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Education / Training Buying a high-pressure air tank – Part 1

Buying a high-pressure air tank – Part 1

by B.B. Pelletier

This report is for Abe, but with the large number of folks coming into precharged airguns, I suspect many people need to read it.

When I started in precharged pneumatic guns (PCP) in 1996, the need for air was not as critical as it is today. The problems back then were overcoming the personal fears of high-pressure air, getting dive shops to fill the tanks for non-certified persons and, of course, adapters.

The adapter problem continues to be bad, though there are movements to standardize at Crosman, Daystate and in the aftermarket. But the tanks themselves are more critical now than ever before. That’s because the guns of today need more air than they used to.

Size doesn’t matter
Here is the problem. The physical SIZE of the scuba tank means next to nothing. What MATTERS is how much air it holds. You say, “Of course!” But until you become a PCP user, you don’t really understand what that means.

The most common scuba tank
The standard scuba tank today is an aluminum 80 cubic-foot tank that’s pressurized to 3,000 pounds per square inch (psi). The physical tank measures just under 30 in. high by about 7 in. in diameter. It weighs just under 40 lbs. when filled (mine weighs 38.5). All these specifications will vary slightly from manufacturer to manufacturer.


The most commonly used scuba tank in the U.S. is the 80 cubic-foot aluminum tank.
And it will completely fill a PCP rifle that needs 3,000 psi one to three times, depending on the volume of the gun’s reservoir. AirForce rifles have a huge 490cc air tank get about two complete fills from such a tank. Remember, I’m now talking about complete fills to 3,000 psi.

After a full fill come partial fills
After that, the rest of the fills will end at less than 3,000 psi, because the scuba tank’s pressure has dropped. Taking an AirForce Condor as an example, each successive fill could look something like this:

2975 psi
2925 psi
2870 psi
2850 psi
2815 psi
2755 psi

And so on for about 15-18 fills. When the pressure in the scuba tank drops below 2200 psi, there isn’t enough air left to fill the AirForce tank high enough to get the gun on the power curve. That means you have to get the scuba tank refilled.

Actual results will vary
The actual number of gun fills you get varies, based on how low you allow the gun’s tank to decline before refilling and the size reservoir you’re filling. So the numbers I’ve just given are approximations. Don’t try to create mathematical formulae based on them–they’re just general observations.

Get a bigger tank
If you want more fills, the solution is to get a tank that holds more air. In the scuba tank world there are aluminum tanks rated to hold 100 cubic feet of air at 3300 psi and steel tanks rated for 120 cubic feet of air at 3500 psi. Obviously, these tanks will give you more complete fills of any PCP than the 80 cubic-foot aluminum tank. The 100 cubic-foot aluminum tank is larger than the 80 cubic-foot tank, but the 120 cubic-foot steel tank is about the same size as the 80 cubic-foot aluminum tank. The 3500 psi steel tank weighs about five pounds more than the 80 cubic-foot tank. Both of these larger tanks cost more than the 80 cubic-foot tank. You have to look for sales when buying tanks like this.

Smaller is more
Then there are the tanks made of carbon fiber. They’re actually aluminum bladders wrapped with carbon fiber fabric. They seem to be contradictions, because they’re smaller and lighter than 80 cubic-foot aluminum scuba tanks, yet they hold more air. My 88 cubic-foot tank is 24 in. by 7 in. and weighs about 20 pounds when filled to 4,500 psi. It will completely fill the AirForce reservoir perhaps 7 to 9 times and will get many more partial fills than an 80 cubic-foot scuba tank. It costs several times as much as an 80 cubic-foot tank. So, as with most things, you pay for performance.

Carbon fiber tanks are rated to hold breathing air, but for land operations. They are most often encountered in rescue service operation.

So far, all I’ve talked about are the largest portable air tanks. That makes what I’m about to say meaningful. If I were shooting a big bore rifle that gets two or three shots per fill and needs 3,000 psi to be completely filled, an 80 cubic-foot tank would be inadequate. The tank that most smallbore PCP owners use today could not supply the air needed to keep a big bore operating very long.

But if I had a Benjamin Discovery rifle that has a maximum fill of only 2000 psi, an 80 cubic-foot scuba tank would be great! I would get a great many full fills and lots more partials from that tank. That’s why I pushed hard for the 2000 psi fill level when we developed the Discovery. Besides being easier to fill with a hand pump, it extends the use of scuba tanks many times.

Okay, Abe, that’s the first part of the report. Next week I’ll cover smaller scuba/carbon fiber tanks, tank valves and buying used. What I need YOU to do is ask me questions now so I can work the answers into the next report. The same goes for all readers who have questions.

105 thoughts on “Buying a high-pressure air tank – Part 1”

  1. BB,

    A BB Pelletier pellet. Now that’s something. Tiny o-rings on each pellet for that perfect seal? Or are you going for the depleted uranium core? Don’t worry, no one ever likes my ideas either!

    Saw the mint container comment. Nice idea. I like some of the older tins, too, that had a small hole you aligned in the side to drop a pellet into your hand…

    You do get some fun jobs along the way, don’t you?


  2. B.B.,

    Where does a compressor (like the one you showed at the LASSO shoot and the one you purchased at Roanoke) fit in this mix? Is it so expensive to fill tanks at a scuba shop or fire station that a compressor is a cost effective purchase?

    Somewhat off topic: You’ve made a case for a chronograph to determine your pcp’s ideal string of shots and to determine max fill pressure. What features should you look for in a chronograph and do you have specific brands that you recommend?


