A Competition Ready TX-200

I’m thinning out the collection, and selling guns that I’m not shooting. Just sold is the Jim Maccari tuned Air Arms TX-200 I shot in competition for two years. This shoots about as well as a spring gun can- with carefully selected pellets, it’ll shoot well under a minute of angle all day long. I used cleaned, sized, and relubed Crosman Premier 7.9gr pellets in competition- cleaning helps get rid of the bits of lead flashing you sometimes find on pellets. For a while I also weighed pellets, but I fond the Crosmans FTs were so close it wasn’t worth it.

The TX-200 is still the gold standard for spring-powered FT guns. Add a decent 4-12x or better scope and you can start being competitive in local Field Target matches. Right out of the box it’s a great performer, and  you can add custom stocks and have tunes done to make a good gun even better. (This gun was subsequently sold to a neighbor who’s developed a recent interest in airguns in general, and Field Target in particular.  This should get him off to a good start.)

Pellet Lubes

If you read airgun catalogs and web sites, you’ll notice that there are a number of lubricants sold that are designed to be used directly on pellets. Do they work, and are they worth it? Yes, and maybe.

I used to lubricate pellets for field target matches- after carefully cleaning, sorting and sizing them. After all, in competition, often it’s the attention to tiny details that seperate first place from the rest. For field use and plinking, I don’t really see a need- although it’ll help there as well.

Lubricating seems to have a number of benificial effects. One, it pretects pellets from further oxidation. Two, it prevents the buildup of lead in a barrel- something that, even in very small amounts, might cause a change in shooting behavior. Three, it seems to increase velocity a little in some guns, which will flatten trajectory. And fourth, it helps prevent rust in barrels. This is more of a problem in pneumatic guns than in spring guns; in a spring gun, the air entering the barrel is very hot, and tends to vaporize any moisture that may be there. In a CO2 or PCP gun, the gas cools down rapidly from room temperature as it enters the barrel, chilling it, and causing any moisture in the air to condense.

For CO2 and PCP guns, just about any lubricant can be used so long as it doesn’t attack the rubber seals on the gun. I’ve seen things like STP and even WD40 recommended by some shooters. A favorite with the PCP shooters at my club was a light furniture wax! Spring guns are pickier; you must use a non-combustible lubricant. Any fuel in the chamber will ignite when the hot air coming from the combustion chamber hits it, causing unpredictable behavior and depositing carbon in the barrel.

Most of the non-flammable pellet lubes are silicones in a light solvent that quickly evaporates. Some shooters use products like 3M Scotchguard, which is pretty much the same thing, and is about a tenth the price of a product bottled and sold for airgun use.

Whatever lube you use, use it sparingly- a few drops is enough for a tin of pellets. If you can see it or smell it, you’re probably using too much.

Scopes for Airguns, part II: Optics

Shopping for a scope you’ll encounter a dizzying variety of optical choices- fixed, zoom, low power, 6x, 3-9×30, 8×56- how can you make sense of all this? Start by understanding the numbers and what they mean.

The first number- or number- indicate the magnification of a scope. Two numbers seperated by a dash mans that the scope is a zoom type, with variable magnification. The number on the other side of the ‘x’ is the size of the objective lens in millimeters. Thus a 2-7×32 scope has an adjustible magnification of from 2x to 7x- that is, objects look bewtween 2 and 7 times as large as they would when viewed with the naked eye- and the objective lens is 32mm in diameter. Magnification is certainly simple enough, but what does the size of the objective lens mean? How does that affect performance?

Basically, the larger the objective lens, the more light is gathered, and the brighter the image- but only up to a point. If you divide the objective lens diameter by the magnification, you get what’s called the exit pupil size- that is, the diameter of the bundle of light presented to your eye. The bigger the exit pupil, the brighter the image, until it equals the size of your eye’s pupil. Beyond that, there’s no benefit. So how big is you eye’s pupil?

It varies, depending on the brightness of the environment, and a person’s age. In bright sunlight, the pupil might contract to a 1-2mm or less; at night, a young person’s pupil might be anything from 5 to 9mm, with 7mm being around average. As we age, this decreases on the order of a millimeter or more over the course of one’s life.

Most shooting is done in daylight, and so a pupil size of more than 2-4mm is probably unecessary. Shooting around dusk- say, shooting vermin around a farm or garden- you might profitibly go as high as 7mm.

As you can see, the higher the magnification, the larger the objective lens size you need to acheive a given exit pupil. The old Beeman 2×15 SS2 scope looks tiny until you realize that it has a 7.5mm exit pupil; making it any larger would be a waste of glass. The popular 3-9×32 scopes marketed by many companies for airgun use has an exit pupil of only (32/9) = 3.5mm at maximum magnification; fine for daylight use, but too dim for use at dusk. At the other extreme, I saw a 3-9x80mm scope advertised in a British airgun shooting magazine as the ultimate night hunter- 80/9 = 8.88mm, far bigger than 99.99% of the pupils out there in the population.

Most of us need no bigger than a 4mm exit pupil for most uses, as we do most of our shooting in daylight, unlike our British cousins who sometimes hunt at night. But what about magnification? How much do you need? As always, it depends on the ranges you shoot at, and the targets you’re shooting at.

