> It appears that the "TUNING" bug has bit airgunners real hard! But what bugs me is that it's often associated with "INCREASING THE POWER / VELOCITY" of the air gun without the slightest concern for "ACCURACY"!!!
> I came across this wonderful article written by one of the leading 'air gun tuners' which I want to share with those interested in knowing a little more about it. here goes.....
WHY TUNE A SPRINGER?
I'm often asked, "Why should I get my gun tuned?" There are many reasons you would want to get your rifle tuned. Often I'm asked, "WHAT IS A TUNE". Most of the time it's that the person calling wants to be sure about what they are spending their money on and will it be worth it. Consider this - R&D time, lathes, milling machines, honing equipment and tooling, raw material stock, mill and lathe tooling, stock working equip. etc. etc... All that coupled with the amount of time machining and fitting parts to your gun takes a lot of time and effort.
TUNING HELPS THE GUN LASTS LONGER
Every gun on the market is mass produced and has some weak links that could stand some improvement. While some gun makers use good quality springs others compromise to cut costs because "power hungry air-gunners" want cheap power. A good bit of people feel that springers are only designed to operate at 12ftlbs or they won’t last. That said, when I tune a gun I can often get 70-80fps more than a factory gun that was already hot and in so doing make the gun last ten times longer than even the same gun’s 12ftlb counterpart. The springs and seals I install will outlast the factory springs and give vastly improved performance.
Proper lubrication is a key element in a gun lasting longer too. Too much lube in the compression chamber will burn seals and cause dieseling that will shorten the life of the spring or the wrong kind of lube will cause piston galling. Making sure the rifle is sealing correctly is the single biggest improvement that can be done to a spring rifle. A spring guns ability to seal correctly is more important than any other single factor. It's the heart and soul of how a spring rifle gets the job done. It is by far the single most important issue when doing a tune and the most expensive to do correctly. Selecting the right spring, seal and lube mean nothing if the compression tube, does not conform to specifications. This is why correcting out of round or tapered compression tube inside diameters will do wonders for longevity. In a rifle with a suspect tube, honing the receiver with a precision hone eliminates this problem. In every rifle that I corrected the receiver I've seen improvement in its ability to shoot at higher velocity and be able to keep that velocity over a long period of time.
PERFORMANCE!!
A tune can affect several areas of performance and not every gun is the same in responding to a given combination of parts. Some guns respond well to bringing the power down but other guns have lots of potential for increased power while keeping the gun very pleasant to fire. If a gun doesn't respond well to jacking the power up, it’s not worth going into it no matter how bad you want it. I just don't want my name associated with that kind of work. Some guns do respond well to power increases but some miserably fail on accuracy. The power a rifle is able to produce is most often severely limited by the tolerances of the receiver. On rifles with suspect receivers often putting in a more powerful spring will yield lower power not more. This has been one of the biggest problems to face tuners who can only replace parts and not correct the underlying issues plaguing the rifle. Often they search for the magic spring or seal that will not resolve the issue.
It depends on the design of the gun and the tolerances of the receiver more than anything else. Some guns will not shoot smoothly no matter what you do if the receiver isn't corrected or the basic design isn't suitable for the power you're trying to achieve. Oversized transfer ports, inside diameter of the barrel being oversized, or too loose a pellet fit can cause heavy recoil as well. Sometimes a gun with a barrel problem can't be tuned smoothly until the owner is willing to opt for a new barrel. Some guns are tight in the breech and open up only to have the choke slow the pellet down before exiting the barrel.
VIBRATION: TWAAAAANNGGGG!
It’s the noise the spring makes after the gun has fired. This is not recoil as some keep alluding to. It's the noise and buzz you feel during and after the gun has fired. It is about 60-70% of the noise a spring gun makes. It's also the single most noticeable improvement when tuning a rifle. Eliminating vibration is a bye product of everything being precisely fitted in the rifle. Getting rid of or reducing vibration will reap you many benefits. One of the biggest improvements in reducing vibration is that your stock screws tend to stay put. If your stock is soft, wood can compress under the head of the screw due to recoil but most often I've found that reducing vibration with properly machined guides will just about solve this problem. Besides, that smooth solid THUNK the gun makes without vibration just makes it feel better.
SMOOTHNESS & ACCURACY
Bottom line is less recoil that is straight back and tighter velocity spreads will give better accuracy. 15-20fps speed is acceptable and won't affect accuracy much. Most of the guns I've tuned will get about a 3-10fps spread. The exceptions are guns with loose fitting pellets due to oversized bores, inconsistent weight and dimension of pellets. They also tend to leak air and get low velocity. I have always tended to think smooth meant little to no noise when cocking, no vibration and muted recoil, like riding in a new car.
THE TUNING PROCESS
The rifle is disassembled and cleaned out thoroughly. The receiver from your rifle has the cocking slot precision milled to be absolutely true and smooth and the receiver’s inside diameter it trued for its entire length on a precision honing machine. It is then de-burred to remove all sharp edges. A new spring is selected for your gun depending on several things like the desired power and caliber or even the pellet to be used or something like the general use of the gun (i.e.. hunting, plinking or target). Spring guides are made from steel, bronze or the finest synthetics (delrin) available. They are fitted to the individual spring to be used to eliminate vibration and control recoil characteristics. A better designed seal is used to often give higher power and tighten velocity spreads. Sometimes they are designed to smooth the firing cycle or last longer as well. The seal is always replaced with a new one. Your old seal will never be reinstalled in your gun.
The trigger is disassembled and de-burred. The sear rivets or pins are replaced with tool steel rivets on HW trigger units and the sears themselves are checked for hardness. If the sears are soft or some of the case hardening is thin they are either kiln hardened "through hardened" and tempered or case hardened depending on which sear or catch it is. The gun is then reassembled using several different lubes depending on the where they are going to be used and the material the guides are made of. One type of moly is used for pressure points, while another is used for the compression chamber and piston seal. Another lube is used on the receiver walls where the compression tube or piston slides. The trigger is lubed with special oils as well. All this takes a good bit of time to do right. For the effort put into it, the money spent isn't very much.
Tuning is best performed on a rifle that you want to keep and enjoy a smooth & accurate shooting. Sheer power isn’t worth the trouble to tune, if your gun is not accurate.
Paul Watts
Cheers
Briha
Thank you for the article, Brihji.