  3. Kevin,

    That compressor costs about $3,200. Is that expensive? It is for me, so I don’t own one yet. But because I test a lot of big bores it is becoming more essential every day.

    As far as chronographs go, I used to be a snob and thought that if it wasn’t an Oehler 35P, it wasn’t worth much. But ever since I did an extensive test of the Chrony while making a video I learned different. Now I use a Chrony Alpha about 80 percent of the time.

    All chronoigraphs are accurate enough, so it makes no sense for me to rate one over another. I like the Oehler because as a gun writer, I can’t publish articles with anything else. They are not accepted by readers yet. But they all work fine.

    You know how it is. Everyone expects an explorer to wear a Rolex, even though a quartz Timex is more accurate.


  4. JoshO,

    The decision depends on a lot of things. How much do you shoot? You would need to shoot at least a thousand rounds a week to justify a compressor, and then it would not be cost-effective but only convenient.

    I shoot 25,000 to 50,000 shots per year, and many of them are from a PCP. Still, with all of that I have used scuba tanks, hand pumps and now a carbon fiber tank.

    Eric Henderson shoots as many PCP shots as I do, but they are all big bore. And he supports hunts and competitions with air. For him the compressor is essential.

    And the type of compressor you get matters, as well. A ruggedized military compressor like the one I got at Roanoke this year (but still have not put into service) costs about $1,800, but it will last longer than I do. A similar compressor has served AirForce Airguns, who test thousands of valves and guns each year, for the [past 10 years. It shows no sign of weakening. The FX compressor, however, which is an electrified hand pump, can be worn out in a few years by a single user. And it costs just as much.


  5. B.B.,
    Thanks for the info on tanks. The choices can be very confusing.
    I ended up getting a new scuba tank, a high pressure steel 100 cuft which is rated at 3442 psi. I checked prices on-line but my local dive shop had a supplier that was runing a sale and the tank and valve was only $175. Fills are $6. With the popularity of paintball these days, the shop I use understands the importance of getting a max fill, BUT ONLY IF I remind them. Most scuba folks aren’t real concerned about a max fill because they can run their tanks down to a couple hunderd pounds. For us, they are useless below a couple of thousand.
    If you get friendly with the folks at the dive shop, often they will put a few hundred extra pounds in the tank to “allow for pressure drop as the tank cools.” Many tanks have a “rated” pressure, and a maximum “overfill” pressure.

    I think my points are (for scuba tanks):
    1) meet the folks at your local dive shop. Even if they don’t understand airguns, they will be familiar with paintball.
    2) Ask them to check with their suppliers for special sales on high pressure tanks.
    3) Let them know that you want a nice maximum fill.

    B.B., I will be interested in the 4500 psi pony bottles. The paintball ones all have 850psi regs built in which I had to gut to get 4500 psi out of the valve.
    There must be a better way. Also, are paintball shops the only place to get a 4500 psi fill?


  6. Kevin,

    Yup, you got it… That’s why I say don’t go too far down the springer road… stop with a R-7 or the like at 600-700 fps.. then move into the PCP world.. So you won’t be taking a loss on reselling, and wasting time with high powered springers.. There is a FX Timberwolf .22 cal on the yellow for $500, I think it was. I sure like mine.

    It will be interesting to see what niche the new Disco takes.

    It is important to form a relationship with the owner or manager of the scuba shop where you buy and fill your tanks. If they think your just there for a $5 refill, then you could wait along time, and not get a “topped off fill”. The temp. that the tank is filled in matters. I started with two alum. 80cu ft. tanks $150 each. I spent time looking at the diving outfits, so they thought I would get into it in the future.. I did buy a cheap wetsuit for swimming.

    They do worry that you will buy the other parts so you can dive without being certified… so make them feel sure you won’t!!

    I ended up with 3 – alum 80cu. ft tanks, and 3- 100 cu. ft and one 120 cu. ft. They marked them with our name, and now I just drop off the empty ones and pick up the full ones on account. It takes 2 mins. on the way for supplies and the center fire/rim fire range.

    Again, if they know you, and trust you, then they can fill a 3,000 lb tank to 3,300.. You have to keep them out of the sun and heat, if they will do that for you.. I was told that they easily hold 3,500 and are tested to 4,000 plus, so the risk is low, if they stay out of the heat.

    Like I said before, and B.B. pointed out too, get a Discovery too. Or USFT, both like only 1,800 lbs. Or just a Disco, if that is possible.. We just proved that most of us can’t stop at one air gun.

    Then you can use up the low pressure, when you can’t fill the 3,000 lb guns anymore.

    One might see what kind of a deal the local scuba shop would give you on tanks and refills, before buying a pump.

    The other issue is clean, DRY air, that MUST go into the scuba tanks.. I’m not convinced that hand pumped air is as good. Even if the water trap catches most of it.. We just heard of water in the tanks of guns, being normal.. OUCH. I don’t like that idea.

    I should see if there is any water in my S410 that I bought new and has never been filled with anything but a scuba tank…

    Ashland Air Rifle Range

  7. B.B.
    Excellent report sir!! In the next report… May you talk about:
    1) The difference between a 60cf scuba tank that holds 3300psi vs. an 80cf scuba tank that holds 3000psi??? (you already explained that to me in a previous post, but for others entering the PCP world like me… LOL)…
    2) What is the difference between a Pony tank and a normal scuba tank… I mean, I see pony tanks smaller than normal scuba tanks, but much more expensive… Why??

