This report covers:
- Depends on what?
- How long can CO2 be stored?
- Crosman 111
- Bulk-fill
- CO2 Powerlets
- Times and designs change
- SAFETY
- Summary
Today’s report is an answer to a question asked recently about how long CO2 can remain in an airgun. The answer isn’t straightforward. The correct answer is, “It depends…”.
Depends on what?
Before we go there, how long can you store gasoline (petrol for the UK, benzene for Russia etc.)?
Store it? In what? And that is the answer. How you “store” gasoline determines, to a great extent, the length of time it can be stored. Store it in a styrofoam cup and it will last only a matter of minutes because styrofoam breaks down in the presence of gasoline. The gasoline will soon leak out of the cup and either run away or evaporate.
Store gasoline in a sealed container like a gas tank and it can be stored for 2 to 3 months. If there is no ethanol in it (rare these days) it can last up to 6 months. It will eventually break down and the rate depends on several things with oxygen being the number one problem. Now let’s switch to CO2.
How long can CO2 be stored?
CO2 can be stored for decades, depending on the container. For example, consider fire extinguishers that hold CO2. They can be stored for decades with just inspections to ensure they remain sealed. But what’s that got to do with airguns? A lot, as it turns out. You see, some CO2 guns store the gas just like fire extinguishers.
Crosman 111
It was sometime in the middle 1990s when I bought a Crosman 111 CO2 pistol at a flea market. The lady I bought it from didn’t know how long it had been in the family. She said she found it in a drawer and I think she said it belonged to her late father. As far as she knew it hadn’t been touched in at least 20 years. It was in the original box and came with the manual and the model 197 ten-ounce gas tank.
A boxed Crosman model 111 gas pistol with the refill tank. This gem was found at a local flea market for $30!
I took it home and went to my basement range where I immediately dry-fired it to see if there was any gas left. There was so I loaded .177-caliber pellets and shot about 30 shots. Then I refilled the gun from the tank that came with it. In all I fired several thousand shots before needing to get the 10-ounce tank refilled. The pistol got about 70 shots per fill, so it was about half-filled when I got it — after at least 20 years.
Bulk-fill
The Crosman 111 is an example of a bulk-fill CO2 gun. Bulk-fill guns are like fire extinguishers; fill them and then let them sit for as long as necessary. Unless they develop leaks they will hold the gas forever.
CO2 Powerlets
First off, I call these 12-gram CO2 cartridges “powerlets” because Crosman called them that when they first started making airguns that used them, back in the early 1950s. Benjamin, which was a separate company back then, used 8.5-grain Sparklets, which is what the seltzer bottle companies called their cartridges. Benjamin made no attempt to brand those cartridges as their own. They just used them. Crosman, on the other hand, took an off-the-shelf 12-gram cartridge and made it their own. They made powerlets and sold them under that name and they are still called that today.
Crosman powerlets have carried that name ever since they were created in the 1950s.
So, why do companies warn us to not store our gas guns with CO2 powerlets? Let’s fast-forward to the 1960s. Crosman was making lookalike gas guns like the 38 C and T and the Marks I and II. The way they were made often required a short pipe to conduct the gas from the piercing screw to the firing valve. This pipe had two ends that were prone to leak.
This Crosman schematic of a 38C/T valve shows the pipe mentioned above. It’s part 38-065.
Gas guns of this era had pipes like you see in the image above. Those pipes could leak if left pressurized for long periods. At least that’s what Rick Willnecker of Precision Pellet told me. So those guns should be stored without a cartridge in them — except for one reason. Many of them use the cartridge to hold one of their grip scales. The 38T is an example of that. What I do on the 38 T is exhaust all the gas and turn the piercing screw out so the tip of the powerlet just touches the face seal inside the grip frame. There is no pressure on the face seaL and the grip panels are still held in place.
By leaving the empty CO2 cartridge in the grip, the left grip panel has something to grab. But the piercing screw is backed out to provide just enough tension to hold the cartridge in place.
Times and designs change
Today most CO2 valves incorporate the piercing pin within their body. Pipes aren’t as necessary as they once were. Leaving the cartridge installed isn’t the problem for such guns. However, leaving a cartridge installed with pressure against the face seal will flatten that seal over time and eventually make it leak. That’s a good reason to not leave a CO2 cartridge installed in the gun. But it’s not the biggest one.
