and saving the larger set for back up. Heavy silicone on the wipers, white lithium on the rod guides and 5-30 Synthetic on the bearings and such.

        I also cycle it during the Ohio Winter and let it run for about a minute unloaded. Same for the California Air 5 gallon horizontal shop compressor. < is nice and quiet. Love it. Both are in the living room next to the TV and I do not even turn up the TV. The California Air had some of the quietest decibel ratings of any on the market. Motor in the middle and a cylinder on either end. The ad said that 2 cylinders allowed cooler running, or something to that effect.

        I also added an inline 8" or so water filter. 5 micron I think. Like you would see in a shop. I filled with desiccant beads. Works great and only needs beads swapped after about 5+ tank top offs. They change color,.. orange to green. That is ahead of the Shoebox. No filter after the Shoebox. Direct to tank at that point.

        Thank you for all of your input today and the sharing of knowledge! 🙂


        • Chris
          This is bringing back memories of when I was telling you about the system we had at work to dry the air.

          Back believe when youjustgot your Shoebox.

          So its been working for you.

          • GF1,

            Yes, it has done me just fine. Then again, I do not shoot like you do. If you recall, I took 50′ of hard wall flex tube (about 3/8″ OD) and put that in a bucket with water/ice packs for the initial tank fill. Looks like 2 hours and 33 minutes to fill the Guppy from zero to 4500 from records. I am sure I paused it for a half hour or so a couple of times, but that should be the total (run) time. The desiccant bead filter came later. Still the same set up, but no water/ice used.

            I am not sure I would like going directly to the gun.


  5. BB
    I do still have my China compressors. Well I have one and the other is out at my brother’s. Which we did use the other day. I brought my SAMarauder out because he wanted to try it out. Said it reminded him of when we was kids shooting our semi auto. 22 rimfire guns. He’s getting one.

    Anyway back to the compressor your testing. I have a good feeling it has the powerplant like one of the other compressors I got as a back up since my brother has my other compressor and I don’t have a hand pump anymore.

    It fills with about the same speed as the compressor your testing. It’s a no name brand of the Hatsan Spark I believe it’s called or the Crosman traveler. Mine is small and only weighs around 12 pounds and has two high speed cooling fans similar to a computer desktop cooling fan. Its oil less and uses no water for cooling and it runs on 110 volt with the included converter or 12 volt. Which is another reason I got it as a back up. I can still fill my guns if the electric goes out. It will fill my Gauntlet in about 3-1/2 minutes which is way slower than my China compressor which will fill the Gauntlet in about 1-1/2 minutes. But if there is no electric my China compressor won’t fill anything.

    But the compressor I have has a round cylinder about 2-1/2 inches in diameter with steel blocks on each end. That assembly is probably about 8 inches long and is contained in the side of the sheet metal covering. And it’s about the size of a piece of standard copier paper and about 10 inches tall. That’s the outside dimensions of the compressor. It has built in carry handle too. Oh and its quiet too other than a small whine sound coming from the cooling fans.

    If the compressor BB is reporting on has the type of compressor inside as my 12 volt compressor I believe it will be a dependable compressor. That is one of the reasons I wanted the 12v compressor for my back up compressor. The type of compressor system it uses. And not that it matters but I got it on sale for $289 and free shipping.

    I think the compressor BB is reporting on should be a nice compressor. Would like to know more about what compression system it uses though.

    • GF1,

      Yes,… compression system,… what is yours? Most are 3 stage, are they not? My Shoebox is fed with a shop compressor and then has 2 cylinders inside (as you know).

      How do these small compressors achieve all 3 stages in one unit? Is there any with 2 stage only? Or,.. even 1 stage only?


      • Chris
        I’m not sure how many stages my 12v compressor is.

        Those 2 blocks on each end have a steel 1/8th inch diameter tube connecting them together. Then one block has steel line coming out of it that connects to a block that has the pressure gauge in it and the fill hose coming out of it with the Foster female quick disconnect fittng that you hook to your gun.

        So maybe a 2 stage system. ???

        • GF1,

          You lost me on all that. I do not have a clue. Is it piston type? Direct drive or gear or pulley drive?
          Is there some of these pumps that do not use pistons at all and use some other method?

