Pneumatic Pnews

Sunday, January 22, 2006

What about those solid pellets?

by Tex Force

I read a lot on the airgun forums about shooting solid pellets these days. Apparently, shooters have figured out that the heavier a pellet is, the more power it generates in pneumatic guns. What they haven't yet discovered is that almost no airguns work well with them. That's what I want to discuss today.

Pneumatics favor heavy pellets
If you weren't aware of this - it's true. The heavier the pellet, the more muzzle energy it will generate in a multi-pump or precharged pneumatic. Spring guns like lighter pellets for power, but today we're looking at heavy pellets. Let me present this example. In the AirForce Talon SS (second rifle down), the Crosman Premier pellet goes about 840 f.p.s., or so. The .22-caliber Crosman Premier weighs 14.3 grains, so that delivers a muzzle energy of 22.41 foot-pounds. The same rifle averages about 735 f.p.s. with a 21-grain Beeman Kodiak (last pellet on page), and that is 25.2 foot-pounds. This same relationship holds for all pneumatics. So if you want a little more oomph, shoot the Kodiak - it's that simple. Ah, but there is a catch!

Super-heavy pellets!
If you want EVEN MORE power, what about using a heavier pellet? Well, now the shooter begins to search for the heaviest pellets he can find, and that will lead him straight to the solid lead pellets. He makes this search with the blind faith that nothing else will change - he'll just get more power from his airgun. But that's not the way things turn out. As it happens, the pellets he's been shooting are all of a similar type called diabolos. They have a narrow waist and a hollow tail. The shooter doesn't give this much thought, but that shape is quite important to the functioning of his airgun. You see, the narrow waist and hollow tail create what is known as drag on the pellet as it flies through the air. This drag is what keeps the nose pointed forward and the pellet on track. If there were no drag, the pellet would have to be stabilized entirely by its spin, which is imparted by the rifling. And that's the catch!

Airgun rifling doesn't twist fast enough for bullets
Maybe you noticed that a heavier pellet goes slower in the Talon SS. Well, if you shoot an even heavier pellet, it goes even slower. As a result, the twist rate of the rifling spins the pellet more slowly when it exits the muzzle. That doesn't matter much when the pellet is stabilized by the drag on its tail, but when the tail is filled and the side of the pellet becomes straight, as it is on a solid pellet, it doesn't have the high drag anymore. Instead of a diabolo pellet, the shape we now have is called a bullet. A bullet has to be stabilized by spin, and pellet rifles have twist rates too slow to stabilize bullets unless they can accelerate them to very high velocity. The standard twist rate in an air rifle barrel is one turn in 16 inches - too slow to stabilize a 30-grain lead bullet at anything less than about 1,000 f.p.s. The AirForce Condor (third rifle down) can get 30-grain bullets up to that speed, and so can a few Korean air rifles like the Career 707, but most pneumatics and no spring guns can!

The downrange effect
The result is that a Talon SS can shoot a one-inch group at 50 yards (under ideal conditions) with both Crosman Premiers and Beeman Kodiaks but can't keep five 30-grain bullets inside a two-foot circle! That's pretty dramatic, and it's all because the shooter did not understand how his pellets really work.

It's your choice - make it a good one!
The pellets you feed your air rifle are a personal choice, but you have to understand what they do as far as accuracy is concerned. Standard diabolo pellets are far safer than solid bullets because they travel only a fraction as far when accelerated to high velocity. The high drag on their tail slows them down like a badminton birdie. But it also gives you most of your accuracy, and it's the reason your pellet rifle works as well as it does. If you want to experiment with bullet-like ammunition, know what the tradeoffs are before you invest in too many tins.

1 Comments:

  • i do agree with what u said partially about the raising of the weight of the pellet to get more power, but u stated something like 22ft/lbs of energy which is already not much energy for a 21 gr. when u speak of 30 grain solid pellets like the eun Jin,daystate magnum and H&N rabbit magnums u have to speak of energy levels starting from 50ft/lbs onwards to have good accuracy. other wise dont look at those pellets. a 30grain solid, running 80ft/lbs is very accurate and hard hitting.

    By Anonymous subsonic, at 2:24 PM, March 23, 2006  

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