While this article may seem a bit simplistic to many airgunners, you’d be surprised just how often the issue comes up. While consulting with a prominent airgun manufacture, I would often work with customers wanting to return their new PCP airguns because they were “leaking” or not able to be filled to the full 200 bar capacity. Nearly every time the issue was operator error and not the fault of the airgun, fill system, or air cylinder. We’ve touched on some of the products used to fill PCP airguns. In this article we’ll take a look at one product in particular, the Air Venturi G4 hand pump.
Looks just like a bike pump?
Looks can be very deceiving. While the G4 Hand pump may look like a traditional bicycle pump, it is very, very different. Your typical bicycle pump may reach up to 60 or even 100 psi, where the typical PCP hand pump can reach pressures up to 3300+ psi. In the case of the Air Venturi G4 hand pump it can pump to a maximum of 230 bar or 3335 PSI. With most PCP airguns requiring up to 200 bar, this hand pump is fully suited to the task at hand.
Most hand pumps come equipped with a standard 1/8 BSPP connector at the end of the fill hose. This is a standard size that’s compatible with most fill probes included with PCP airguns today. For this article we’ll be filling a Hatsan ATP-2 Tactical Carbine / Pistol. There’s a good reason for my choice. The cylinder is very small on this airgun which means I won’t have to pump nearly as much to fill it to the required 200 BAR! When it comes to filling larger PCP air rifles or PCP cylinders, the general rule of thumb is that it takes 10 or more pumps to boost the pressure by 100 PSI. The larger the air reservoir, the more pumps that are required and vice versa for smaller reservoirs.
Ready to “pump you up?” Not yet.
So we have our hand pump and our airgun. Let’s start pumping and get to some shooting! Well we’re not quite ready yet. We need to attach the bundled fill probe to our hand pump before we can start. Here’s where things can get interesting. There’s a percentage of folks that just hand tighten the probe into the end of the hose on the hand pump and then try and fill their airgun. These are the folks that wind up calling claiming the gun, pump, or cylinder is “leaking” and defective. Truthfully, this is not their fault. There’s not a lot of documentation, at least not that I’ve seen, that really spells out the “right” way to connect the probe and fill the airgun. So let’s address that now.
High pressure air is under, well, high pressure. Simply finger tightening any bundled probe or fitting into the end of the hose is NOT going to get it done. You’ll need to get some Teflon tape and wrenches to properly install probes and fittings to your fill system. Here’s how it works.
Tape and Tighten
Make sure that you have a clean workspace, some plumbers tape (Teflon tape), and the proper sized wrenches for the probe and the hose fitting. You may also choose to use a vice to hold the hose fitting and just a wrench for the probe. That’s up to you, either method works just fine. The first thing you want to do is apply a few layers of plumbers tape to the threads on the probe. Try and apply them so that they go “with” the probe when you tighten it into the fitting. This way it won’t try and bunch up on you and create gaps. If you get it wrong the first time, just remove it and reapply it in the right direction.
Go ahead and start installing the probe by finger tightening it as far as you can. Then, either using two wrenches or a vice and a wrench, continue to tighten the probe into the fitting until it’s pretty tight. You don’t want to over tighten but you need it tight enough that it’s not going to leak under pressure. If you are concerned with over tightening, don’t worry. If you get any leaking as you reach max pressure, just bleed the system, disconnect the probe from the air rifle or cylinder and tighten a bit more. Continue as necessary until you don’t have any more leaks. If need be, you can remove the probe and reapply Teflon tape, maybe a few more layers, and then reinstall the probe. It may take a while the first time, but once it’s properly installed, you should not get any more leaks.
Now, let’s pump you up!
With our probe properly installed into the hose fitting, it’s now time to fill or top off our cylinder. The first thing to remember is that this is not a race. Each stroke of the pump creates friction and heat that will degrade the internals of any PCP hand pump. Going fast just exacerbates the situation and can cause things to degrade sooner than they should. Even, smooth strokes are what you’re going for. For cylinders that require several hundred strokes to fill, refer to the product manual for appropriate rest intervals to let the pump rest and cool down so as to help prevent premature failing of the internal components. If the manual does not specify, a good rule of thumb would be 40 to 50 strokes and then take a break.
You can use the onboard nanometer to track your progress. When it reaches the correct pressure for your air rifle, you are done. To disconnect the pump you’ll need to first bleed the hose using the bleed screw at the base of the pump. Once the pressure is released you should be able to easily remove the probe from your airgun.
What if I want to fill more than just one gun?
For you all that have more than one PCP airgun, you may find that they all have different connectors. In Part 2 we’ll talk about what’s needed to make the Air Venturi G4 hand pump universal.