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13 June, 2010

FPS Specs on QB78 Family Air Rifles

We received a very interesting email from a potential customer who asked "The FPS data on your site is different than that of Shanghai Air Gun Factory's, the producer of the gun, by 50 FPS... Why? Also, I'm having trouble finding any reports on your products "power"... Do you know if it's capable of taking out small pests, such as squirrels and birds?"

In answer, I replied that all CO2 air rifles - not only the QB78 family - have an "envelope" of performance depending on temperature, pellet type and aftermarket tuning. This is why the "power" of these guns is not a fixed value. In more detail...

As with all airguns, muzzle velocity will vary with pellet weight and (to some extent) shape. Heavy, flat-fronted wadcutter pellets shoot slower than lighter, pointed pellets.

And, all CO2 guns have a muzzle velocity that's dependent on temperature (higher temperature gives higher muzzle velocity at the rate of 2 fps per degree F).

I show the performance of the QB78 family air rifles as being 500fps at 65 degrees F for .22 caliber and 600 fps at 65 degrees F for .177 caliber. These are average muzzle velocity figures that will be achieved in our "Gold Service" testing with heavy wadcutter pellets - and that therefore I can prove to a customer.

Let's take a .22 caliber gun as an example. At 65 degrees F and 500fps with 13.86 grain wadcutter pellets, the muzzle energy is about 7.7 ft/lbs, which is marginal for humanely killing small pests without very accurate shooting.

Now, at 85 degrees F, the average muzzle velocity will be 540fps for .22 caliber using the same wadcutter pellets. This is due to the temperature effect already described. Now the muzzle energy is about 9 ft/lbs, a significant improvement for hunting.

If you choose to add the Archer Airguns "XP" Tune Kit, the muzzle velocity - still at 85 degrees F and with the same pellets - will be about 640fps, meaning 12.6 ft/lbs of muzzle energy. This is very suitable for hunting small critters and birds. The tune kit increases the muzzle velocity by making the flow of gas inside the gun much more free.


About This Blog

This blog shares information, ideas and knowledge about air rifles. It compliments the information Stephen publishes on the Archer Airguns website, on YouTube and the Chinese Airgun Forum.

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