Faster Isn't Always Better
Why Muzzle Energy Is An Important Factor In Air Rifle Hunting
By Scott Thomas- co founder of Airgun Depot
The airgun industry is notorious for touting the FPS (feet per second) of their airguns. When we first started Airgun Depot back in 2002 1000 FPS was the standard for spring powered air rifles. Now we are seeing manufacturers tout speeds up to 1600 FPS. It seems like every year we see the FPS of air rifles on the rise. The manufacturers are "keeping up with the Jones'" so to speak, each one trying to out do the other. Hey, even we get caught up with the high FPS numbers and use them in our advertising for certain air rifle models. While there is no doubt that air rifles are getting more powerful as new technologies come on board, FPS isn't all that it's cracked up to be.
First off, manufacturers use very light alloy pellets when they chrony their air rifle models. Also,some manufacturers will use the age old trick of dieseling to reach their FPS claims. If you don't know already, dieseling occurs when you put a tiny drop of a flammable substance such as diesel fuel in the hollow part of the pellet skirt. When the supercharged hot gas released by the airgun comes in contact with the pellet a tiny explosion occurs giving the pellet some extra juice. You can forget about accuracy when doing this and your airgun will probably die a fast death if you did this with every shot so we don't recommend it.
So lets take a look at why FPS should not solely be used to judge the quality / effectiveness of an air rifle. As mentioned above high FPS numbers in spring powered air rifles can only be attained by using light alloy pellets, the dieseling effect, or a combination of both. You may notice that when you fire a break barrel air rifle rated at 1200 FPS or above with light alloy pellets you will hear a loud crack. This crack is the pellet breaking the sound barrier. The speed of sound is around 1100 FPS (it varies with altitude and temperature). When a light alloy pellet is fired through a magnum air rile it breaks the sound barrel as soon as it leaves the barrel. This means that the shock wave that is created will be behind the pellet. However, the pellet doesn't stay supersonic for long and when it goes sub sonic that shock wave catches up to the pellet and can cause the pellet to tumble. This greatly affects accuracy and therefore will affect your groupings. Continue reading
A Few Air Rifles