SAFETY
Safety is the number one reason to not leave a CO2 gun charged when it isn’t in use. You see, if a gas gun is charged it will shoot anything that’s put down the barrel. You don’t have to load it; just drop something down the barrel. That’s an extremely unsafe way to store an airgun.
Folks who don’t know about gun safety may think the gun is unloaded and pull the trigger to see. If there is something down the barrel, it becomes a missile.
Kids may horse around and pull the trigger, thinking they are being funny. If there is something inside the barrel, it comes out with force and the “joke” is over. There are no second chances.
Anyone who is familiar with gun safety and practices it all the time won’t have a problem with a gas gun that’s charged. But there are more people who don’t know better than there are those who do.
Summary
So, what’s the answer? Can you leave a CO2 gun charged all the time? The answers are, “it depends” and “sometimes.”
“What I do on the 38 T is exhaust all the gas and turn the piercing screw out so the tip of the powerlet just touches the face seal inside the grip frame. There is no pressure on the face seaL and the grip panels are still held in place.
B.B.,
That’s the exact same thing I do with my old Crosman 357, and it works great. And, as you taught me, I never ever install a CO2 powerlet without first putting a drop of Pellgun oil on it! 😉
Blessings to you,
dave
B. B.
I wonder if some, little, pressure is harmful to valves. Excuse my ignorance but what I have in mind is the need of multi pumps and PCPs for some pressure to keep them healthy.
Bill,
Believe it or not, I’m new to this idea. You may be right, but I just don’t know what to say.
BB
Bill,
They are totally different critters. The air pressure helps to keep the insides clean, free of dust, etcetera.
I like to inject a little silicon chamber oil every few fills of my PCPs. If a seal is leaking, the oil will migrate to the leak and help seal it. It is also good for the seals. I can imagine it works well in multi-pumps also.
Any excess will be “blown” out and that will help protect the bore.
Just my thoughts.
R.R.
I take exactly the same steps with my PCPs, along with some left pressure. Do you think that some CO2 left, along with the pellgun oil would hurt in this type of guns?
Bill,
As far as CO2 airguns are concerned, I would recommend you follow BB’s recommendations above. I do not have much experience with CO2 and could not possibly recommend what to do.
R. R.
Unfortunately, believe it or not, it’s a new idea even to him. I’m afraid that I will have to test it first. I think it’s time to bring my 2240 out for heavy duty.
Been following that advice with the Maximi – the .177 has a slow leak, about 250 lbs/day, but the silicone treatment possibly might have kept things from getting worse. Something tells me the leak may be the air pressure gauge o-ring but FM may be wrong, as he is about a lotta things. Leaving things alone for now since the rifle shoots well and believe if something ain’t too broke, don’t try too much to fix it.
FawltyManual,
Don’t have a Maximi (Maximus either) but if you suspect a spot like the gauge O-Ring a few drops of water mixed with a drop or two of dishwashing detergent (pure Glycerin is what i use because i’m anal about CORROSION) in an eyedropper or needle applicator applied to the receiver/air tube to gauge stem point may give you some slow small bubbles for evidence of a small rate leak.
On Foster fill fittings i slip a latex balloon over the the tube end and wait for it to inflate. For large areas that the balloons are to small and not Stretchy enough to enclose the area of interest an unlubricated profilactic will cover and seal for a similar inflation test.
shootski
LOL! Sometimes I too should leave well enough alone.
Bill,
this is what I’ve been doing with my C02 guns for years. I let out most of the pressure, but I do leave just a little. Right or wrong I don’t know, but I haven’t had any problems.
Doc
Doc
Thanks a lot for saving me from testing. Anyway tomorrow is trigger time for that vintage/classic 2240. It’s going to be 18 degrees Celsius here…
Powerlets sometimes do not last a day 🙂 because of the leakage. I think simple as this: when you will use it put the powerlet in and shoot until it is empty.
I am fortunate that I have but one CO2 gun to deal with, a 2240. It is easy to exhaust a cartridge during a shooting session. I like to remove it all the way.
I am attempting to rebuild a Crosman 150 for my grandson’s friend. It belonged to his grandfather. I do not yet know what the seals are like. I need to get a piercing cap for the cartridge chamber, then hopefully a little Pelgunoil or transmission sealer will fix it. If not, I will have to get a rebuild kit.