    You know, yesterday I went to the Scuba Shop… and I witnessed a Hydro test… And I remember the blog in which you said that Hydro tests are performed underground, etc etc…. There, they make it inside a huge steel cylinder containing water… I saw the complete procedure and it was very interesting… Another thing, I would have never imagined that the letters and numbers stamped indicating the Hydro Test date, serial number, etc etc, was done by hammering down steel letters!! I thought that it was with a flametorch or something similar… Take care sir… And everyone else, Happy Holidays!!

  8. B.B.
    Excellent report sir!! In the next report… May you talk about:
    1) The difference between a 60cf scuba tank that holds 3300psi vs. an 80cf scuba tank that holds 3000psi??? (you already explained that to me in a previous post, but for others entering the PCP world like me… LOL)…
    2) What is the difference between a Pony tank and a normal scuba tank… I mean, I see pony tanks smaller than normal scuba tanks, but much more expensive… Why??

    You know, yesterday I went to the Scuba Shop… and I witnessed a Hydro test… And I remember the blog in which you said that Hydro tests are performed underground, etc etc…. There, they make it inside a huge steel cylinder containing water… I saw the complete procedure and it was very interesting… Another thing, I would have never imagined that the letters and numbers stamped indicating the Hydro Test date, serial number, etc etc, was done by hammering down steel letters!! I thought that it was with a flametorch or something similar… Take care sir… And everyone else, Happy Holidays!!

    P.S.: Wayne, I agree with you… Where I live (Puerto Rico) the humidity is extremely high… The first time I pumped the Talon SS tanks, I was amazed at how much water came out after bleeding the pump… Should bleeding be done slowly or can I just open it all the way fast??? Just curious…

  9. Jony,

    I added your items to the list.

    When you bleed, open the bleed valve fast! Some guns, and I include AirForce in this, will loose some of the fill if the bleed is too slow. Remember that the inlet valve is being held open by the air pressure in the fill line. Bleeding fast allows the inlet valve and return spring to build momentum to close the valve and prevent air loss.

    Also, the faster you bleed the more moisture is blown out of the line because of the violence of the air movement.


  10. B.B.,

    Is it common to use a two stage regulator to set fill pressure?

    The math isn’t that hard.


    where P is pressure, V is volume and Qty is a “quanity” of gas (forget units…). Idea is that you’re moving Qty from higher pressure to lower pressure.

    490cc = (2.54^3)/(12^3)= 4.6 cubic feet

    4.6*P_end = 80*(P_start – P_end)

    P_start = 3000

    4.6*P_end = 240,000 – 80*P_end

    84.6*P_end = 240,000

    P_end = 240,000/84.6 = 2836

    This ignores non- linearity of PV relationship and volume of filling hose. But it is a pretty good first approximation. Good within 5% I’d guess.


  11. B.B.,

    A one stage regulator is what I expected. Basically there isn’t any regulation, you’re just measuring fill pressure of rifle.

    A two stage regulator would measure pressure of tank and allow you to set a desired fill pressure. So if rifle had a valve lock at 2800 psi, you could set the secondary regulator to 2800 and start off with full power shots. You wouldn’t get many fills though at 2800 if the starting pressure was only 3000.


  12. Lloyd makes a good point about buying new by asking your local dive shop if any sales are going on. I bought a 80 cu.ft. steel tank off of Craig’s list for $40 and thought I was doing great. It was rated at 2300psi which is fine for my Disco. Unfortunately, it hadn’t been hydrostatically tested since 1978. These babies have to be tested every 5 years by law. With the test, the visual inspection and the repaired valve, I was at $135 total outlay. Another $15 probably would have gotten a brand new high pressure aluminum tank. On top of that, I still needed a yoke, pressure guage and high pressure hose and Foster fitting – another $150. Caveot Emptor. Wait, did someone say there’s a used FX on Yellow for $500?

  13. ajvenom,

    I’ve been thinking of something like that at the sight in range, especially with some of the higher power PCPs that get so few shots per fill..

    Ashland Air Rifle Range

  14. Herb,

    I believe the cascade systems dive shops use to fill their large storage tanks have regulators like you describe. But an airgunner can still use those below-maximum fills. They just get fewer shots in the power curve. So self-regulation remains the most practical way to go at the individual gun level.


  15. Sorry, should have just stated my concern more directly. If you have a Discovery, but get a tank rated to 3500 psi, then you could fill Discovery (1800 psi fill for no valve lock) to nearly twice its rated pressure (3500 vs 2000). Valve lock would be annoying but not dangerous. Overfilling could be dangerous.

    A two-stage regulator would be nice for Discovery in that you could set it for an 1800 psi fill and get many fills to exactly that pressure without the risk of over pressurizing the rifle.


  16. Kevin,

    A Chrony is essential even if you stay with Springer’s. You can make your own lighting with a simple swing arm attached to your workbench. This way you can diagnose if one is sick, know the effects of a tune, test pellets, etc.

    The only rifle I would say is also mandatory in addition to the R-7 that Wayne mentioned is a nice fixed barrel rifle with more power. However, half the fun is learning that on your own.
    (PCP’s are not supposed to be stored at full pressure, so they are not instantly ready like a Springer. )


    History channel had a great show on “Extreme Marksmen” try and DVR it if you can. The shots were ok, but the slow motion views were outstanding.

