Two for Flinching

The shooting habit that’s probably the the most  destructive to shooting accuracy is flinching- that is, unconsciously reacting before the shot is fired. This is most common with loud and high-recoiling firearms, but it’s pretty common with airguns as well, especially with shooters who who don’t have firearms experience. Luckily it’s pretty easy to cure.

If you find that your shots always string out to the right (for right handed shooters), or that you close your eyes when you pull the trigger, or that you repeatedly jerk the trigger instead of squeezing, you may be flinching. In the case of firearms, the general advice is to alternate heavy and light loads, or load a revolver with a mix of loaded and empty cylinders. With an airgun, of course, you can’t do that. But the low velocity of airguns (relative to firearms) you can do something that’s impossible with firearms: You can watch the pellet.

To do this, pick a heavy pellet- the 10.5grain Crosman Premiers, or Beeman Crow Magnums or Ramjets come to mind- and shoot outdoors at 20-30 yards, using the gun’s iron sights. Side lighting helps.

Concentrate on watching the pellet from the moment you can pick it up leaving the barrel until it hits the target. At first, you won’t see it at all. Then you’ll catch a glimpse, and eventually you be able to see it for a major portion of its trajectory. And by the time you can do that, your flinch will be cured.

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.

1000fps!

When I started shooting airguns, 1000fps was an unheard of velocity in airguns. Today, every maker seems to offer a variety of guns advertised as 1000fps guns, and one maker brags that his rifle produces 1200 fps. Has technology improved that much?

No. What’s happened is that makers are testing guns with very light pellets, and in some cases putting in springs that are far too strong for the gun’s design. resulting in poor accuracy and early failure- all in pursuit of the fabulous 1000fps barrier. But these number are very misleading- and making a pellet go 1000fps or faster is not really very desirable. Here’s why.

Velocity alone tells you nothing; a felt cleaning pellet will easily exceed 1000fps in most rifles, but it won’t go very far, and it won’t do much damage compared with a lead pellet. What really characterizes the amount of power available in an airgun is the muzzle energy, measured in foot-pounds. To compute muzzle energy, you need to know the weight of a pellet, in grains, and the velocity of the pellet. This can be measured with an inexpensive chronograph like the CHRONY- an invaluable tool for any serious airgunner, by the way.

shooting chrony

(These start at $89.95- I’ve owned mine for at least ten years. You can find them at most airgun suppliers, or buy them direct from the company.) Once you know the velocy and the weight of a pellet, the formula for energy is:

E = m·v2/450437

Let’s consider a gun with an advertised 1000fps muzzle velocity when tested with light 6.5 grain pellets like the Beeman Hobby pellet:

6.5 * 1000 * 1000 / 450437 = 14.43 ft-lbs.

That’s not bad, but consider that my Theoben acheives 980fps with 7.9gr pellets- that’s almost 17 foot pounds- with a slower pellet.You can see right off that velocity doesn’t really tell you what an air rifle is capable of- muzzle energy is a much better measure. And that slower, heavier pellet has a number of advantages beyond having more energy to begin with.

As a pellet approaches the speed of sound- 1000fps- drag shoots up exponentially. A lot more energy pushes the pellet only a little faster. It’s very inefficient.

Second, as the pellet rapidly deccelerates from supersonic to subsonic speed, it goes through the transonic region- a region of great aerodynamic instability. It’s better in general to start out subsonic and stay there, or, if you have enough energy available, start supersonic and stay there thoughout the flight.

Airguns don’t have all that much energy, though; a .22 Long Rifle cartridge has over 90 foot-pounds of energy available- quite a bit more than all but the most powerful large-caliber airguns. Yet target .22 cartidges are designed to propel the bullet at subsonic velocities.

Generally, then, when selecting pellets for an airgun, it’s a good idea to start with pellets that stay subsonic. Target guns with 5-7 ft-lbs of muzzle energy work well with light (6-7gr) target wadcutters. Guns over 12 ft-lbs should use heavier pellets, And guns producing close to 20 ft-lbs in .177 should use the very heavy pellets, like Crosman Premier 10.5gr pellets and Beeman Crow Magnums.

Another advantage of heavier pellets is that they have a higher sectional density for a given caliber. That means that the ratio of mass to diameter is higher- and that means proportionally less drag for a given level of energy. Another advantage is more resistence to wind- and you can start to see why some field target shooters choose heavier pellets even though they’re less efficient than some lighter pellets in a given gun.

Scopes for Airguns, part IV: Sighting In

Sighting in an airgun scope is pretty much the same whether you’re sighting in a 4x fixed power scope on a plinker, or an 8x24x on a Field Target gun. The first task is to decide at what range you’re going to sight the gun in at. And to decide that, it helps to visualize the path of the pellet after it leave the barrel of the gun.

If the scope and the gun barrel were perfectly parallel, a pellet would begin its flight an inch or two below the scope, and then continue to drop lower and lower, as gravity pulled it towards earth; the pellet would never hit what the scope was pointed at.

If, however, the barrel is pitched up slightly, the pellet will rise untiil it meets the line of sight, and then begin its descent. The pellet will hit where the scope is aimed at one distance. At other distances it will hit low to some degree.

But if the angle is increased a bit more, the pellet will ride above the line of sight of the scope, and then slowly descend, thus crossing the line of sight twice. If you choose two distances within, say, 40-50 yards, a distance, not only will the pellet will hit exactly where the scope is pointed at two distances, it will be close in between these two distances as well.
For typical pellet velocities of 700-900fps, sighting in so that the first crossing occurs at about 20-22 yards is a good starting point. The second crossing will be at around 40 yards, and a hunter knowing the trajectory will be able to make clean hits over a wide range with very little error.

Having made that decision, how best to actually sight in the scope? Start by placing a large paper target at 20 yards, preferably one with both concentric rings and a large cross. Align the scope visually so it’s parallel with the barrel. Now shoot a group of 5 shots, aiming at the dead center of the target. You should get a reaosnably tight group of pellets somewhere on the paper. If none of the pellets hit the paper, bring the target closer- say 5 yeards- and try again. You might also want to adjust the scope mount, if it’s adjustible, before you start adjusting the scope.
If you have a gun vise, the next part is easy; if not, it’s a bit tougher, but not impossible. Hold or clamping the gun so that the scope points at the center of the target. Now adjust the windage and elevation knobs on the scope so that it points at the center of the group of pellets you fired. Shoot another group- this one should be dead center, or close to it. Continue shooting and adjusting until the pellets group right around the center of your point of aim.
If your groups move to the right or left when you adjust elevation alone, your scope is tilted with respect to the gun, or you’re holding the gun  at an angle when you shoot. A scope level- which you can make- is a good way to check on this.

Now shoot groups at 30, 40 and 50 yards, adjusting windage to keep the groups centered, and making a note of how much the pellets rise or fall at each range. From this, you can put together a table of corrections that will tell you about how much to hold over or under when shooting at various ranges.

Sighting for Field Target is a bit more complex, but we’ll tackle that another day.