SO Why Tune my Stealth?

I'm an unashamed Ex-Military Techie and, when I saw my first Stealth I just had to have one. Its astonishing good looks, Militaristic simplicity and light weight immediately put it on my 'must have' list. When I took delivery of my UK specification 12" Stealth 2000 a week or so later, however, I quickly found that its performance didn't quite live up to its potential - and I set out to find out why. I bench stripped that rifle down to every nut and bolt and examined, measured tested and experimented.

My early work in the Spring of 2000 led me to a few simple conclusions:

 

  • The Stealth range of Rifles employs a highly efficient air system that can easily produce quite stunning power levels without wasting air or losing accuracy. It is simple, robust and reliable – sheer genius! However, the excellent rifle design appears to have been conceived in America and with a somewhat higher velocity than the UK legal 12fpe in mind.

  • The mechanism in the UK rifles appears to have been ‘throttled back’ in order to reduce power for the restricted British market. This has led to some compromisation of the original design and thrown up a few problems in the process - just for good measure!

  • The Hammer seems to be somewhat lightweight for the job intended, that of reliably striking the valve with the same force every time. It has been found that the plastic Hammer can chatter in a dry rifle and thus bleed off a substantial amount of its energy before it reaches the firing valve.

  • The Hammer spring seems to be rather weak for reliably propelling the Hammer into the valve in a consistent manner and exacerbates the problem above.

  • The firing valve return spring, which is fitted inside the valve assembly and inside the air reservoir, is, for some reason, of very heavy gauge wire. It is difficult to see why this is necessary when its primary function is simply to hold the valve shut in an empty reservoir prior to filling. Once filled, the air pressure, at nearly 3000psi, is more than adequate to shut the valve with remarkable alacrity!

  • This means that the Hammer, in order to open the firing valve, has to overcome its own sliding friction, its own inertia, the inertia of the Breech Slide, the friction of the front Breech Slide ‘O’ ring on the barrel, the air pressure inside the reservoir and also overcome the massively heavy valve spring before any valve movement can take place.

  • On many UK Stealth Rifles therefore, by the time the Hammer has reached the point of actually opening the air valve, a substantial amount of its initial energy has already been dissipated, often in a variable manner. As a result, valve strike varies from shot to shot and velocity consistency suffers with a resultant effect on accuracy.

Some of these problems can be minimised by careful setting-up, scrupulous cleaning and good lubrication and many Stealths are stunningly accurate ‘out of the box’. The fact remains however, that with a few well-chosen modifications, the Rifle can be transformed and the 'problems' virtually eliminated. 

If a UK Firearms certificate is applied for, then this Rifle can be unharnessed and allowed to develop the enormous potential for which it was obviously designed. However, even at 12 foot pounds (the UK legal limit for an unlicensed Air Rifle) the Stealth can me made into a smooth, sweet-shooting, accurate machine that will hold its own on any target range while allowing the efficient control of pests such as Rabbits, Rats and Corvids at ranges right out to 50 meters and even beyond.

................So why tinker with a reasonably acceptable piece of kit if mine's OK?

Leaving aside the obvious benefits of having a rifle that works more efficiently, more accurately and more reliably, there is the added benefit to the home gunsmith of learning how and why their rifle works. 

Left: Some guys even have Walnut Grips!    

Once the basic operation has been ascertained and the rifle’s mechanism worked through and understood, future malfunctions lose their horror and become minor annoyances to be fixed in minutes rather than fretted over and paid dearly for. Understanding WHY your rifle works helps you to shoot better, cleaner and safer ...... and there's nobody more popular down the range clubhouse than the guy who knows how to fix rifles - well!

 

I sincerely hope you enjoy this web site - my intention is simply to share my technical experience with this superb Air Rifle with other owners in the hope that they too will discover the attractions of going 'Off Road' in their choice of weapon and carrying out their own repairs and tuning work. There are plenty of horror stories of people who claim to have had awful problems with their Stealths - and who've quickly ditched them in favour of something a little more - shall we say - conventional? There are an equal, if not greater, number who now wouldn't own anything else! Strangely, many of these latter folks know a heck of a lot about their Rifle, why it works, how to fix it and how to shoot it well. In the words of our Transatlantic Cousins, "Go Figure!"

 


Best Regards
Bob Craske
February 2000

 

 

Above: Some of the Dutch Tuners have taken this art, with their +30" Daniel Lilja-barrelled
Stealths, to extraordinary levels and are acknowledged experts in modifying this rifle.