    Lost count of the actual number, But No 75. Gave your garage door a tune with JM products and wondered if he could supply a custom spring.

    Oh, I’mmm Backkkk


  17. Herb,
    You might want to recheck your formulae. The first one should be
    490cc = 490 * 1/((2.54^3)(12^3))= .017 cubic feet, not 4.6 cu feet.

    The problem with trying to do these conversions is that scuba tanks volumes are rated at standard temp and pressure (uncompressed), and the tanks on guns, and paintball tanks are rated at actual dry volume. That’s why a 3442 psi 100 (approx 756 cuin) looks about the same physical size as a 3000 psi 80 (approx677). Comparing apples and oranges.

  18. Herb,

    Actually if you wanted to regulate the Discovery, the output pressure would be set at about 1200 psi, or so. You set the reg to output the ideal pressure for the valve, not the max fill pressure.

    While that sounds like a great thing to do, the reg and the chamber after the reg that holds the air for the valve would be so large that it would remove a large volume from the reservoir. In the case of the Discovery, that would clip off a high number of shots.

    Your shot count might increase over a stock Disco, but not as much as you might hope. The shots would be more consistent, though.

    However, as I have said several times, the greater the pressure drop a reg has to handle, the shorter the reg’s life. Someone has mentioned that paintball regs last a long time, but I don’t know how they do it. Belleville washers are pretty much all the same.


  19. B.B.,

    It was A very good for Crosman to bundle the hand pump with the Discovery.

    My question to you is: Would it be at all Feasible for Crosman to bundle A carbon fiber tank with the new Discovery when it comes out?

    It seems to me, that if they could, it would take some of the angst away that some new shooters might have. There would be no worry about the right tank and the proper fittings among other concerns.

    I know that I would be near the front of the line if they did something like that.

    BobC NJ

  20. RE: conversion of 490cc to cubic feet


    You are absolutely correct. I botched the volume conversion. If you grind through rest of equations the numbers would be right. With volume of hose, you could use about 0.02 cubic feet and come pretty close to being right I’d think.

    I don’t understand your point about the scuba tanks vs tanks for guns. Trying to read between the lines, are scuba tanks are rated for how much air they will deliver assuming a cut off at something like 200 psi minimum pressure? (i.e. scuba tank is “empty” when pressure drops to something like an internal pressure of 200 psi or so?)


  21. BobC NJ,

    It would good for Crosman to “brand” their parts that work with Discovery on their website by quoting their part numbers of the components that are designed to work with the Discovery. Then you could be sure that you were ordering all needed parts.

    The thing that annoys me is to find out that after I get some basic new purchase that I have to invest additional funds just to get it to work. (Eg the infamous “batteries not included…”)

    The problem with putting too much in “package” is that the price point keeps climbing. It might be ok to bundle like the degassing tool, since it would add minimal cost to the package. However a carbon fiber tank is a significant expense.

    I do think that since the rifle is designed to be filled directly by the pump that the minimal parts should be the Crosman “package” for the first time PCP buyers. The whole point with the Discovery was to create a “total” package for a new group of PCP shooters.


  22. B.B.,
    The info you requested on the bottom of the candy tin.

    Clik Clak
    Areka-CD 158 78930 GUERVILLE
    TEL: +33 (1) 30 42 64 00
    FAX: +33 (1) 30 93 92 34

    After thinking about it. The design has one flaw. You’ll need a foam pad on the lid to avoid potential damage to pellets when pushing down on the lid to oopen it.

    Still though the tin is cool. It makes an audible click when you open and close it. And the locks very tight.

    New premium pellets… cool.


  23. Volvo,

    I agree, the silencer article is scary. I'd buy a rifle that had a factory installed "moderator" figuring that the feds would go after the manufacturer not me. But I wouldn't do any home modification, nor buy an aftermarket product. Just a nervous Nellie.

    Post 9/11 nobody in law enforcement wants to be identified as the person who let some terrorist loose. So if you get swept up in some snafu, then you're in jail until the whole issue gets sorted out.

    When I worked for IBM in the manufacturing environment, there were two questions that you should never ask. First "Is this safe?", and secondly "Is this legal?" Either question got you mired with gentlemen in endless discussions that had to be concluded before you could proceed.

    The "selective" enforcement of laws is shameful. Ignorance of the law is supposed to be no excuse, but all the laws that apply to me would fill a library. How the !@#$%^&* am I really supposed to know and understand all of that?


  24. Herb,
    Scuba tanks can be sucked down to zero. Many divers found that out the hard way. The 200 psi cut off is not a physical cut off but a strong request by the dive shop not to run their tanks completely out of air. Actually, most dive operators request a 500-700 psi reserve on exit. If you bleed a scuba tank completely dry you allow moisture to enter the tank and that is very bad for scuba tanks. It makes them corrode inside. Remember, the best dives are in salt water. Salt in a scuba tank is nasty, nasty. Also, Scuba shops do not want to waste time removing valves to dry out tanks before refilling.

  25. Herb,

    I follow a similar path, hence my recent FX Whisper. Factory “quiet” it was designed with the USA market in mind.

    I thought I had read some time ago that one of the UK imports that came with just a glued on moderator was $200 more then the STD model. Seems $$ solves most issues.

    I believe the latest factory creations are a little more high tech.