Tom Gaylord (B.B. Pelletier), sounds to me like you got diddled on that Crosman 111, ie isn’t $30 a bit too cheap? 🙂
I love this profound statement: “Unless they develop leaks they will hold the gas forever.” 🙂
Because of what they look like, I call those gas thingies ‘little CO₂ bottles’, and pictured below “Crosman Powerlet ® CO₂” is also the word “Bouteilles”, which is French for bottles. 🙂
I do not think, a gun charged with CO₂ to be safe. To store, for example a gun with a partially used 88 gram CO₂ bottle in it, would need some serious extra something, to prevent it being accidentally shot. 🙂
hihihi,
Fortunately, Umarex now sells the CO2 Gas Saver Adapter for use with the 88 g / 90 g CO2 cylinders. The check valve in the adapter valve stem allows the CO2 cylinder with the adapter to be removed from the gun without losing the remaining CO2, thus rendering the unloaded gun “safer”.
Unfortunately, the CO2 Gas Saver Adapter works best only with the Hammerli / Umarex 850 air rifles.
With older Umarex air rifles, like the Beretta CX4 and Walther Lever Action, the adapter can be used on the CO2 cylinder, but the stock end caps can’t be reinstalled while the rifles are in use. For these two rifles I use the Umarex 2 x 12 g adapter most of the time.
With respect to the Sig Sauer MCX / MPX CO2 rifles, your comment about safety with a loaded partially used CO2 is valid. Unfortunately, the MCX / MPX rifle frame will not permit the Umarex Gas Saver Adapter to be screwed in far enough to work with these rifles.
cstoehr,
Perhaps one of these: https://nmproducts.ltd.uk/webley-88g-co2-air-saver-adaptor-for-airguns-airsoft-paintball-one-way-valve-system
That check valve would allow refills from a bulk tank of CO2
shootski
shootski,
Thanks for the link. Unfortunately, NM Products says on their Delivery Information page, “We deliver to England, Scotland, Wales only.”
I’ll have to do some searching for a U.S. distributor, possibly Amazon or one of the other U.S. airsoft equipment suppliers.
cstoehr,
I saw that too!
Just knowing that it does exist makes finding one you can access gets easier.
If it coms down to it a blog reader in the right place may volunteer to ship one from their homeland. I have done it any number of times as long as it is legal at both ends.
I think you will find it!
shootski
shootski,
I’ve already found some possibilities at Amazon.com. Check out these links for adapters to use 12 g CO2 with MCX / MPX.
https://www.amazon.com/None-branded-Cartridge-Adapter-Instead/dp/B08F3GRSJ4/ref=sr_1_10?keywords=88+gram+co2+adapter&qid=1679538561&sr=8-10
https://www.amazon.com/Change-Cartridge-Adapter-Capsule-Threads/dp/B08LDG1H7S/ref=sr_1_6?keywords=88+gram+co2+adapter&qid=1679538561&sr=8-6
https://www.amazon.com/Change-Cartridge-Adapter-Capsule-Threads/dp/B08CZC6F98/ref=sr_1_4?keywords=88+gram+co2+adapter&qid=1679538561&sr=8-4
I just now found a link for another 88 g / 90 g gas saver adapter that says it will work with the Sig MCX / MPX.
https://www.amazon.com/Heyxire-Adapter-Cartridge-Different-Suitable/dp/B0BJP3H5RB/ref=sr_1_24?keywords=88+gram+co2+adapter&qid=1679538561&sr=8-24
cstoehr,
Glad you found you have choices!
I have big 7 1/2oz and 20oz bottles for one of my old Tri fuel .25 and 9mm rifles. I usually use it with regulated 3,000psi hpa or Nitrogen but occasionally i use the CO2 bottles. I put the empty bottles in the freezer and chill them down before i use the big 20Lb Tank to fill them. When the cylinders are pre-chilled you can usually get a full (by weight) fill on the first try since the CO2 all stays liquid. If I get an overweigh fill I just bleed of the excess or start shooting immediately ;^)
shootski
Thanks cstoehr for your comment. Didn’t know about the Umarex CO₂ Saver Adapter. I hope the people behind the 88g bottles are suitably embarrassed. 🙂
Anyway, I’m also quite happy shooting my Umarex Walther LeverAction with a Walther CO₂ Adapter for 2x12g. I like that it allows me to load just one full little CO₂ bottle (leaving the second little bottle empty). 🙂
hihihi,
I like the Umarex 2 x 12 g CO2 adapters as well. I just wish they had valve stems long enough to work in the MCX.
cstoehr,
Both of those Umarex adapters work with the AirSaber as well.
BTW, NEVER screw a bottle onto an AirSaber when it is loaded with an arrow. I put a hole in a large screen Smart TV the one time that I made that mistake and was glad that that was all that happened. A little imagination will show you how bad it could have been.