          HAM showed a new booster pump awhile back. That is an example of using low(er) pressure to make a higher pressure. Is something like that being used in any of these new all-in-one pumps?


          • Chris
            There is a piston inside that goes back and forth. I’m guessing it compresses on both sides of the block. There is probably check valves in each block that build the pressure then sends the air to the block the gauge and fill hose is in.

            And yes it has a small motor with a exposed crankshaft that hooks to the piston rod coming out of one of the blocks. It’s a very simple set up.

            Picture the blocks on each end of the cylinder tube as the cylinder and head on a normall engine like a lawn mower engine.

        • I would say that almost all of the crop of lower priced compressors that have come out in the past several years are all two stage. The more expensive, higher capacity/capability compressors are almost all three stage and some are even four stage. The elimination of a stage of compression is part of how they reduce the cost of the units, but it comes at the cost of higher internal heat generation, limiting their operation. Note that all compressors use a metal tube between stages, and this tube is used to do two things – move the air from one stage to the other, and to allow some of the heat in it to be rejected via the cooling air flow over ir. More stages allow for less compression in each stage and more opportunities to vent the heat of compression out of the system to cool the air charge (increasing both system robustness and system efficiency).

          As for the discussion on Shoebox stages, it was specifically designed with the first stage of compression being done by the shop compressor. So the unit has two in it, but the system is truly a three stage compression system, with the fist 6-9 bar of compression (depending on the generation of unit and its input pressure) coming from the shop compressor. Yes, it can run without a shop compressor as an input, but it will take 6-9 times as long to fill that way as the air flow into it is reduced by that much.


          • Alan
            Yep that’s what I was telling Michael.

            So how many stages would you call my Benjamin hand pump that I boosted with my shop compressor. Which did make the pump fill a gun quicker.

            Would it now be considered a 4 stage compressor since I added air to the hand pump that would also function without the additional air?

            When I had my Shoebox compressor there was only 2 pistons that transferred air which I would call 2 stages. The shop compressor is just a supercharger if you will. It boosts the 2 stages that compress the air. The shop compressor is not a stage of compression. It just helps get the air to the compressing stages of the pump.

            • Gunfun1,

              I agree that when you boosted your 3 stage handpump that you were using 4 stages of compression when filling your gun. Note I said four stages of compression – meaning as a system; you were using two pumps together to get that four stages of compression.

              The same applies with the Shoebox – it is a two stage pump, but is was specifically designed to have the first stage of the Shoebox feed by another compressor, resulting in a three stage compression system.

              By contrast, if you try to feed 85 psi into one of the two stage compressors like this Umarex one here, they won’t even run. Even if the fuse does not blow, the motor almost certainly will not be able to turn the crank for one revolution.

              • Alan
                And ok I can see it being another operating stage to the function of the compressor. So why not call it a 3 or 4 stage compressor.

                And yep on thepumpsnot starting if you was to add air with the compressor BB misreporting on and the 12v compressor I have.

                Andthe chinacompressors won’t start either unless you haverhebleedvalve open first. So i know they wouldntcrank with additional air.

                Physics always wins if i can say it that way.

      • Chris,

        You feed your Shoebox with a shop compressor, do you not? Is yours really a three stage compressor? Lloyd Sikes has/had a couple of those Shoebox compressors. He incorporated additional input and output filtration on his.

        Mine is a three stage compressor, but it is only portable because I modified a lawn cart to carry it. Mine is also oil lubricated and water cooled.

        • RR,

          I would say the “system” is 3 stage as in there is 3 distinct levels of air being pushed. Not all in one unit, but yes I would consider it 3 stage.

          I am not sure, but I think the incoming air pressure can be boosted higher and maybe gain some benefit in reduced fill time. My shop compressor is set to 130 and only cuts on 1 or 2 times during a 25 minute tank top off and quickly shuts off (after the first fill). Maybe a minute run. I think it is 80 on the low side and 130 on the high, without checking. I have never messed with it.


        • RR,

          Yeah, our compressors are on the heavy side of “portable” (I added 4 inch casters to mine) but where they really stand apart from the smaller less expensive compressors is that they have no problem filling a large carbon fiber tank to 4500 psi.

          A 12v hpa compressor would be nice for a backup but I prefer my 80 pounder for home use.


