Jaron's Realm

Ask me the time, I'll tell you how to build a clock

Things I Wish I’d Known Then – Part 2

Posted by Eric on 04.12.09

Time to Think About Gas

Continued on from Part 1.  You’ve now got your most important piece of safety equipment, your mask.  Now you need to think about some more hardware.  Many people might think of getting a gun, or marker, first.  While you can go that way, I’d suggest some other gear first.  You need a good gas source to power your gun and some gas tanks aren’t compatible with some guns.   So let’s cover this first, shall we?

You don’t run a fine Lamborghini on basic unleaded.  And while it might help a little bit, filling your old Super Beetle with premium doesn’t change the fact you’re driving a Bug.  So before you get a shiny new gun, you better check what kind of “fuel” you have available in your area.  Paintball runs on two primary gas sources: carbon dioxide ( CO2, ) and high-pressure air ( HPA. )  The two work very differently and most guns can’t run on both.  CO2 is the most common used around the world so I’ll start with that.

Carbon Dioxide Gas

First, you need to know how CO2 works.  Carbon dioxide is actually stored as a liquid inside the tank.  This liquid evaporates very easily and that’s what provides the gas pressure to run a paintball gun.  In physics, this is called vapor pressure.  The warmer the CO2 is, the higher the vapor pressure.  At room temperature of 70 °F / 21 °C, the vapor pressure is around 850 psi.  The tank only holds a small amount of liquid CO2 with the rest of the volume taken up by gaseous CO2 that has evaporated and then pressurized to keep the rest of the liquid from evaporating.  When gas is released, the internal pressure drops which allows more liquid to evaporate, bringing the pressure back up.  However, as the liquid CO2 evaporates, it also cools down, just like you cool down when sweat evaporates off your skin.  As stated above, when it cools down, the pressure also goes down.  That means every time CO2 is used to fire a paintball, the pressure drops and the gas and liquid both cool down a bit.  Now individual shots alone won’t do much, but sustained heavy fire can actually cause frost to form on the outside of a CO2 tank.  Here’s a chart showing approximate vapor pressures at various temperatures.

Carbon Dioxide Temperature/Pressure Chart
Temp °C Temp °F Approx. Vapor Pressure
0 °C 32 °F 525 psi
5 °C 41 °F 590 psi
10 °C 50 °F 660 psi
15 °C 59 °F 740 psi
20 °C 68 °F 820 psi
25 °C 77 °F 900 psi
30 °C 86 °F 990 psi
35 °C 95 °F 1080 psi
40 °C 104 °F 1175 psi

This changing pressure is the biggest problem with CO2.  On a hot day, a CO2 tank can easily fluctuate 20 °F or more as it cools from use only to be warmed again by the sun.  Most guns that can operate on CO2 are affected greatly by the input pressure, particularly how fast they shoot a paintball.  As the pressure goes up and down, so does the muzzle velocity.  While having your muzzle velocity drop off, commonly called shoot down, is mostly just annoying, having the velocity spike can be downright dangerous.  Also, in rare occasions, it is possible to siphon liquid CO2 into the gun itself which can make it freeze up, damage internal components, or possibly throw it into full automatic fire.  Now, those are rare exceptions, but they can happen.  And because CO2 changes with temperature, it can be very difficult to use it in cold weather.  Another complaint some players have, though minor, is that you really don’t know how much CO2 you have left in the tank.  You can listen to the liquid sloshing around inside and make a guess on when it’s running low, but you can’t get an accurate guess of how many shots you have left in the tank before it goes dry.  But despite these problems, CO2 remains very popular for two big reasons: price and availability.

CO2 tanks are very inexpensive.  You can find a large 24 oz. CO2 tank for only $20.  CO2 tanks are marked by weight, indicating how much liquid CO2 can be safely stored inside, and common sizes include 9 oz , 12 oz, 16 oz, 20 oz, and 24 oz with heavier tanks providing more gas and more shots per fill. All CO2 tanks are aluminum ( at least I’ve never seen a fiber CO2 tank, ) which means they can take a serious beating without being damaged.  Since it’s just a tank and a pin valve, they also don’t need a lot of maintenance and they don’t have a lot of parts that can fail.  So long as you don’t lay a CO2 tank in direct sunlight ( remember, heat increases the pressure inside by a lot, ) it will survive just about anything.  When the tank is empty, refills are widely available, even in remote/rural areas.  Paintball fields and shops, industrial supply companies, Home Depot, possibly even the local Wal-Mart and Super Target will offer CO2 fills.

