Back in the
early 80’s, I was at the local rod and gun club range in Ft. Walton Beach
Florida doing a little silhouette practice when a fellow showed up with
one of the then new RWS Model 45 spring-piston air rifles. The Model 45
was the first air rifle to claim 1000 fps. I noticed he had a very nice
(read expensive) scope mounted on the gun.
I just went about my business, but
after about 15 minutes I heard this fellow swearing and cursing about how
his new expensive airgun wouldn’t shoot no matter how carefully he held on
the target. “Maybe it’s the scope” I offered. “It can’t be the scope” he
replied. “It’s top of the line model, and it’s practically new. Besides,
I use it on my 30-06 and it works fine.” “It’s not an air gun scope?”
“No, why should I buy another scope for my air gun when I can use this
one?” At that point he picked the gun up in disgust and rapidly swung it
around to put it in his gun case. As he did so, a sound like glass
rattling around inside a tin can could be clearly heard. “Hear that?” I
asked. “Yah, what is it” he asked with a puzzled look. “That’s your
scope’s guts.” The poor fellow didn’t realize that powerful spring piston
airguns could rip apart an ordinary rifle scope.
To understand what was going on, we
need to examine some basics about recoil and spring-piston air guns. First
of all, it’s hard to imagine that an airgun would have any recoil at all.
As we all know, with normal firearms recoil is generated by the bullet and
gases exiting the muzzle. As you increase the weight and speed of the
bullet and the speed and volume of the gases, recoil will increase. The
only thing mitigating the recoil generated is the weight of the
firearm. Heavier guns recoil less than light guns all other things being
equal. All recoil is generated to the rear.
On an airgun, a typical pellet will
weigh only a minuscule 7.9 grains, and velocities are usually well below
900 fps on most rifles, and less than 500 fps on pistols. Spring-piston
rifles and pistols are complicated, heavy mechanisms and consequently
often weigh as much as a normal firearm, or more. For instance, my two RWS
air rifles weigh 8, and 8.2 pounds each. Therefore you could reasonable
expect the recoil generated in them should be absolutely negligible. With
that in mind, how was it possible then for that fellow’s first
quality rifle scope to be ripped apart?
Well there are a couple of things
happening here. First we have to realize that unlike regular firearms,
99.9999% of spring-piston recoil is NOT generated by the pellet and
the air being expelled out of the muzzle. It’s actually being generated by
the piston and spring, both of which are very heavy components, especially
the large steel spring. When the sear is released, the highly compressed
heavy spring will jump forward with tremendous force pushing the piston
ahead of it. As the spring and piston are moving forward, the gun is
recoiling back against your shoulder with significant pressure. Now here’s
the part that many people don’t understand. As the piston comes to the end
of the compression chamber it will actually strike the wall with
substantial force, and the gun will now bounce forward, recoiling away
So the essential elements to be
remembered here are that recoil from a spring-piston air gun is not light
but actually fairly considerable, and that there are two recoil pulses in
opposite directions i.e. one to the rear and one forward. For a scope to
withstand the recoil pulse away from the shooter, it has to be constructed
specifically for that task. Most scopes of that period were not.
Ok, other than being constructed
specifically to withstand a forward and rearward recoil pulse, what else
distinguishes an air gun scope from a normal rifle scope? Actually the
most important characteristic of an air gun scope these days is its
ability to focus down to 10 meters parallax free. Ten meters is the
standard distance that most air gun competitions are held.
The key word here is parallax free. So
what is parallax? As I explained in my series of articles on hand gun
scopes earlier this last year, parallax is an optical condition in which
the optical plane of the image and the optical plane of the crosshairs are
not the same. The effect is that any little head movement on your part
while looking through the scope will cause the apparent location of the target to move. In other words, when your head is in one location the
target will appear to be in one place in relationship with the crosshairs,
and if you move your head slightly, it will move to another location. On
some poorly designed or constructed scopes the movement can easily be 18
Rifle scopes without an adjustable
objective lens on the front are engineered to be parallax free at 100
yards. When used at distances shorter or farther away than 100 yards,
parallax will be introduced onto the image to some degree depending on the
distance to the object being viewed.