  26. Herb,
    Talk about ignorance of the law and “How am I supposed to know?”. My favorite book is “Hitchhiker’s Guide to the Galaxy”. You may have seen the movie. At the beginning of the story there is a discussion about how Earth shouldn’t go acting all surprised that a galactic bypass was being built right through the planet because the plans have been on display in Alpha Centauri for fifty years and if Earth can’t be bothered to take an interest in local affairs, well, that’s their problem. Whereupon Earth is demolished to make way.

  27. B.B.,

    RE: two stage regulator

    I was talking about a second stage between tank and rifle reservoir to fill the rifle to a certain pressure. Thus the first stage would measure pressure in tank itself. The second stage would be adjusted to whatever pressure to which you wanted to fill the rifle. This two stage regulator would not be subjected to the sudden pounding due to firing rifle. So I’d expect it to last a very long time.


  28. Volvo,

    Thanks for that link. I read that story yesterday. Reading between the lines, I think they were intentionally sneaking that silencer in for their buddy and got caught. I think the feds sent a message they hope will be heard far and wide.

    No British airgunner is unaware of the U.S. law concerning silencers — especially not those with airgunning friends over here.


  29. What is a LDC? Looks like a muzzlebreak.

    I guess people do use smaller remote regulated HPA tanks in their Co2 to HPA conversions.

    Darn Yellow Classifieds, all the awsome airguns I always wanted, but I’m to cheap to buy any of them.

  30. I am interested in buying the benjamin discovery and scoping it. Is the Gun/scope/pump combo a good deal? Is there a better scope combo with the benjamin you can get for around the same price?

  31. Anonymous:
    Yes you may… With P.A., I believe that you can substitute the scope that comes with any rifle with the one that you like… But you will have to pay the difference IF the scope costs higher… or less if it is cheaper….

    B.B. and Everyone else!!
    Well guys, tomorrow I will be leaving on vacations to Dubai until December 30th…… So I just want to wish you all Merry Christmas!! Enjoy the quality time with your family AND your rifle… Hope that every one of you receive what you wished for, either material (more rifles or accessories.. LOL…) or health which is most important.. It’s good that you are feeling better B.B…. Hey Wayne, too bad I won’t be here for when the pellets arrive!! LOL… but my brother is ready to receive them… So you can guess what will be the first thing I’ll do when I get home!!! LOL… easy answer…….
    Oh, one more thing… I went to the range today with my Gamo Whisper… and I recommend you all to ALWAYS wear glasses (I know most of you experts and wise airgunning men and women do), but I refer to does like moi who don’t… Today, while I was shooting, there was this guy shooting a Glock (don’t know if it is spelled right)… and one of his bullets fragmented when it hit the wall and one of those fragments ricocheted and hit me in the cheek… It left three scratches, one of them bled… it hurt at first, so imagine if it had hit me in the eye… No Dubai tomorrow!!! LOL…. So people please, I never imagined it could happen, but it does!!

  32. What about a XS Scuba X7-80 3442psi Tank. I got one of these: name brand, reasonable cost, and the local dive shop will fill to 3500 psi. Mine has a conversion valve so I can use either the clamp mount adapter or (as I prefer), a DIN adapter. Martin at AirHog has been very accomodating re making an Airforce DIN adapter and then fixing it when it later leaked. I think the fill to 3500 approach is good as it is commonly available (not so with 4500), and it gives you a number of fills at full rated pressure (3000).

    PS – don’t mess with SCUBA guys – these tanks are heavy and they regularly carry around two of these with all the rigging! My buddy gets mine filled for free as he is such a big customer of the shop (and I can count on him visiting there every week).


  33. Forgot to mention. BB says don’t bother trying to calculate….Here’s another reason he is right – it’s already done for you:



    PS for BB I was just thinking about the perfect pellet speed (as I have a lot of different ones and they all have their own positive characteristics). I arrived at around 900fps as 1) it can be done with a springer or a pcp, can be accomplished in relative silence, it hits hard, but not massively so (OK, super heavy pellets cause issues with that statement), and it has a relatively long point blank zero. Got any blogs out there on a topic like that?


  34. Herb,

    You don’t need a two stage regulator. You can use a single stage regulator that has a pressure gauge before the regulator (measures tank pressure) and one after the regulator (measures output pressure). I don’t know if anyone makes one for SCUBA tanks.

    JDS Air Man sells a 2000 PSI regulator, but it only shows the output pressure and won’t fit a SCUBA tank. It is made for paintball tanks.

    You don’t really need to know the tank’s pressure except when filling it. The output pressure should stay fairly steady until the tank pressure drops low enough that it needs filling.

    .22 multi-shot

  35. Herb,

    The bottom line is…If your gun doesn’t have a gauge. The yoke that goes on the scuba tank has a gauge.

    When you hook up the gun to the tank, and gentle open the scuba tank valve, the gauge on the yoke instantly tells you the pressure in the tank on your gun…. slowly open and fill your gun slowly… if you just crack it open, it takes 5 mins to fill the gun… crack it a little more and your in control for a perfectly slow fill… don’t worry…

    Ashland Air Rifle range

  36. Jony,
    You envey us for living in the mainland where we have lots of open spaces. That is understandable.

    I envy you the nice weather, wonderful beaches, and low taxes. It is snowing outside right now… and tax season is just about to start. So maybe it is a wash.

    BobC NJ,
    You can buy a Benjamin 72ci HPA tank. It includes a 2000psi regulator, a gauge, and says Benjamin on the side. It does not come with the hose though… have to buy the Dual Fuel Adapter to make it work.