High Pressure Air

HPA is just what it sounds like.  It’s regular air stored in a tank at very high pressures, sometimes up to 5000 psi, though most tanks are either rated at 3000 psi and 4500 psi.  HPA is sometimes called nitro or N2 since some of the first HPA tanks held pressurized nitrogen gas, but they all work the same.  All HPA tanks have a pressure regulator in the nozzle which lowers the output pressure.  This means that regardless of how much pressure is inside the tank, air will only be released at the regulator’s setting, which is usually between 300 psi to 800 psi.  Some tank regulators are even adjustable so you can set them to your own preference.  This consistent output pressure makes HPA perform much better than CO2 in just about every way.  Generally speaking the regulator on the nozzle will keep the output pressure level regardless of weather conditions or shooting habits.  Indeed, many guns, particularly the “higher end” models, can only run on HPA.

So why, with these great benefits, would anyone not use HPA?  For one, HPA has a higher initial cost.  Even the smallest, cheapest tanks still hover around $50 new while larger tanks with better performing regulators can be close to $200.  And unfortunately you can’t just hook up an HPA tank to any old compressor to refill it.  They require specialized compressors that run thousands of dollars that not many stores have.  You’ll usually find HPA refills only at paintball stores, fields, and possibly a dive shop that fills SCUBA tanks ( though some shops won’t fill the tank if you’re not dive certified. )  You also might get lucky by checking at an industrial supply store or the local fire department.  If a store says they can’t fill paintball tanks, ask if it’s just because they don’t have the right air line adapter.  I worked out a deal with a SCUBA shop owner that if I bought the right fittings, he’d fill my tanks for free.

If you opt for HPA, you have a lot more options to choose from.  HPA tanks are usually labeled like xx/xxxx with the first number representing the tank’s volume in cubic inches ( CI ) while the second number indicates how much pressure can be safely stored in the tank ( as I said usually 3000 psi or 4500 psi. )  Keep in mind that large volume 3000 psi tanks won’t always have more air in them than smaller 4500 psi tanks.  Tanks rated at 3000 psi are the cheapest because they’re just basic aluminum pressure cylinders.  Tanks rated at 4500 psi will cost significantly more because they have to be much stronger and are made from aluminum sleeves wrapped in fiberglass and/or carbon fiber.  While these fiber tanks are a little lighter than pure metal tanks, the biggest benefit is that they can store a lot more air inside.  And you can still get a 4500 psi tank even if your area only offers refills up to 3000 psi.  While you may not be able to always fill it all the way, you also won’t need to upgrade your tank to take advantage of higher pressure fills at larger events or if the local store upgrades their compressors.

Selecting a Tank Size

Now it’s time to figure what size of tank you’ll need.  There really isn’t a right answer to that since it all depends on personal play style and what kind of games you attend.  It all comes down to how heavy a tank you’re willing to carry around and how many shots you want to get out of it before you need a refill.  So it’s usually helpful to play a few games with either rental or loaner gear before you get your own tank so you can get an idea of how many shots you use in a typical outing.  Here are a few questions to ask yourself.  What’s the refill situation like at the field where you play?  Are they cheap?  Included in field entry fees?  Free?  If so, you may be able to get by with a smaller, less expensive tank and just refill it throughout the day.  Or do you play outdoors?  Are there no refills at the field?  Do you just play pickup games with friends?  Or perhaps you want to go straight into larger scale scenario paintball games?  Then you might need a higher capacity tank to last through the day.

If you decide to go the CO2 route, you really only need to decide on a tank size. Since the price difference between sizes is only a few bucks, get the biggest tank you feel comfortable carrying around.  Or if you want to carry less weight while playing, get two smaller tanks and just swap them out as one starts to run dry.   Again, the cheap initial cost of CO2 can be very helpful for the beginner paintball player.

