How to tune your air rifle – Johnathan Young explains the process

Tuning may have taken off in the 1970s, but is still relevant today and now includes CO2 and PCPs as well as springers, as Jonathan Young explains.

A spring and a tub of grease – now that’s tuning the old-fashioned way – and notice the properly finished ends on the mainspring

Some people like to tinker, fixing things when they break. But sometimes things don’t even have to be broken, and that’s the case with tuning, a process that really came into its own with spring-powered rifles back in the 1970s, mainly because those are the type of rifles most of us had at the time.

The aim is to improve performance – not to make something unreliable or dangerous. At its very best, tuning may often decrease power, as an air rifle running high, but still within legal limits, may kick like a mule, making it difficult to control. 

This will be inaccurate, and tuning will smooth the gun’s performance, improving accuracy and the user’s confidence. We’ve all been there – shooting an airgun should have a grin factor rather than a big grimace. Being relaxed as you pull the trigger is vital for accuracy, whether it’s target shooting or serious vermin control.

Today, tuning kits are widely available, and thankfully here in the UK there is a knowledge base in tuning springers which goes back many years. Stripping out a modern springer is no different to an older Tracker or Airsporter. 

Polishing the internals and the piston, adding buttons to it so it rattles less as it shuttles down the cylinder tube can all make an airgun smoother and better to use. It’s definitely not about jamming a bigger and more powerful spring inside, that’s for sure.

A chronograph is a vital tool for all airgun shooters, not just tuners, as you need to ensure your airgun is running within the legal limit

Whilst tuning springers has been considered essential for decades, other airguns can benefit too. Most PCPs are spot on straight out of the box nowadays, but back in the early days air regulators were unheard of and the usable shot count was lower. Tuning the hammer release system could smooth things out though. 

Serious owners tested and noted the power curve for their guns, revealing the so-called sweet spot, a combination of the available air pressure and the number of shots available before both the pressure and the point of impact dropped. Owners would then simply refill their guns back to that optimum  pressure. With regulated valves most of this is now unnecessary. 

Today’s PCPs are usually fitted with anti-tamper valves by design, and with some rifles running near the legal limit this is a very sensible step.

Low-power CO2 airguns, especially air pistols, can sometimes benefit from tuning. On release, those heavy molecules bump around against each other and the interior of the airgun, losing energy. 

Tuning and free-flowing simply helps the gas move through the valve to the barrel with less friction. Stripping out a valve, polishing its internal walls and the valve stem removes minor manufacturing marks, burrs and flaws that catch and drag the gas. It might sound a bit like Elvis is alive and living on Mars, but it really does work. 

These Umarex and Baikal Makarov valve stems are tiny and show the type of parts that CO2 airgun tuners have to work with

It’s logical that anything will travel faster in a straight line, so some tunes involve removing valve metal and smoothing the internal edges – it’s a big thing in Crosman tuning circles.

Allowing more gas to escape quicker through the valve stem ports when the valve is knocked open continues the work. Ports are literally opened out and aftermarket valve stems are now available, for example some microscopic ultra-tuned stems for some air pistol designs.

Many of these minor tunes certainly add up when they are put together.  Remember that as with springers, “go faster” is not the same as “go better”. Gaining just a few more feet per second from a CO2 gun, for example, can at the very minimum mean using much more gas. Good tuning, however, allows better consistency between shots.

It wasn’t so long ago that most high-end target pistols used at international level were all CO2-fed. Some tunes take a different path, aiming to utilise every last molecule of gas to achieve a higher shot count with minimal shot deviation and possibly with only a slight reduction in velocity from standard. Impossible? No, it’s simply  good tuning.

CO2 is temperature-sensitive, and when tuning all CO2 airguns they should be tested extensively to ensure they don’t exceed the legal limit in the summer heat, with the inevitable acceptance that performance will then drop a little in colder weather. If you’re really desperate to go shooting on the darkest, coldest winter days then have a springer as a fallback.

The Makarov valve stem shows the three minuscule holes – just how did those engineers manage to achieve something as small as that?

Some air rifles like the Hammerli 850 Air Magnum are about as good as they can be out of the box, being designed to cope with seasonal temperature fluctuations whilst giving us accurate guns that are still within the law in the heat of high summer. With guns like these, tuning must take a back seat as there will be no improvement.

As I’ve already mentioned, tuning for consistency between each shot is much more important than maximum output. In the past, far too much emphasis has been placed on attaining power of the highest possible limit in respect of the current UK legal limits, which are six foot pounds for air pistols and 12 foot pounds for air rifles. 

These figures are in reality the maximum allowed, not figures to aim for. In tuning, no attempt should ever be made to try to reach that maximum. Tuning for consistency and smoothness, however, does mean an increase in accuracy.

The best advice anyone can receive is never attempt to tune or modify any airgun unless a chronograph is to hand. If none are available through a local club, friend or gun shop, any tuning work contemplated should be put on hold or even stopped dead. 

Tuning and modifying any airgun without checking it over a chrono is total muppetry, and could lead any owner to legal disaster.

But done properly, tuning brings so much personal satisfaction that it keeps many in their sheds and garages tinkering away for hours with their airguns. And that’s got to be a good thing! 


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Posted in Features, How to

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