        • Michael
          The shop compressor adds air to the first stage piston on the Shoebox compressor.

          The Shoebox will still build compression without the shop compressor attached. It will just biuld very slow. You can run your shop compressor for the Shoebox compressor at 85 to 100 psi. The Shoebox will then build pressure faster.

          Do you remember when I hooked my shop compressor to my hand pump to act as a booster to the hand pump. I guess I sort of turned it into a 4 stage compressor when I did that. ???

  6. I think this would be a good option for someone who doesn’t have a dive shop nearby. But since I have a dive shop nearby, an 80 ft.³ carbon tank would make more sense for me for about the same amount of money. I have a small house and no garage so really no place and room to put a noisy compressor.


  7. Chris, and anyone else who may be interested,

    Here is a picture of my shooting bench in progress. The frame came from a McDonald’s they were remodeling. My grandson and I had built the seat the other day. This day my buddy and I were getting ready to start on the top.

  8. Was going to post this yesterday but got occupied with the toothpick crossbow blog and trying to find one to order. Well and of course I was shooting yesterday too. Been off work since last Wednesday and been getting caught up onthe to do list.

    But maybe people would be interested in converting thier pcp guns that use a probe into a Foster fitting and an additional gauge or a plug on the opposite side. I chose a AirVenturi gauge that reads in psi. So now my gun has the original gauge that reads in bars and the one I added that reads in psi and the Foster fill fitting.

    The hole in the gun for the probe just happened to be the right size for the taps I used. The gauge took a 1/8″ NPT tap and the Foster fitting I used needed a 1/8″ BSPP tap. You will need to find a Foster fitting that has a set screw thats been drilled with a hole through the center of it to keep the the check valve from falling out and still let the air to pass through to fill the gun.

    Heres a picture of my (Hatsan at44 QE long pump action) air tube I done the mod to. So no more probe needed now.

  9. My brother and I split the cost of a Chinese compressor from AliExpress a couple of years back, and have used it just a few times. It works, but does require some tinkering. We got a filter cartridge and the media and dessicant for it, and it was not a trivial expense.

    Since then, my local volunteer FD have been friendly and kind enough to fill our tanks with dry breathable air, from their Scott setup. My tank has a hand tight fitting just like they use on their SCBA’s, and getting it connected and filled to 4,000 psi takes about 2-3 minutes from cascaded tanks they use.

    I worry about the moisture and lubricant that can come from any of these compressors (especially the oil lubricated ones) without proper filter/drying. In my career, getting clean and dry air to the automation required a lot of attention – with aftercoolers, refrigerated dryers, coalescing filters, etc., and getting contaminated air in the lines could be a major problem, and that concerns me with my PCP guns, as well.

    In getting any new compressor, I’d consider just how the air might be contaminated, and what filtration is there to deal with it.

    • Jerry
      We have alot of automation at work. We have 3 big compressors and each of those has thier own dryer system as well as a additional dryer before a big hold tank. Dry air is important to keep all the equipment functioning right.

      And what did the compressor look like that you got. And what kind of tinkering did you have to do?

      • It’s a “real” Yong Heng – 3 years old now. The “tinkering” was getting a better filter setup – the “Golden Al Tube” (the little filter cartridge that came with it we thought inadequate), loading it with the right media and dessicant (zeolite sewed into a sock), setting up the water cooling, figuring out how to startup and shutdown, drain the water out of the first stage during operation. It could fill a 1 hr SCBA tank from 2,800 to 4,500 psi in about 25 minutes. We have only used it about three sessions. My view of the Yong Heng is that it is workable, but not robust, especially for anyone who might expect “plug and play”. They will require some serious maintenance if used regularly.

        • Jerry
          That’s what my 2nd China compressor is. A “real” Yong Heng compressor. It does seem to be better quality and assembled better than my first one. It does seem to not heat up as much as my first one too.

          And I’m impressed. Only 25 minutes to fill the scuba tank. What size is the scuba tank? I was thinking about getting one of the 90 cubic inch Benjamin buddy bottles again but wasn’t sure how my Young Heng would work filling it. I only use it to fill guns right now.