The HPA road has more options but will also cost more money up front.  You have to think volume and pressure, metal or fiber.  But like CO2, it’s not a bad idea to get the biggest tank you can reasonably afford ( and reasonably carry around. )  Keep in mind that a small 4500 psi tank may hold as much air, if not a little more, than a large volume 3000 psi tank, i.e. a 48 CI 4500 psi tank holds about the same air as a 72 CI 3000 psi tank.  Don’t feel like you need to break the bank here.  You can get a good tank for under $100.  Check around for used tanks that other players might be selling.  Search eBay, browse through the buy/sell/trade sections of Internet paintball forums, and check with local players that might be selling gear.  Winter is especially good for this since many players clear out their gear bag to get money for next year’s stuff.  As a beginning player, don’t worry too much about getting the highest performing tank regulator.  Chances are you won’t be using a gun that will benefit from it and you won’t be shooting faster than the regulator can fully recharge the pressure.  However, as a starting player, get a tank that has an output pressure of at least 800 psi.  This will ensure it works with just about any gun on the market ( I’ll go more into this when we cover guns. )

Add the Trimmings

A few extra questions and dollars with your tank can save you some headaches down the road.  First, if you’re buying a used tank, it’s important to check on its hydrostatic test date ( often just called hydro. )  Since pressure cylinders are only a few steps away from bombs, they need to be tested every few years to make sure they haven’t been damaged to the point they will fail and explosively decompress.  Hydrotester has all the details about which tanks need to be tested and how often.  Second, it’s a good idea to get a protective sleeve for it, especially fiber tanks.  Unlike pure metal tanks, either CO2 or HPA, fiber tanks are more susceptible to damage.  Don’t think they’re unsafe, but say you take a dive in a game and bounce your tank off a rock.  A metal tank might have some scratches or a light ding but otherwise will be perfectly fine.  It is possible, though unlikely, that a fiber tank can be scored, weakening the fibers.  A neoprene sleeve is only a couple bucks and well worth the extra protection.  Next, you can get protective caps, often called thread savers, that screw down on the tank nozzle.  You can also get caps for the fill nozzle on an HPA tank.  These will help protect the nozzle fittings from getting dinged up, or worse, getting debris in them.

Jaron’s Recommendation

After all this, I’m sure some people still won’t have an idea what to get.  To those people, I offer the following.  Personally, I use HPA and haven’t used CO2 for over five years.  HPA fills are readily available in my area and at the fields I play.  I like the better consistency it gives my shots and I use guns that can’t work on CO2.  If you have ready access to HPA refills, I highly recommend you get an HPA tank.  It opens up more options in what guns you can get in the future and lets you play better in more situations, mainly hot and cold weather.  But I realize that not everyone has access to HPA fills or maybe they never have to worry about cold weather.  If CO2 is your only option, then don’t hesitate in getting a CO2 tank.  If you’re wondering about tank size, I use a large 91/4500 HPA tank ( gets more shots than a 24 oz CO2 tank. )  Part of the reason is because I use a gun that isn’t as air efficient as others on the market so I go through more air than other players.  Second, I play in a lot of large scenario events where I need to be on the field for an hour or more at a time without being able to refill my tank.  And since I’m a bigger guy, the extra size and weight of the tank don’t bother me.  But I recognize such a large tank isn’t for most people.  If you’re in the HPA market and don’t know what size tank to get, I’d recommend two options.  One, if you’re a new player and haven’t decided whether you want to get seriously into the sport, I’d recommend a 47/3000 tank.  They’re fairly cheap so you don’t have to worry about making a big investment into a game you may not stick to.  But they’ll also be enough to let you play reliably and get a feel for the game while you decide whether you want to keep playing or not.  If you’ve already been playing a bit and feel like you want to keep playing for at least a few years, a 68/4500 fiber tank will work for just about anyone.  It’s a nice middle size that’s not too heavy but still has a good amount of air for most players, and you can find them under $100 used.  Even if your air needs grow, it’s still a great backup tank to have in your bag.  If you can’t spend quite that much, look at a 72/3000 aluminum tank.  They’re a little heavier and don’t have as much air, but you can find them new for $70.

Ok, so that sums it up for your gas source.  The next segment will deal with hoppers, loaders, and ( possibly ) guns, so check back next week.


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