    Disco degassing tool can be derived by buying a 3″ 10-32 screw at the hardware store. Cost is about 35 cents. The Dico tool is much more robust and easier to use but the effect is the same.


  37. Guys,

    RE: Two stage regulator

    Understand that a two-stage regulator isn’t required. Just seems that it would be a nice to have.

    But I do worry that a Discovery filled to 3500 psi from a scuba tank would have a nasty failure. (Is there something that I missed that would prevent this?)But even a two stage regulator isn’t idiot proof. Idiots are extremely ingenious!

    The pump that Crosman packages with the Discovery wouldn’t go that high of course.

    I’m also concerned about the valve stem on the scuba tank as I indicated before. I handled gas cylinders for a long time in a chemistry lab. You never moved or transported them without a valve cover over the valve stem. It is just a safety issue that I would want. I’m sure that some diver somewhere has broken off a valve stem with catastrophic results. I just can’t imagine having the cylinders rolling around in the bed of a pickup.


  38. Good evening all: Jony enjoy Dubai. Maybe Wayne would consult with you for the First Foreign Wacky World franchise.:) All the guns you want to play with for the business. (B.B. picture a Persian percusson gun and transfer the enlays from it’s stock to a custom FX stock, what a funny mental picture.) Jony have a safe flight coming and going!

    Volvo, it’s nice to read your voice again. Welcome back.

    Now my question please. A day of woods walking and plinking with the Talon SS requires more than a single fill of air. How and why do you carry your air supply? Pump, tank, what size, steel aluminum, carbon fiber, or another tank from AirForce? Thanks guys.

  39. B.B.,

    You sure filled a void with this blog. Over 60 comments so far.


    Thanks for the info on dive shops and your experience in filling all your tanks. We have a dive shop 5 minutes from our home in the city. I’ve been a certified diver for almost 15 years and my wife has been certified for almost 35 years. We’ve never owned a scuba tank. Common reason. No desire to dive in our fresh, cold water reservoirs and traveling with tanks is not economical. Every dive boat includes tanks in their fees. We know the dive shop owners since we purchase goods frequently and must have our regulators serviced annually in order to stay under warranty. Thanks again for your insight since this is a new dimension. Appreciate your heads up on the fx timberwolf. Thanks.


    Thanks for the additional justification for a chrony. I’m starting to gasp for air at the entryway of pcp land. Are there any other surprises lurking around corners that will cost me?


  40. Mr. B.

    Thanks for the welcome. Turned out I was sidelined by a bad power supply.

    I think everyone is done with these, but number 85. You remove the screen from the center Great Room window and tell the wife it is for an unobstructed view of yard.
    You forget to mention the shooting opportunities it provides.


  41. BB,
    Today’s blog just about cured me of my desire for a PCP:). The options seem to be: 1) pump every 20 shots or so; 2) buy a $2K electric or gas-powered pump; 3) learn a lot of esoteric stuff about SCUBA tanks and find a SCUBA place — can’t tell you how many dive centers are located within a mile of me:). Springers seem more like my speed.

    Just don’t clean the window too well. Read about more than one shooter who shot through a crystal clear window or glass door. Glad you’re back; power supply problems are hard to debug.

  42. Kevin,

    A nice new or used rife, a hand pump, and the proper fitting is truly all you need to start. I believe I stuck a cautious toe in the water for about $675 total.

    Yes, my kit arrived in a Mon- Fri span, but that was not so bad. At least I was well acquainted with the components before using them.

    The pump with the disco was bigger boned, but the extra stage on the FX and the double moisture filter is very nice.

    I may someday get a tank, as about three fills an evening is all I want to bother with. I’m really hoping the compressors will become more affordable.


  43. Guys,

    Redoing the calculations,

    Convert 490 cc into cubic inches = 490/2.54^3 = 29.9 cubic inches

    Use Llyod’s infomation that finally cleared this up for me…

    100 cubic feet is compressed into a tank with an internal volume of 756 cubic inches at 3442 psi

    80 cubic feet is compressed into a tank of internal volume of 677 cubic inches at 3000 psi


    29.9*P_end = 677(P_start-P_end)

    707 *P_end = 677*3000 = 2,031,000

    P_end = 2,031,000/707 = 2872

    So drop of 118 lbs should be good to about 5%.

    For the second fill you’d have to take into account pressure left in 490cc tank since you’re not starting from empty. Not sure what pressure you’d stop at.


  44. Bg-Farmer,

    I have my own Quigley set-up. Take a small empty tomato paste can from after the wife makes the Sunday gravy.

    Put it at about 45 yards, then I use my kids Daisy 499. Great way to win a bet, since the 499 is meant to shoot at 5 meters.

    Don’t forget test it first, and then mark an aim point on the fence it is up against. : )


  45. B>B., Herb & D.B.,

    Thanks guys for your input.

    I've decided to get the Disco, and am willing to wait for for the new version. B.B., Any news on that front?

    D.B.- Ive been using Tic Tac boxes for about 4-5 years now. They are perfect pellet holders and have never had A jam LOL.

    BobC NJ

  46. RE: clean, DRY air & moisture filter

    I've even gotten fickle about putting air in my car tires. All the pumps at gas stations now that run off of quarters seem to have water in the lines. Can't be good to blow water into tires. Wonder if that is why the "nitrogen" craze started?

    I know of one gas station that has the old fashion air hose that I use once in a while to fill my tires. Buy a tank of gas from them at a somewhat inflated price, but I more than break even overall.