          • The SCBA (note, SCUBA are underwater, lower pressure, larger and heavier, not very suitable for PCP use). SCBA take pressure to 4,500 psi, lighter and smaller, and are widely used by firemen. They rate them for minutes of air supply, which can be confusing as there are multiple parameters involved. So, using the 3M/Scott Fire & Safety specs, 30, 45, and 60 minute tanks are 218, 485, and 550 cubic inch (water volume) tanks. The tank I referred to was a 60 minute. I’d guess a 90 in3 tank (about 15 SCF 4,500 psi air) could be filled from 2,800 to 4,500 psi in about five minutes by a Yong Heng, and fill your airgun (215 cc vol tank) ten times.

            • Jerry C
              So just estimating. How long do you think it would take the Yong Heng compressor to fill a 90 cubic inch Benjamin buddy bottle?

              I would like to get one of the buddy bottles. I’m going to need one for when I take the Wingshot ll out in the woods shot shell shooting.

              If your not sure that’s ok. But would like to know.

                  • Seems like a good combination. The 90 in3 refers to 90 cubic inches. That would be the “water volume” of the the tank. Not to be confused with the air capacity, which is usually shown as SCF (standard cubic feet) of air at normal atmospheric pressure. The higher the pressure, the more SCF you get, of course. I feel sure you can fill your buddy bottle to >4,000 psi with the Yong Heng in well under 15 min, and refill your Wingshot about ten times with it.

                    • JerryC
                      Ok that’s good for me. My Shoebox would take around 50 minutes to fill my 90 cubic inch Benjamin buddy bottle I use to have from 2000 to 4500 psi.

                      If the Yong Heng will equal that I’ll be happy.

  10. BB, this compressor seems like it will be popular, but you should still get a small carbon buddy bottle. Having the bottle gives true portability. Michaels Walther should be a piece of cake. A Vortek kit cured my heroin addicted R10, but then I didn’t even know what a buzzy shooter was untill I did. 14 ft/lbs seems so easy now. But also, my 12 ft/lbs tuned Diana Bandit makes almost the same power for 11 shots.A nice tight e.s. The receiver comes drilled and tapped for the UTG dovetail to Picatiny adapters that screw down perfectly flat, something they could not do on the P1’s dovetails, making the compact red dot I got for it useless on that pistol.I always wondered what those little screws were for. I put the micro dot sight on the Bandit. I tried an MRS dot sight too. The dot sights make the Bandit wonderfully lightweight, but I get 1.5 inch groups at 18 yds, not two pellet diameterx3pellet diameter groups when it has the 2×7 variable long eye relief scope on it. The scope stays on it now. Now, if I could just fill it to 4500 psi.. Keep up the good work! Oh, I have 5 more years on my carbon 1hr bottle I got from Joe B.
    I need a proper bottle filler in the not too distant future.

  11. B.B. and esteemed Readership,

    As a Dark Side devoté i couldn’t help but try to be helpful after the massive exchange above on the topic of gas Volume vs. Pressure. I thought about dropping the Gas Laws and a few formulas; but the last time I did that it obviously didn’t stick.

    So I give you all the SECRET tool of an Old Hand from the DARK SIDE:

    With a very little work you will WOW everyone else and also yourselves.


    • Shootski,

      You are right,… I went to the page and went “WOW!”. Pondered it all a bit and closed the page.

      I guess it did not stick “last time”,… or this time. 😉 Thanks for putting it out there though. I am sure somebody smarter than me can make use of it.

      Chris 😉

          • Chris USA,

            I have tried to live my entire life like he recommends! It works and i proved it as a flight instructor. Made my teachers go nuts and my kid’s teachers hate me for suggestions i made on their teaching style!

            I guess i never got past the toddler stage? That must be why I still PLAY with BB guns!


            • Shootski,

              Nothing wrong with any of that,… not one bit. My brother is very much the same as the speaker,.. I suppose. Then again,.. he pretty much did it “right” all the way, where I on the other hand,………

              Thanks again,……. Chris

    • Shootski,

      That is a nice convenient tool, and I have bookmarked it for future use and convenience, but do be aware that it is all based on ideal gas laws. It will be very accurate for calculations up to about 3000 psi, but will be off by some as you go up from there.

      In short, an “ideal gas” is a hypothetical one in which the molecules in the gas neither take up any space (are treated as infinitely small) and don’t interact with each other (no electrical attraction or repulsion). Air does behave that way pretty well up to around 3000 psi, but after that the density of the air molecules get high enough that those effects begin to matter and things are no longer linear.