Half
halfstep,
Don’t make the mistake I made the first time I tried to use the Umarex gas saver adapter. Because the adapter was delivered without instructions, I foolishly thought that screwing the adapter on “hand-tight” would be good enough. After a long career in analytical laboratory science working with high pressure gas cylinders, I should have known better.
Naturally when I tried to remove the cylinder / adapter combo from my 850 Air Magnum, the cylinder came out alone, leaving the adapter in the rifle and exhausting the rest of the CO2.
I needed Umarex Tech Support to remind me to attach the gas saver adapter “wrench-tight” with a crescent wrench.
Interesting thought on the safety aspect. I suppose the same could be said of any PCP though . . .
Here is a twist on that – the only CO2 gun I have and use now is a Sig P365 BB pistol. That type of CO2 gun has the cartridge in the mag, and the mag can be removed from the gun with the CO2 cartridge still full (as it must be to reload it). What do you think about storing the mag separate from the gun with no ammo in it but with the cartridge still containing liquid CO2? I know it is probably not good for the seals, but any issues other than that? The only other one that comes to mind is that if the liquid vents at any point it will make whatever it comes in contact with extremely cold, including possible frostbite to skin.
Alan McD
Alan,
The face seal that seals the powerlet will compress that way but besides that I can’t see a problem.
BB
Have not had any trouble with leaks in the Umarex BB MP40; was leaving the two cartridges in the magazine but last time they emptied decided to leave them out to ensure the seal does not take a set or warps. Also, always dab each cylinder with pellgun oil before installing. Related to FM’s anal-retentive tendencies, also wrap some Teflon tape around the threads of the magazine nut or screw then tighten it snugly. It probably does not help but figure it can’t hurt either.
BB
Safety training comes first! No matter whether firearms, airguns, darts, catapults or slingshots.
With the above understood and as much a habit as breathing I admit to leaving CO2 powerlets in guns that contain two CO2 powerlets but try not to in single powerlet guns. I have read in this blog (if not you then from readers) that the seals don’t crimp in guns that use two powerlets. I’ve been doing this only 3 to 4 years with no problems so may be too early to be conclusive. My Beeman AR2078A happens to get 100 good shots at 25 yards from two powerlets and it came tuned that way from the factory. The manual claims less than half that number. (Conversely my Crosman 160 which has similar internals only gets 25 good shots.) I say this because I rotate all my goodies and shoot several guns at a sitting. No way I’m going to shoot 100 pellets from one gun on the same day.
Very informative report today and I await either conformation or rebuttal.
Deck
Deck,
You know, you just brought up a class of CO2 guns that I didn’t address. It’s not just the ones that take two cartridges, because the Crosman 180 and the 1077 also seal differently.
Oh, my! I may have to write a Part 2.
BB
B.B.
Referring to my reply to hihihi above, do you know or can you find out if Sig Sauer came out with their own version of a CO2 Gas Saver Adapter for the CO2 versions of the MCX and MPX?
I know I could convert my MCX to use high pressure air, but I just don’t want to do that.
Charles,
Sig did not have a gas saver. But you could make one instead of using high pressure air.
BB
B.B.
I could make one? While I’m reasonably handy with common household tools like screwdrivers, saws, wrenches, etc., I can’t imagine how I could make an adapter. Do you have suggestions on how I might proceed?
The Umarex adapter fails because the valve stem is not long enough. Is there a way to use the high pressure air adapter with the CO2 gas saver adapter or with the CO2 cylinder directly?
B.B.
shootski got me started on an internet search for adapters by other manufacturers. Check out this link at Amazon.com.
https://www.amazon.com/Heyxire-Adapter-Cartridge-Different-Suitable/dp/B0BJP3H5RB/ref=sr_1_24?keywords=88+gram+co2+adapter&qid=1679538561&sr=8-24
I am new here and new to CO2 pellet shooting and I have enjoyed reading this entire thread, even though I am reading it almost a year past its posting. My plan is to use teflon tape and a wrench to secure a Heyxire adapter to the 90g CO2 container of my Sig MPX to allow its removal after shooting for the day and store the MPX without the magazine. I would appreciate your thoughts and thank you in advance.
Old Aviator,
That’s not recommended.
BB
BB,
Thank you for your prompt reply but I don’t understand why my intention would seem unsafe. Removing the CO2 bottle and removing the magazine would seem to me to be the safest way possible to store the weapon between outings.