    I do think an honest to goodness moisture filter would be a good idea on a hand pump. I assume that you can regenerate them in an oven?


  47. Bg-Farmer,

    Never say never.

    If you try a PCP by 2016, you will still have beaten me in taking the plunge.

    As far as the number of shots, a nice 12ft lb rig will provide a bunch. Even my ancient technology Raider states it will give 70-80 in .22 cal if non-fac. For some reason, .177 (60 shots) is always less than .22 ? My fac version gets 30 shots at 22-24 ft lbs.

    The .177 Whisper gets about 48 shots before needing topped off. I think the shots don’t fall off to just 20 until you get to the small capacity tubes, or real high power rifles that only provide 10shots.

    Diminishing returns apply.


  48. Kevin, I’d include the option of running the gun on CO2, if that is an offered one. Great for targets and pests at 20 yard or so. A whole bunch of shots with no POI changes. They are alot quieter than PCP and no cardiovascular exercise involved.

  49. Here’s my guess:

    The new Disco will be:

    8 multi shot, with shroud.
    Larger air tank, 40 good shots.
    Stronger, free floated barrel.
    Power adjuster.

    $349 retail without pump

    Add a yoke and tank $225…Total $574.
    $5.00 per fill of air = 3,000 shots…

    How close am I?

    Just in percentage.. not on the each item..

    Ashland Air Rifle Range

  50. Volvo,

    I also want to try the Quigley challenge as I see it based on BB’s feedback: small tomato paste can at 100 or 110 yards. I think the can (6 oz.) is a little too tall in relation to its diameter, but its close to the right size. Your version sounds good, too — I bet the elevation adjustment is substantial. Did you hit on the first try:)? We need some better weather for this kind of thing here.

    You’re right: I’ve got a burr in my shorts about PCP’s right now, just because they’re different:). I’m also having trouble justifying any of them except a 10M model (where an SSP like the FWB 603 would work even better for me), just because when I need power and range, I’m reaching for a firearm.

  51. BB,

    This Abe reporting sir. Thank you so much for this post. I am expecting my first pcp in April 2009 and this blog will certainly help me towards my scuba tank. I am inclined to choose the used scuba tank at this point in time.

    My initial intel among the local dive shops here indicate that it is both safer and practical to buy from a particular dive shop and get refills from the same shop. Otherwise, they “implied” they will hesitate to refill on tanks they have no idea where I got from. They sell only used tanks they have certified as hydro tested.

    Now, I would like to know the process of charging from a scuba tank. What is the sequence of steps? By the way, I have also ordered a scuba tank adaptor with gauge on it. And my pcp will also have a gauge. Which one should I watch during charging?

    Will save this blog for reference. Thanks for the special mention. Happy Holidays and season’s greetings to all.


  52. Herb,

    Just to keep the record straight, the hand pump Crosman sells for the Discovery is rated to 3,600 psi. It is the same pump AirForce sells, though the fittings on the base are different.

    The dial on the gauge is made for the Discovery, but that pump is the highest-rated pump on the market. And with a Discovery, it should last for a long, long time.


  53. Wayne,

    Your guess is very close to the PCP rifle I thought Crosman should built next. I’m pretty sure it is a repeater and that it has a shroud, but beyond that I know nothing.

    I will be getting one to test soon but I’m sworn to secrecy until the SHOT Show (Jan 15-18).


  54. Wayne,

    Your guess parallels mine, even the pricing is where I thought it would be.

    B.B., Are you sworn to secrecy about the whole new Disco, or will you be able to drop us A little snippet about it from time to time?

    I am getting real antsy with anticipation waiting for more info on this new rifle, I can see myself opening the package and heading right to the big local sporting goods store and geting the tank filled for the first time.

    BobC NJ

  55. RE: BB & new discovery


    Yep he's sworn to secrecy. We'll no doubt get the information as soon as he can release it. IF BB tells us early he won't get another sample early. It's like that old ketchup commercial "anticipation…" So we'll just have to wait.


  56. Discovery,

    You need a fill clamp that connects your scuba tank to the Discovery. I assume the scuba tank has a K-valve and I know the Discovery has a male Foster quick-disconnect. So your fill clamp needs a hose with a female quick-disconnect on the end.

    This clamp


    and this fitting:


    Should work. If you buy from Pyramyd, have them guarantee the threads will interchange.


  57. Hope you will address the different fittings used for connection to fill line. I have a Sam Yang 909 and would really like to change fitting on gun to a quick disconnect. Other thing that would be interesting would be discussion of why scuba tanks require hydrotesting and recertification but our pressure vessels on guns do not. Proper way for us to inspect our pressure vessels after a few years would be interesting. Might want to also discuss difference between inspection process and tests for steel vs aluminum tanks and the different costs associated. Your article was very interesting to me. Wish I had read it when I first became interested in large bore airguns. Probable would have saved me quite a bit. Might also want to discuss shorter life of carbon tanks and the implications on relative cost.

  58. Hey, guys been awhile but wanted to say a couple of things since you are now in my area of expertise. I am a PADI Master Scuba Diver Trainer Instructor and Dive Shop Manager–mucky muck titles aside a few recommendations when buying tanks.

    There are low pressure tanks 2200/2250CF psi steel tanks(as someone unfortunately posted)3000psi aluminum tanks and 3300 psi aluminum tanks(only available as 100 CF) 3442/3500 psi steel tanks.