      • AlanMcD,

        How high can you pump?

        All my Big Bore operate at close to 3,500 psi.
        So far my work beyond that pressure plateau is theoretical and you are correct that things go very squirrely making Internal Balistics for airguns even more difficult to comprehend. I have a number of documents from various government Labs trying to determine how much velocity airguns are actually capable of attaining. The air in front of the projectile in the bore and the volume, temperature, and acceleration of the gas charge behind the Pellet are the real culprits we need to learn how to overcome in order to get significantly higher MVs efficiently.


        • Shootski,

          Give me enough dineros and the air in the front of the projectile in the barrel can be all but eliminated, especially in a lab. Now the variables come down to caliber, barrel length, projectile weight, pressure and then valve geometry and timing.

          Having ports in the barrel to add air as the projectile goes down the bore like a rail gun and a vacuum in front. I could beat any velocity yet attained. Lots of high tech timing and valve work. Maybe I could ask for a grant. What is the limit on pressure?


          • Don,

            “Gender studies” in some third world country is in the latest house bill. A few million? (B?) at least. I would say you have a pretty good chance at a grant! I say go for it! I will sign up to be your understudy. A paltry $500,000.00 will suffice for my compensation just fine!

            Chris 😉

          • Don,

            There are a lot of need ideas there – they would sure be fun to play with, but as you say, mucho dinereo to do so. I especially like the idea of the secondary (or more) ports in the barrel – that would help so much in dealing with accelerating the mass of the air (by reducing the mass to accelerate). Nice thinking!


        • Shootski,

          I fill my tanks to 4500 because it is a breeze to do with the Shoebox, but I don’t have any guns that I fill above 3,000 psi. I don’t have any big bores as I just don’t have the need, but someday I might try to get into small caliber slug shooting for the accuracy and ballistics challenges, so I have spent a little time thinking of what challenges lie in that space – and you are very right that things get different there.


        • Shootski
          You should see what pressure my Wingshot ll operates at now.

          And yep it still shoots the 210 grain Balle Blondeau .50 caliber at 650 fps.

          Now 2000 psi fills instead of 3000 psi.

            • Shootski
              I have shot a bunch of shot shells through it and I’m now getting 9 full power shots using the high power cocking position. Before only 5 shots.

              It was waisting so much air it wasn’t funny. All I did was cut some coils off till I seen the power drop about 25 or so fps. The gun now works from 2000 psi to 1100 psi. It reminds me of when I tune spring guns. The Wingshot ll striker spring had about 1-3/4 inches of preload. I ended up with about a 1/8″ of free play in the spring. Basically a 1/8″ of space between the spring and the striker.

              I do need to spend some more time shooting the Blondeau’s though. Its definitely a bad boy shooting those. It looks like someone took a 1 inch drill bit and drilled nice clean holes through two 2×4’s. And that was at 50 yards. And I did a shot into the ground with the muzzle about 2 feet away and shot one of the slugs. I stuck a stick in the hole it made. It went 9 inches deep in the ground and that was with the ground temperature around 32°. So yep its making power no doubt.

              And yes I’m very happy I got it. 🙂

  12. Shootski
    To me it looks like there are different people that came up with different formulas and they are all getting different results.

    Is that what you are trying to get across or am I looking at it in a different way?

    • Gunfun1,

      One law is volume stays the same, another is temperature stays the same, and the other is the pressure stays the same; all the other variables get to change. The others are fixes for all together and the k constant to hep confuse everything. The three basic laws are usually enough for airgunners.


        • Gunfun1,

          All the equations relate and work together as a common set of gas laws. What you are seeing is the different relationships within the laws that were discovered by different people over time, and these laws were named for them. They are not in contradiction, but show what happens under different conditions (for example, holding one variable like temperature / pressure / volume constant.


          • Alan
            I wonder if I should even be thinking about all this physics stuff.

            I’m thinking my compressors don’t even know the difference. They just keep doing what they do. 😉

            Thank goodness.

  13. OK Everybody!

    It seems there are more people interested in my shooting bench than I thought. I pretty much finished it today except I want to add a couple of braces to the wooden leg. I might add an arm rest later. We will see.

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