At the high end, Field Target shooters like to get as much magnification as possibkle, for two reasons- they’re shooting at some very small targets, and high magnification makes it easier to use your scope as a range finder. That’s critical in figuring out your trajectory. Most shooters seem to consider 6-18x to be a minimum range, with the use of 8-32x and 8-40x being not uncommon.
So why doesn’t everyone use a 8-40x scope? Cost is one reason, size another (they’re big!) and ease of use a third. It is extremely difficult to acquire a target at 40x- field target shooters typically acquire the target at a lower magnification, and then zoom to maximum and focus to find the range. Then they adjust their elevation and windage, and aquire the target yet again. Fine for shooting a steel target fastened to the ground, but not to good for game.

Hunters typically use lower power scopes, or even fixed scopes. I have a Burris 6x mini on my Theoben Sirocco. It’s small, very rugged, and quick and easy to use. It doens’t allow for the same precision when shooting at 55 yards as does my Simmons 6x18x scope, but I try to hunt at shorter distances than that. (A miss in Field Target means you lose a point; in hunting, it means you wound an animal, and as hunters, we should always try for quick, humane kills.) Scopes in the 2-7x and 3-9x are very popular, and indeed are probably ideal for hunting.
Plinkers, who shoot for the pure fun of it, have the widest range of choices. Some like big target scopes, others like small, simple scopes, and some like the non-magnifying scopes and optical sights commonly seen on competition handguns and combat rifles. These don’t allow the same precision in pellet placement as do magnifying scopes, but a good shooter can do well with them, and they’re the quickest and easiest to use of any sight system.

What about the leaf sights that come on just about every air rifle?  Why not just use them? Well, while they’re more than adequate for plinking, they simply don’t have the accuracy needed for airgun huting, let alone target. Sure, a lot of deer have been taken over the years with iron sights, but the lethal area on a deer- the heart and lungs- is much bigger than entire body of most of the animals airgun hunters pursue. There are always exceptions- I know of some very successful hunters who use an old Sheridan pump gun with the stock sights- but for most of us, a scope is a better choice.

Scopes for Airguns, part I: Construction and Parallax

If you’ve been shooting a while, you’ve probably heard that not all rifle scopes are designed to handle the two-way shock of a spring piston gun. Let’s see why that’s so.

If you look at the objective end of a telescope sight- the end that faces the target- you’ll see that the objective lens is held in place with a threaded retaining ring, often sealed with a drop of lacquer or other adhesive. What’s unseen, though, is how the lens is held on the other side, or how internal elements are held. Quite often lens elements in scopes are held in place by a simple raised ring, created by rolling a die around the tube during manufacture. That’s a very accurate way of locating a lens in a scope designed for automated assembly. The problem is that it’s usually on the wrong side of the lens element to handle the shock of a piston slamming into the end of a compression chamber. The soft aluminum tubing using to make inexpesive scopes will deform as the lens cell is repeatedly pushed against it by recoil.
This style of construction is not found only in inexpensive scopes; many scopes costing $200 and up are built this way as well, and while such scopes would work fine on even magnum caliber rifles, a spring airgun can shake them loose in only a few hundred- or sometimes a few dozen- shots.

So the first thing to look for in inexpensive and moderately priced scopes is a guarentee that they’ll work in airguns- Bushnell, Simmons, and BSA (and others) sell many moderately priced scopes that come with a guarentee. Some of the very inexpensive scopes at places like Cheaper Than Dirt also come with a guarantee. The better scopes made by Burris and Leupold don’t use the rolled-ring method and can easily stand up to spring gun recoil. And of course, pneumatic guns don’t have this problem and can use any scope that will fit- so long as it’s parallax corrected for airgun ranges.

That’s another term you’ve probably come accross- “parallax corrected”. What does it mean? Close your left eye and old your hand at arm’s length so that your thumb covers some object. Now close your right eye and open your left eye. Your thumb is no longer covering the object. That’s parallax error.

In any telescopic sight, there are three basic functional units: The objective lens, which forms an image of the target; the reticle, or crosshair, which provides the aiming reference; and the ocular lens- the one you look through- which magnifies the reticle and the target image.

In a properly adjusted scope, the objective lens is focused so that the image is formed in the same plane as the resticle, and the ocular lens is adjusted so that both the reticle and the target image are in focus. Typically the ocular lens is adjustible so that individuals can fine tune it to their eyesight. The objective lens is typically not adjustible, except in high-power scopes; this is because the eye can adjust and adapt over a fairly wide range. The scope might be adjusted for, say 20 yards, but the eye can compensate enough to focus at from 10 to 50 yards.

But even though the eye might be able to compensate at 50 yards, the actual focused image will not be in the same plane as the reticle. Try this looking through a high-powered scope: Move your head slightly from side to side, and see if the position of the reticle moves relative to the target. If it does, you have parallax error. That error is enough to put you off by several inches, and that’s one of the reasons field target shooters almost all use scopes with adjustible objective focus. Low-powered scopes don’t show as much error. I have a 6x Burris Mini on a Theoben Sirocco that seesm to show alomost zero error from 10 to 55 yards. My 6-18x Simmons, though, when set for 18x, isn’t nearly as tolerant. And the 30x scopes I’ve seen used by some Field Target shooters need careful adjustment, both to minimize parallax, and just to get within the eye’s focusing tolerance.

If you do have a scope with a focusing objective, checking for parallax is a good way to make sure your focus is perfect. Although your eyes will compensate for a slightly out of focus scope, this can cause eyestrain, which isn’t ideal when you’re trying to put a pellet in a 1/4″ target at 50 yards.