Bob
Bob,
All companies recommend that you exhaust your CO2 cartridges before removing them from the airgun.
Crosman once made a 1017 that had an adaptor that could be removed from the gun without gas loss. I can’t see how it’s possible to remove the cartridge from the MPX and then put the adaptor on it. And I don’t believe the adaptor will fit inside the airgun. If it will then you should be able to do it, but the last thing you want is a CO2 container that’s pierced and outside the airgun.
B B
BB,
I have owned this MPX for years but only took it out of the box recently.
I do not have an indoor shooting space and I hope to take advantage of whatever reasonably nice weather days we have until Spring to get outside and shoot. I do not, however, envision shooting for long enough periods of time to exhaust a 90g bottle of CO2, nor am I immediately willing to throw away the cost of the unused gas after S-L-O-W-L-Y unscrewing the CO2 bottle from the weapon.
I have yet to screw a gas cartridge into my MPX, nor have I received the Heyxire adaptor from Amazon. I’m just trying to plan a safe and economical way to enjoy shooting for short periods of time without breaking the bank or freezing anything up by leaving a cartridge in or removing it too quickly.
My plan makes two assumptions:
(1) It assumes that the adaptor penetrates the seal of the cartridge but then holds the pressure until the weapon seals and unseals with the adaptor; this is the only way I can see that a cartridge could be removed quickly and safely once penetrated. The Teflon tape and oil would be placed on the cartridge before the adaptor is placed with a wrench.
(2) It assumes that everything will fit within the spaces of the airgun and the hollow stock.
If either of my assumptions are incorrect and I can’t find a work-around I will have to return the adaptor to Amazon and re-think this whole thing.
Sorry for the long post but I wanted to assure you that I have attempted due diligence and value safety as well as economy.
Bob
I don’t own an MPX, but I have a Crosman 160 and one of its descendants,, the AR2078. Is there an adapter that replaces the 90g tank with a housing that holds two 12g CO² cartridges? That way you can decide if your shooting session will last for about 40-50 shots, you can use one fresh cart and one empty one or if you will take 100 shots, two new carts.
Umarex makes and P.A.I.R. sells this one for an 88 g CO² cart, perhaps there is one for your 90 g cart?
Thank you for your suggestion but it would not seem there is room within the hollow stock of the MPX for holding anything other than the intended cartridge. The original configuration also evidently helps with the weight/balance necessary to duplicate the feel of the powder-burning 9mm.
Bob
Then back to the issue of safe storage, if I am storing a CO2 gun with CO2 in it, like my collection of Crosman Mark I and II pistols, I put a trigger lock on them and then put them in a lockable drawer (or safe). The danger is if anything gets in the barrel, it can become a projectile if the gun accidentally discharges. So you want to prevent that danger. I also have an cylindrical oatmeal box filled with rubber mulch near my shooting table to safely and quietly shoot into. That would catch any pellet or projectile.
But the whole point of my proposal is to remove the possibility of any propulsion and to remove all pellets, essentially leaving the weapon as it was when it was delivered by UPS after I bought it.
Tom,
I leave two 12 gram Powerlets (with a dime between them) in my Crosman 400, but I don’t shoot it very often, so for that one CO2 air gun of mine, I just couldn’t say if it is a bad or OK thing. I have a 2-cart Cap’chur long gun, but it came to me as a leaker and need to reseal it/have it resealed.
I’ll be interested to read what you find with that system.
Incidentally, my 400 has never had a feeding failure if the pellets I am shooting are wadcutters or very shallow domes. It is a thumper with RWS Superdomes and Meisterkugelns. The doubled-up skirt of the .22 Superdomes might help. I’ve yet to try Premier Domed Ultra Heavies, but I should. They do look a lot like the Rifle Premium Round Noses.
Michael
Michael,
The plural of Meisterkugel (Master Round [ball/marble]) is: Meisterkugeln. “Meisterkugelns” is an Americanization and over doing it a bit on the MANY you might have ;^)
shootski
shootski,
I’m a grammarian of American English; therefore, German is a vast uncharted sea to me. :^) That confessed, no one knows everything about anything. Consequently, I make errors in English as well, just not as often. ;^) Thanks for the lesson.
Here is one for you, an example of a language’s grammar and usage not “playing nice.”
We all know what graffiti is. The singular form is “graffito.” But what constitues a graffito? A single statement of graffiti, such as the legendary “Clapton is God”? A single complete character within an example of graffiti such as “C”?
