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November 27, 2007

Inaccurate Airguns - Diagnosing the Problem

One of the most frustrating things a person can do is to buy a product only to find it doesn't live up to your expectations. In the airgun world, this means buying an airgun, then finding out it doesn't shoot quite as accurately as you think it ought to. Figuring out why the airgun doesn't shoot accurately can be a frustrating experience. Let's take a look at some of the causes of an inaccurate airgun.

First of all, if you are using a spring-piston airgun, the most common cause of innaccuracy that I have found is loose stock screws, the screws that hold the action of the rifle in the stock. When these are loose, the gun shifts each time you fire it. Maintaining a snug fit is important for the gun to reliably shoot at the same point of aim each time. If your stock screws are loose, tighten them. If they won't stay tight, remove them, clean them off with a degreaser, and re-install them with some Loctite to ensure a snug fit.

In the world of springers, you will often find that scope creep, the moving of the scope upon firing, becomes an issue. Using proper mounts and a scope stop will solve this problem for you. Again, a little dab of Loctite on the scope stop and mounts will assist in keeping the scope from moving. I've actually had a scope pop off the gun while trying to stop a fleeing fox squirrel. It's quite agravating!

Continuing on with spring-piston type airguns, don't forget to clean the barrel before using it the first time. There are preservatives and occasionally packing junk in the barrel, and none of that stuff is there to help you with accuracy! So move it! Use some cleaning swabs (don't use firearm solvents) and wipe the barrel clean.

Oiling the spring piston airgun is almost always overdone. You don't want excess oil in the chamber since it will cause dieseling, the combustion of the oil during the firing process. Your velocity will fluctuate wildly from shot to shot, and accuracy will suffer greatly.

Be sure the lockup of the gun is firm. A break-barrel rifle will sometimes get a loose barrel pivot, and the gun will not return to the same point of alignment after each cocking action. Movement during the firing cycle will throw off your accuracy every time!

How you hold your springer can affect accuracy. Hold it lightly. It isn't a centerfire that requires you to tuck it into your shoulder as if it will throw you to the ground when you fire. It's an airgun! Lighten up, and your accuracy will improve. 

The following accuracy issues are common to all airguns, not just spring piston type airguns:

A bad crown on the muzzle will invariably affect your accuracy. Inspect the crown of a suspected inaccurate rifle to see if the muzzle is uniform. You may need a magnifying glass for this, or you may not. Recrown the barrel if needed.

Pellets - every airgun has a favorite food, just as most people have a favorite food. Find what your airgun likes and use that for the best results in accuracy. Cheap pellets aren't often uniform enough to produce shot-to-shot consistency. Use a pellet that is well-made and uniform in size, shape, and weight.

Trigger use - squeezing the trigger lightly while concentrating on the sights will work better than yanking or pulling the trigger. The shot should almost be a surprise if you are using a consistent squeeze on the trigger. Often new guns have a "rough" trigger and need some wear-in time to smooth out the action. Shoot a tin or two of pellets through the gun before you worry too much about this problem. Give the internal parts a chance to smooth out and get used to each other.

Your follow-through upon firing is important. Airguns take longer for the projectile to exit the barrel than firearms. Hold your sight picture after the shot, and try not to move as soon as the firing action starts. Give the pellet time to exit the barrel and get away from outside influences before you move from your stance. 

So if your airgun isn't as accurate as you'd like, take a look at some of the causes we just went over and see if one of them isn't the culprit to your inaccurate airgun. 


November 07, 2007

Sight Height of Scope above the Barrel

In an earlier blog entry, I gave you a link to a calculator that helps you determine the Optimum Point Blank Zero for your particular scope, gun, and pellet combination. This calculation is provided by Steve in NC as he is known on the YellowForum, an airgun enthusiast site. However, it occurred to me that some of you might not be able to determine the scope height on your gun. Here is a simple way to get that particular number without a great deal of trouble and calculation on your part.

Take a sheet of aluminum foil and cover the objective bell of your scope, creasing around the bell edge to make the circle appear on the foil. Now remove the sheet and poke a small hole in the center. Replace the foil on the scope again and take the next step.

Place a cardboard or other suitable target material one foot in front of your muzzle....that's right, just one foot. Draw a point of aim such as a small dot on the target. Find the point of aim in your foil-covered scope and fire a shot. Measure the distance from the point of aim to the hole made by the pellet, and you have a very close measurement of the scope's height above the bore.

You will need to illuminate the point of aim with a good light since the foil defeats the incoming light to the scope. If you need a visual to help understand the above process, here is a link that will assist you in this little experiment.


I'd love to hear back from those of you who decide to try this little experiment, as well as how well the calculations work for you in determining the Optimum Point Blank Zero. The more accurate your airgun becomes, the more fun it is! 

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