Buying a high-pressure air tank - Part 2
by B.B. Pelletier
Today's post is the thousandth since we began in March 2005. How fitting that it should come on Christmas Eve. Regardless of your religious views, we all owe Pyramyd Air thanks for their gift of this blog that has lasted so long. Let's hope we'll still be enjoying it after another thousand reports!
Although Abe asked for this report, I've heard from a lot of other readers who had questions and comments about air tanks. I'll try to address them all today.
Lloyd wants me to tell you that you should buy the largest scuba tank you can afford. He also says to tell the dive shop operator to please fill the tank to the max, because divers are less concerned with pressure than we are. His most important message, though, is to get to know the people at your dive shop. I couldn't agree more. I've seen airgunners ruin their entire PCP arrangement by simply alienating the dive shop personnel. And I've gotten many concessions and good treatment because I acted as though the dive shop was doing me a favor--WHICH IT IS. A little civility goes a long way when dealing with an owner/operator, like the guy who runs the dive shop.
Lloyd also asks if dive shops are the only place to get a 4500 psi fill. Well, I think they are the WORST place! I go to a paintball shop, because my dive shop fills me to only 4,000 psi or so. That's all his air system can produce. Sometimes, you can get a fill from the local fire station. It helps if the firefighters are also airgunners or maybe you take them a couple dozen donuts when you go there. Like I said, some guys can do it and others can't. Ask yourself, "What would Wayne do?" when you go, and you'll probably get what you want.
Jony wants me to remind you that a smaller tank at higher pressure is often better than a large tank at lower pressure. The proof of that is the fact that a 2,200 psi tank won't even give you one fill of your AirForce Talon SS, despite being just as physically large as an 80 cubic foot aluminum tank that gets pressurized to 3,000 psi. In this game, pressure is king, and we either want tanks at higher pressure or guns that shoot at lower pressure. Having both is the best of all.
A pony tank is a small air tank that divers and rescue workers use for convenience or for emergencies. We used them in the Army when fording rivers in our M60A1 battle tanks, because some of the crew members in the tank were 10 feet under water when the tank was driving across the river bed. If the air snorkel tube collapsed at those times, the driver could drown before he could get out of the tank. So, he used a pony air tank for a five-minute emergency air supply.
Big bore hunters carry carbon-fiber pony tanks to top off their rifles during a hunt. A small tank that fits in a backpack can refill even a large big bore rifle 2-3 times for a total of 6 additional shots. Any big-bore hunter will tell you that six shots is probably more than a day's supply for big-game.
When I competed in field target, I carried a 13-cubic foot pony tank to top off my Daystate Harrier. That rifle, which filled to 2,650 psi, got three refills from that little 3,000 psi pony tank. Since each fill was good for 24 shots, that was enough for almost 100 shots if you factor in the initial fill. A match typically has only 60 shots, so I was covered.
The Benjamin air tank is an example of a pony tank. Because it works on the Benjamin Discovery rifle which operates at 2,000 psi, it still gives plenty of fills.
Pony tanks have their place in PCP guns, but you don't want to buy one as your principal source of air.
Mr. B. says a day in the woods requires more shots than a Talon SS air tank can offer (maybe 35-45 shots at full power, depending on the range). Well, Mr. B., that Talon SS tank is actually a pony tank! Why not buy an extra AirForce standard tank? When your first one runs dry, just screw on a new one? That's how AirForce designed the gun to begin with.
Filling a gun from a tank
Abe asks about the proper way to fill a gun from a scuba tank, and I've had several other people ask the same thing. Here's a report I did on that subject. The first step is to connect the scuba tank to the gun. For this you need a fill adapter. One end connects to the scuba tank, the other connects to the gun. Both have to fit what they connect to, so you have to determine what it takes to do that. Scuba tanks and carbon fiber tanks have all kinds of valves. The most common scuba tank valve in the U.S. in the K-valve, but a DIN valve will sometimes be encountered. When the rated tank pressure goes above 3,000 psi, the DIN valve becomes more common. Your job is to determine what kind of valve your air tank has.
The K-valve is flat with an o-ring to seal it. This type needs a clamp that fits around the back of the valve to hold it.
A DIN valve has a hole with threads to accept any devices. This is the deeper 300-bar DIN hole, though both have the same diameter and threads.
A refill clamp fits around the K-valve.
Abe also asked about the scuba tank inspection process. That's not a part of this report, but I covered it here and also here.
Sooner or later, it'll dawn on you that a used scuba tank would be cheaper than a new one. But what you don't know is that there's a very good reason for that. A scuba tank must pass a hydrostatic pressure test every five years. When they fail or when they get near the end of their useful life, they aren't worth buying. We had a reader who bought a used tank for $50, then had to spend $135 getting it back in shape. While that was a little extreme (he needed a new K-valve), a hydro and the other tests you need could easily cost $60. And you could wind up with a tank that fails its hydro, leaving you with nothing, because the testing facility will drill a hole in your tank to remove it from the market.
The best way to buy used is to buy from a dive shop you do business with. If there's a problem, they'll take care of you.