They certainly provide plenty of fizzing fun, but are there ways to keep a CO2-powered airgun pistol on song? Phil Bulmer takes you through the basics...
Bubbly CO2 gas has opened up loads of new opportunities for shooters. It offers recoilless performance and a fair few shots from a single 12gr bulb, which is great for those who don’t or won’t want to manually pump up a rifle, nor fuss with scuba gear. It’s cheap to run, in the short term, with no outlay on expensive air tanks - though after a few hundred 12-gramme sparklets at 50p or so apiece, the air system starts breaking even. Still horses for courses though. Stripping a CO2 gun isn’t quite as generic as a spring rifle since every one I’ve ever stripped has had some quirk of its own. Some guns, like the Crosmans, are quite easy to take apart while the Umarex CP88, on the other hand, is complicated by the fact that it comes apart one way and goes back another. Many CO2 guns are more complex than spring piston guns, not least because they often have to perform tasks such as rotate a magazine, operate a hammer in double action mode and some even blowback and re-cock themselves. But there are still basics that apply so it’s not too daunting to strip one. If you’re are thinking of taking your gun apart though, just pause and consider a little diagnostic work before you crack on with the screwdriver. Should this solve the problem, as it more than likely will, then great. If not, options open to you will obviously include stripping the gun – though if you fancy the challenge, try to get hold of a parts diagram, which can be vital in the event of a ‘plastic bag’ job. For the uninitiated, a plastic bag job is when you quite sensibly open up the gun inside a plastic bag. When the two halves of the gun come apart, it’s not unknown for bits to shoot out like a metallic firework display – and the plastic bag collects all the bits. It’s then a Chinese puzzle trying to figure out where they all go, but at least they’re not all over the floor. Assuming, on the other hand, that you manage to get the gun apart with the bits staying in place, a digital camera is good for recording the dismantling stages, and the arrangement of tricky components. Perhaps one of the best options for repairing a CO2 gun is to take it to a gunshop who will usually have a technical bod who has all the spares on tap and can fix the gun quickly, or send it back to the manufacturer or distributor for them to do the work. Yes, you can expect a modest bill but it’s probably cheaper than scattering bits across the shed, not knowing where they go anyway and buying a set of seals only to find they’re the wrong ones…. If the gun is of the type with a CO2 sparklet bulb in the grip, you’ll probably find that the most common cause of the gun leaking will be the seal between the head of the bulb and the valve. Unlike firearms, CO2-powered guns actually cool down during rapid fire – and the more rapid the fire the more dramatic the cooling. The problem, long term, for this is that cooling leads to condensation and condensation can lead to rust which not only messes up the surface finish, it can cause seals to fail. In this case, more often than not, the seal can simply be winkled out and replaced, but prevention is better than cure. Wipe any obvious condensation away and allow the remainder to evaporate in a warm environment, then wipe over again with an oily cloth. Inside the cylinder compartment a whiff of silicone oil will leave a protective film and a tiny drop of the oil on the head of each fresh capsule will carry the lube up into the valve seal area. As I said, prevention is better than cure, and an excellent way to prevent such problems is to use up all the CO2 in the bulb and remove it, especially if you don’t expect to use the pistol again for a while. Seals have a habit of absorbing the carbon dioxide gas and it doesn’t do them much good, tending to make them too brittle, perished or a combi-nation of the two. Having said that, at least one eminent expert on the older Crosmans suggests leaving the gun charged, as it helps keep the seals in good condition! Most pistols have some form of overcentre type lever, designed to push the bulb against a puncturing pin to release the gas and keep the container hard against the seal. The lever is usually adjustable, with a brass thumbwheel or similar, and as that initial seal from bulb to gun flattens over time, shooters tighten up the wheel to try and get a gas-tight fit, the net result being more stress on the frame of the gun. I’ve seen at least three models suffering from this problem and one had managed to bend the frame so much that the hammer had jammed. Another area to avoid at all costs is in trying to convert CO2 guns to run on compressed air. To get the same amount of power from air as might be derived from CO2, the gun would have to be charged with air at a dangerously high pressure – all down to CO2 becoming liquid under pressure and turning to gas with a high expansion rate and other such witchcraft – so attempting such a conversion is both stupid, and probably illegal. Lubrication of seals is a debatable issue. Some say don’t use oil as it rots the seals whilst others say that modern butyl seals are fully oil-resistant and won’t suffer from any attack. These are opinions from trade experts and respected engineers, yet the advice is entirely different. What do I do? I prefer to use a silicone spray on seals in CO2 guns and a whiff inside the cylinder, to prevent rust, but never allow it near metal-to-metal moving parts as it’s guaranteed to seize things up. Another word of caution, this time relating to the CO2 bulbs themselves. There are very occasional instances when the seal on a newly installed bulb gives way, big style. The punctured bulb then dumps all its CO2 in a few seconds and this rapid depressurisation makes the bulb very cold indeed, so it’s best not to handle anything until the ice has melted, to avoid the risk of localised frostbite on your fingers. Mind you, it doesn’t half look impressive when it blows!