    You want the highest volume tank in the highest psi you can afford. The bigger the tank and higher the psi the more fills you'll get.
    I recommend a 3442 psi steel 130(commonly filled to 3700–but legally are only supposed to be filled to 'service pressure' on the tank)I do not recommend any 3000 psi tank unless you have a low psi rifle–and use that calculator on airhog and figure out your fills before you buy!

    The lucky guy that bought that steel tank for $175 got it BELOW cost.
    IF you are going with the 4500 psi carbon fiber call and make sure you can get it filled locally. Most scuba shops will not fill to 4500(too much wear and tear on compressor or they don't have one that can output that high).
    If you buy used make sure it is in current 'hydro' You can go here and it shows you how to id the hydrostatic date http://www.geocities.com/Baja/Canyon/9588/scuba_page/tank_markings.html
    If you see 12A08 or 12-08 that means it exipired on 31 November and cannot be filled until it is re-hydroed ($20-40)on top of that you have to have it 'visually inspected' (VIP)$15-$20 (should include free airfill). Anything older than 1993 (aluminum only)will not be be filled by a scuba shop(even if the hydro is current).
    So don't get ripped off that way. I don't recommend buying used off of ebay because you can't see the condition of the inside of the tank and most scuba shops will want to VIP an empty tank.

    Just so you know Dive shops can only fill scuba tank to certified scuba divers–but don't dispair just explain that it is for air gun use only(show them your air rifle if you have to). They can have you sign a Risk of liability and release form(some shops are afraid of fines/lawsuits and are hyper-vigilant). I recommend you get some of these stickers
    or use a FAT Magic Marker and write that on your tank in big bold 6" letters (NOT FOR SCUBA).

  59. 909 owner,

    I already covered hydrostatic testing here:


    and here:


    I addressed the types of scuba tank connectors here:


    AI think I have written about the different connectors as well, but I can’t find the report.


  60. Also forgot to mention that a viable option is renting a large cylinder from your local compressed air store Praxis or Airgas(welding supplies)large green (51 inches high)aviator grade air cylinders. These tanks hold 220 cubic feet at 6000 psi!!!
    They will deliver for you and bring you refills.
    You’d need a fill adapter–Van at Airhog can supply them.

    All you do is open an account and than you rent the tank for $8.10 a month(our local praxair price)and refills are $30.
    So 220 cubic feet filled at 6000 psi filling my Sumatra 2500 to 3000 psi in the 380cc reservoir and refilling at 2000 psi gives me a 120 refills!!! At a cost of 32 cents a fill! Now if you have a 80 cf 3442psi steel tank filling your rifle to 3000 psi in it’s 380cc reservoir and refilling at 2000 psi you’d get 11 refills which works out to 55 cents a fill ($6 fill cost). 100cf tank would be 14 fills at 43 cents 33 cents if you have a 130 CF steel tank. Now I haven’t added the initial cost of purchasing the scuba tanks orthe cost of an adaptor (I’m not that smart.
    Just something to think about.

  61. Jay Hodge,

    Great info! I started out at the gas/air supplier for our welding supplies. But they had no idea how to adapt it, or regulate it, for my air gun…

    So, Van at Air Hog is the guy… I’ll check that out again.. thanks.


    Ashland Air Rifle Range

  62. Hi BB, I just got a Daisy Powerline 953 with a leapers Bugbuster and leapers 2 piece high mounts. Windage is to the right 6″ at 10 meters. If I adjust windage all the way I am still to the right at 10 meters. What should I try?

  63. BB, I feel kind of foolish now. I swapped the back ring, Then the front ring and my point of impact moved over 1″ at 10 meters. I was happy and went shopping with my wife. Back home again I was planning to fine tune. I went all the way on the windage adjustment and it bought me over to within 1/4″ of where dead center needed to be. So I continued swapping. Front to back and then again a 180 on each. The best I could do at center was 1.25″ off. So, then I changed scopes, same 1.25″ off. Then I mounted the bugbuster with 1 mount and same thing. Swapped again and then used other ring and swapped. Finally I turned the parellex to the lowest setting and looked at the wall 5′ away under the mount. Lined up on the front sight and then raised my head to look through the scope. It shows the cross an inch to the left. Did the double swap on the rings and then with the other scope always the same.

    My conclusion is the dove tails are pointing off or the barrel is bent. The dove tail is my guess because the barrel is embedded in the stock and looks very rigid.

    Anyone else have this problem?

  64. Baja,

    Yours is a very common problem. I can’t get people to believe it, but it seems to happen a lot.

    I guess people believe that if they are mounting the barrel and cutting the grooves, they will go to extra effort to align them. My experience shows it to be pure luck when they line up.


  65. So, for adjustable scope mounts what do you think about the BSA adjustable? Item#:BSA-DBC120

    Or is your preference the BSquare adjustable mount? I have the BSquare adjustable on my Mod48 and it works well but was painfully slow to get setup right.


  66. Thanks BB, I will go with the B-Square 10037 1″ Interlock Adjustable Rings; By the way do you know how much windage adjustment they give? I looked on the website and the http://www.b-square.com/ site without luck, just wanted to make sure I had enough windage. Got looking at the mounts and figured the BSA mount or one piece B-Square would not work because loading would be too difficult.

    Thanks again for your expert advice! Baja,

  67. Baja,

    I don’t know how many minutes of angle the B-Square adjustable mounts have, but it is certainly several tens of minutes in both directions. It’s more than enough to correct your problem.

    You have discovered one of the many reasons why 2-piece mounts are preferred over 1-piece mounts.


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