And then there is the common conflict between the grammatically correct and clarity. The example one of my professors illustrated this conflict with was:
You knock on someone’s door. They ask through the door, “Who’s there?” Do you respond, “It is I.” That is the correct. Or do you answer, “It’s me”? The latter is clearer and much more natural.
Thanks again for the language lesson. I like them very much.
Michael
When FM’s late cousin owned the 38T which he passed on, pretty sure he used to leave the “powerlet” in the revolver because it had to be ready for the almost-daily rat-shoots around the common area where he lived. Don’t recall if he used pellgun oil on the cartridges. Do not think he did. Yet seems that gun did not leak until the seals went bad years later, at least 10 years after he bought it.
FM was not so lucky; about a year plus after reseal, got a leaker even after following the “oil the powerlet” rule. Admit to not removing the powerlets until after they were empty. Thightening the ring that holds the piercing valve seal in place recently seemed to help, but after losing another cartridge found the ring was still not tight enough – if that is not the cure, maybe will give replacing that seal a shot (pun intended) or put it in Mr. Willnecker’s hands again. And hopefully learn from the experience. Gases for today’s words of wisdom, B.B.
Basil,
Yes, BB has gas today. But why do you ask? 😉
BB
Tom,
I have a LOT of CO2 air guns, most vintage, but still quite a few newer. I have no bulk-fill models, a handful of 88 gram models and a half dozen 8 gram cartridge models, but most by far use regular 12 gram Powerlets.
I have never taken the CO2 out of an air gun for storage (although I have a few times for shipping). With the 88 gram ones, I always apply Teflon tape in addition to the requisite Pellgunoil application. Never any leakers, even after years of storage. I have also never had a small capsule air gun leak after years of storage, unless it was a leaker to begin with. With CO2 slow leaking air guns I simply shoot uintil their is no more gas, remove the empty Powerlet, and then store it.
Incidentally, a while back I stopped putting a drop of Pellgunoil on the tip of each Powerlet and instead started putting four or five drops directly on the seal inside the air gun and then gently dropping the Powerlet into the gun.
I have always considered the rule to exhaust CO2 before storage a myth, because I have never experienced a problem with air guns I know to be non-leakers. Then again, there is always a first time, so I might get a rude awakening some day.
Michael
B.B. and Readership,
Great coverage of It Depends!
I’ll start with CO2 since it was the power source for some of my first adult airguns. I used Crosman Powerlets®/bottles at first but quickly converted as many of those to bulk fill as was possible. I bought two 20Lb Siphon tube equiped CO2 Cylinders and fill assembly. Many of the Dennis A. Quackenbush (DAQ) early airguns were CO2 powered to include the SSP and 2240 based guns. Dennis made a bulk fill conformal adapter/bottle that could be screwed into end of the 22XX tube in place of the Powerlet® and end cap. It made the .25 caliber guns and conversions able to shoot Diana .25 domes at the same MV as a stock 22XX.
http://quackenbushairguns.com/CrosmanPistolItems.htm For some historical information items are no longer being sold.
With an enlarged/flow improved valve in a 2250 tube you could get another 150 or so FPS. It avoided the dangerous route that some modders used of pressuring the thin Crosman tube!
Many changes started in the early 1990’s with hpa modifications of CO2 powerplants and dual fuel systems by the modders and then by the manufacturers; Benjamin Discovery being one of the biggest sellers. I still have two 20Lb cylinders currently mostly full and doubt I will ever run them to empty. They would need a Hydro Test before getting refilled no doubt.
As far as keeping CO2, Multi-pump, and PCP pressurized: My bulk fill CO2 guns are designed to always be FULL (by weight) and have never leaked down. My Multi-pump are always kept with 1or 2 pumps to keep the pump face and valve lubricated and sealed. I use Mac1 Secret Sauce to lubricate my single and multi-pump compression tubes and valves.
For PCPs I keep them fully pressurized in storage and use non petroleum Chamber lubricant; a drop or two into the Foster (fill port) fitting every few fills and always if filling for known longer periods of storage.
If you are worried about work hardening the metal it is the number of fill-empty cycles that are of concern and not pressurization to Rated Fill Pressure.
SAFETY concerns are Storage Dependent and can be solved with a simple trigger lock or in the case of a bolt gun with a Chamber Open Lock. A LOCKED Arms Room, Vault, Closet, Safe or Case are my methods of choice to keep my guns and other weapons out of the hands of the untrained and/or uninformed.
shootski