High-pressure air doesn’t grow on trees. Nor does it fall from the sky. Sometimes you have to dive for it.
One of the challenges to using pre-charged pneumatic (PCP) airguns is figuring out where you’re going to get your air. That old bike pump in the garage won’t do it as it might only generate 100 pounds per square inch, give or take. When you need three or four thousand, you’ve got to upgrade the technology.
There are three basic options available to the modern air gunner.
First, you can buy a high-pressure hand pump. Depending on the rifle or pistol you use, this is a perfectly viable option. A few weeks back, we looked at two small-caliber PCP air rifles, the Umarex Gauntlet and the Gamo Urban 22. I deliberately used a hand pump when testing them out as part of the appeal of both models is that they’re great for entry-level PCP. Small caliber means less air, which means that you can fill them the manual way. Depending on the rifle, it may take 150 or so strokes with the hand pump to completely fill the tank. Oh, and I should note that as you get closer to full pressure, it takes some pretty aggressive muscle work to operate the pump. Let’s just say that I weigh a few more pounds than I did in high school and I found myself leaning on that hand pump with a lot of body weight towards the end.
Pre-filled Air Tanks
The second approach is to store high-pressure air in a SCUBA-like tank. The trick is to figure out how to get the tank filled in the first place. Those four-quarter air machines at the corner gas station won’t cut it, so you’re limited to professional air compression options like dive shops, paintball centers, and perhaps fire departments.
Finally, you can buy your own compressor – a smaller and more affordable version of what the businesses use. We’re going to go into these options in a future article, but for now, know that you can get one starting in the $600 to $2,500 range. They’re not cheap, but then again it powers your airguns for years.
Being disinclined to burn 15,750 calories using a hand pump for high-volume airgun shooting, I decided to check out one of the best high-pressure air tanks on the market. I borrowed an Omega Air Cylinder from the kind folks at Airguns of Arizona not only for rifle testing but to do some local experimentation on the best places to get gas. No, while always a leading contender, the answer isn’t Waffle House.
This tank is a 75 cubic-foot model, made from carbon fiber to handle the massive 4,500 pounds per square inch rated pressure. The cylinder includes an oil-filled pressure gauge that’s large and easy to read with markings for both bar and psi scales. The valve includes a female DIN (think large threaded connection) for filling, so it not only handles the pressure but is widely compatible. The valve itself is controlled by a SCUBA tank-like hand knob that’s easy to operate and control the rate of air flow. That allows you to safely fill your guns to the correct level with minimal risk of “too much, too fast.” Also included is a one-meter long hose with a 1/8-inch BSPP fitting with a Foster quick disconnect. That means it’s compatible with just about anything. Oh, there’s a pressure release valve to bleed the air from the hose when you’re done filling. All in all, this is a quality piece of gear.
So, now that I had the container, it was time to fill it up. I decided to start with local dive shops since there are two of them close to me.
I called the first dive shop to inquire about their carbon tank filling capabilities. Their bread and butter tank filling services can be a bit different than the requirements faced by air gunners. We’ll get more into those details in a minute. From information on their website, I found that the cost for an air charge ranges from $7 for an 80 cubic-foot tank up to $10.50 for a 120 cubic-foot tank. That sounded reasonable to me.
Anyway, a very friendly person there informed me that they would be more than happy to help me out, but that their compressor could only deliver about 4,000 pounds per square inch. Keep in mind, their customer base is divers who (according to my admittedly limited knowledge on swimming with Moray Eels and other scary sea creatures) need somewhere in the 3,000 pounds per square inch of air compression for those aluminum or steel tanks. New airgun tanks like the Omega Air Cylinder model I’m showing here, take 4,500 psi and sometimes more. That extra pressure juice gives a lot more fills not to mention having enough air pressure to fill the big, air-sucking rifles like the Gamo TC45 I’ve been working with recently. So, while I would get some use from a 4,000-psi tank fill, I’d be forgoing a lot of refills without that extra 500 pounds of air pressure. Since dive shop number one had the will but not the way, I persisted and contacted another one in the area.
Dive shop number two had a monster air compression setup and filling to 4,500 pounds was, in theory, no problem. But there was a gotcha. Most dive tanks still use a yoke valve system to connect the fill hose or regulator during use. It’s worked well for Jacques Cousteau, and all of his third cousins twice removed, so it’s reliable and safe. However, it’s not designed for the highest of pressures, like the 4,500 pounds I wanted. It’s technically possible to connect an adapter to a yoke fill hose system to “convert” that to a DIN threaded connection like the one used on my Omega Air Cylinder tank, but you’re really not supposed to fill through that method beyond about 3,400 pounds per square inch.
So, dive shop number two had a monster compressor, but since they earn their living servicing divers and not air gunners, the only direct fill hose connections they had were the yoke style. After a quick talk about the nuances of all this, the friendly owner figured he ought to go ahead and add a DIN-type fill hose to his collection. Since his compressor wasn’t the limiting factor, it would then be perfectly safe to also fill 4,500 psi tanks.
What You Need to Know About Dive Shops
Question number one is to determine what type of fill hose connections they have available. Obviously, it’s important to make sure that what comes out of their compressor will connect directly to your tank. When the second dive shop acquires a DIN fill hose, I’ll be golden and can get 4,500 psi fills all day long. If your shop must use adapters from a yoke-style, you might find that their max pressure available is less than you need.
Once you can connect, the very next question is to determine their maximum fill pressure. I suspect most shops can go beyond 4,500, but it’s worth asking first.
Finally, I’ll offer up a tip that dive shop number two’s owner shared with me. He hasn’t rushed out to buy the right parts to fill carbon fiber airgun or paintball tanks in part because he’s had less than ideal experiences with us air gunning types. Apparently, many of the people using his services for fills tend to complain about having to pay the full six dollars even though they’re just topping off a tank, maybe taking it from 2,000 to 3,000 psi. Air is free; it’s the process we’re paying for, so consider that six bucks a cost of filling your tank. That’s how dive shops pay for that five-figure compressor in the back room. They ain’t cheap.
In a future column, we’ll share some tips and information about approaching your local firehouse to get compressed air. It can be done too with the right approach and equipment.