How To Fill An Air Gun Using a Cylinder

How to fill an airgun

If you haven’t charged a PCP air rifle before do not worry, charging a PCP rifle with air is not difficult but you do need to be careful if using a valve not fitted with a restrictor. Most modern valves now come with these but if they do not, it’s pretty easy to overfill a rifle which could cause it to break the receiver. This is something you don’t want to happen as it’ll go off with a bang. Now I’ve got your attention, hopefully you’ll take care. Ideally get someone to show you how to do it until you’re confident, but when the time comes that you need to charge it yourself, here’s what you need to do.

1. When you first get your bottle you’ll need to attach the adaptor that came with the rifle to the end of the hose. It needs to be airtight but generally they only need to be tightened a bit more than hand tight. Be careful though as they’re fine threads, often in brass and if you overdo it, you could damage the thread. Once it’s on, leave it there. If you do have different guns, with various adaptors you can purchase a Best Fittings quick snap connector that can be used to quickly change the adaptor.
2. Ensure the adaptor is on the bottle and is hand tight. There’s an ‘O’ ring on the bottle end that only needs to be hand tight to seal.
3. Tighten the bleed valve.
4. Check what pressure your rifle is designed to take and don’t exceed it (on non-regulated rifles it’s better to under fill by about 10 bar just to be safe).
5. Attach the adaptor to the rifle making sure that both the adaptor and rifle valve are clean and dry. Make sure it’s fully engaged and never use oil or grease on any part of the filler or adaptor.
6. You’re now ready to start filling. Make sure that the rifle is somewhere it can’t fall over and use both hands to open the valve. As soon as it opens, close it off again quickly but gently. This stops you from venting 300 bar into a rifle designed to hold 180. It should now be much easier to open the valve and control the flow of air, once you’ve broken the initial seal and open it just enough for the needle to start moving on the adaptor gauge. Try not to rely on the one in the rifle, they’re not very accurate and are very slow to move, lagging a bit behind the actual pressure. Aim to fill slowly, the process should take between 30 seconds and a minute. Don’t be tempted to give it a quick blast at full pressure. You’ll notice that the pressure rises quite quickly until it equalises with the air inside the rifle and then it slows as the rifle valve opens to receive air. Keep it going nice and slow until you reach your intended pressure.
7. If you fill too quickly the compressed tends to air warm up as it transfers through the smallbore fill-hose.  This warmer air occupies a greater volume, indicating a higher pressure, making the gun temporarily appear more full than it actually is.  Once it’s allowed to cool for a few minutes from a rapid fill, the pressure will drop, leaving you less of an available shot-count before your next fill is due.
8. Close the bottle valve firmly.
9. Unscrew the vent valve and it will expel a blast of air. This allows the pressure to escape from the hose, so that when you remove the adaptor, it doesn’t fly off at speed.
10. Uncouple the adaptor
11. Take care and have fun shooting your charged air rifle