While some parallax induced target
displacement is not a big deal when hunting most larger game, it is a very
big deal when shooting groups, prairie dogs, or air gun silhouette
targets, especially when standing. Even a single inch of parallax
displacement caused by a slight shift in the position of your head or the
position of the scope in relation to your head, can mean the difference
between a hit or a miss on the tiny air silhouette targets - particularly
Well what about rifle scopes with an
adjustable objective lens? Won’t that take care of the problem? The
typical such scope will only adjust down to 50 yards. This means that they
can’t focus or correct parallax closer than that distance. Obviously
being able to focus down to 50 yards doesn’t help us if we want to shoot
at 10 meters.
To summarize then, an air gun scope has been traditionally defined as one
with special construction features to handle the double recoil of a
spring-piston airgun and which has also been designed for parallax free
viewing at 10 meters. The answer in two out of three cases is our
old friend parallax. Neither the adjustable objective, or non-adjustable
objective Leupold or Burris rifle scopes will adjust down to ten meters.
However, their specialized air gun scopes can. So even though all of their rifle
scopes are mechanically capable of being used on spring-piston air guns, their
optical systems aren't.
Additionally, there are also plenty of
casual air gun scope users out there that prefer fixed power scopes with
non-adjustable objective lenses. Hence, the manufacturers build special air gun
scopes for that market.
Now Bushnell is a different story. With the
exception of two of their “economy” products, every one of their adjustable
objective rifle scopes are mechanically capable of being used on a spring-piston
air gun as well as being optically capable of providing parallax free viewing at
ten meters. It is the only major scope manufacturer that I know that does
this. This is absolutely amazing as it give the airgun customer a huge variety
of scopes they can choose from as well having the flexibility of being able to
mount their scope on either an airgun, or on to their favorite center fire
rifle, or even a silhouette handgun. I consider this to be a major advantage.
Hats off to Bushnell!
Another issue that often comes up when
discussing air and rifle scopes, is whether a specialized air gun scope (from
any manufacturer) can be used on a regular firearm, either rim fire or center
fire. If the air gun scope is equipped with an adjustable objective lens, in
almost every case it definitely will allow the shooter to adjust focus and
parallax from 10 meters out to infinity. Additionally, the robust construction
features of these scopes allow them to be used on most firearms as well.
Consequently I’ve successfully used my air gun scopes on both rim fire rifles
and pistols with perfect satisfaction. Additionally, I wouldn’t have any problem
using an airgun scope made by any of the big three on a center fire rifle
either. In fact I’ve done exactly that many times, using my Leupold 3 X 9 EFR
scope (Extended Focal Range) on everything from a 22 Hornet up to a
30-06. However, I would be reluctant to use an airgun scope from a third tier
manufacturer on a heavy recoiling firearm, although they would be probably fine
for a rimfire gun.
So getting back to the original question of
“what is the difference between a rifle scope and an air gun scope?” The answer
is “It really all depends on who the manufacturer is.” In the case of Bushnell
there is essentially no difference between the two types. In the case of Burris
and Leupold, there’s no difference in construction, but there is in optics. In
the case of other manufacturers like Weaver, and Simmons, there is a definite
difference in both construction and optics. For BSA, it’s a mixed bag. Some of
their rifle scopes are mechanically compatible with air gun shooting and some
aren't. However, none of their rifle scopes are optically compatible with air
gun shooting. With Tasco, two of their rifle scopes are both mechanically and
optically compatible with air gun shooting. They are the 8 X 40 X 56 Tactical
scope and the Mag 40 6 X24. Interestingly, this particular Mag 40 scope is sold
in the U.S. as a rifle scope and is sold in Europe as an airgun scope. The other
scopes in the Mag 40 line do not meet either of the requirements for air gun
shooting. Other Taco rifle scopes do meet the mechanical requirements but not
the optical while even still others will correct parallax at 10 meters but not
meet the mechanical requirements. You figure it out.
So you see it's a very confusing situation.
It’s enough to make your head hurt trying to figure out all these differences
between the various manufacturers and even within a given manufacturer's line
Last point. If you’re shooting a pneumatic
air gun, the necessity for unique construction features for spring air guns
becomes unimportant because there is no double recoil pulse. The main and only
thing you need to be concerned about then is parallax displacement at ten
meters. Fortunately there's plenty of high magnification rifle scopes around,
especially from Bushnell, that will correct parallax at 10 meters.
Moral of the story? Check those
specifications in the company's catalog or web site carefully before you buy a
scope for your airgun. If the specifications don't answer all your questions,
call the company's tech customer service line.