Why are some spring guns more sensitive than others?
by B.B. Pelletier
Let's look at a question posed by Dave on Friday.
"I was wondering why different spring guns need different holds. Is there really that much difference in how they are manufactured?"
Good question, and I like giving the answer, because it explains so much about airguns - and everything else!
Yes, there can be a lot of difference in how airguns are manufactured. There is also a huge difference in how they are designed, which also affects how hold-sensitive they may be. Before I get to that, let me tell you a short story that will illustrate my point.
Formula Vee racing
A friend of mine was into Formula Vee racing. That's a poor-man's Formula Three car powered by an air-cooled VW engine. Although I said "poor," it's easy to spend more than $50,000 on the engine and car - so it ain't cheap. Because the engines are small and low-powered, the speeds are slow, compared to Formula Three.
My friend built engines for these cars. His engines always performed a little better than all the others, which kept him in demand. His competitors wanted to know his secret, which he never told them but did share with me. When he built an engine, he kept the specifications as close to the limits as possible. He blueprinted the engines, which not only meant their tolerances were tight, but also all moving parts were balanced to the gram! When they revved, they were smoother than the engines of his competitors. They got up to speed a little sooner and revved a little higher than all the other engines. And, that, in the hands of a good driver, won races!
The same is true for airguns. A "1000 f.p.s." airgun that recoils and buzzes when it shoots will throw pellets all over the place compared to a smooth-shooting 900 f.p.s. rifle that feels like a safe door closing when it fires (yes, there are such rifles). But, power doesn't have to go down for performance to go up. A stock .22-caliber Beeman R1 gets about 17.5-19 foot-pounds of muzzle energy. It vibrates some and kicks a lot. When the legendary Venom Mag 80 Laza tune was applied, the power rose to 23 foot-pounds, while the vibration stopped completely and recoil dropped to the same level as a Beeman R7. A rifle with that tune would actually shoot better than a factory R1 - just because it was easier to shoot the gun. That's what can be done with a good tuneup.
Now, the manufacturer can also do this to the gun before it leaves the factory. That's exactly what John Whiscombe does with each of his handmade air rifles. They're in the highest state of tune when they leave the factory. All the hand work that goes into that tune drives up the retail price of the basic gun to $3,500! Wouldn't it be nice if someone would design a gun that could be built right without the need for all the hand work? Well, someone has!
Air Arms has designed a spring gun that goes together quickly and still delivers wonderful performance. It's the TX200 Mark III. Please don't write me to ask if the TX200 Hunting Carbine or the Pro-Sport are just as good as the regular TX200 Mark III, because I am telling you right now they aren't. The TX200 is perfection. The other two fall short - though not by a lot.
Other air rifles are compared to the TX200 both in terms of smoothness and insensitivity to hold. The HW77 and HW97 are pretty close. Both can be improved with tuning. There are other rifles with increasing sensitivity that are still considered not too sensitive. However, breakbarrels, as a design style, are always more sensitive than underlevers and sidelevers. They can be just as accurate as the others, but they nearly always do require a lot of special handling technique to shoot accurately. Just why this is, I really don't know.
Here's what I do know for certain.
1. The less a rifle recoils and vibrates, the less hold-sensitive it will be.
2. Rifles of the same model tend to be alike. If one Beeman R1 is hold-sensitive, they all are. Only by tuning can you make a difference in one specific rifle.
3. Rifles of similar build characteristics tend to perform similarly - which is why I don't have to test each and every model of Gamo to know how they perform. One time I got bitten by this generality, though, when I tried to estimate how the Gamo CF-X would perform. It surprised me by out-performing my estimate. In general, though, rifles of similar builds perform similarly.
So, Dave, there are lots of reasons why different spring guns perform differently. However, you now should know that they aren't all unique. There are ways of generalizing.