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28 July, 2010

Now we can really understand temperature effects on our QB78 family air rifles!

I've always been interested in the effect of temperature on CO2-powered air rifles such as the Crosman 160, QB78 and Crosman 2260.

As all CO2 air rifles exhibit a change in muzzle velocity with changes in temperature - due to the physical properties of CO2 - I've tried to measure this effect in the past. In tests, I found that QB78 family air rifles - such as the QB79 and AR2078 - all show an increase in muzzle velocity with temperature of 2 fps per degree F. So, a gun shooting at 600fps at 65 degrees F will shoot at 640pfs at 85 degrees F, due to the effect of temperature alone. And I measured the point of "valve lock" on a QB78 air rifle to be at 96 degrees F.

But, like everyone else, I've concentrated on the air temperature to measure these things. Now, there's a completely new way to measure the temperature of your QB78 family air rifle. It's the Archer Airguns QB78 Temperature Monitoring Kit.

Thanks to the suggestion of Rochester-area airgunner Doug Wall, Archer Airguns has introduced a simple kit that allows you to monitor the temperature of the CO2 in the gas tube of your air rifle. This kit uses self-adhesive thermometers that attach to the main tube of the gun and, therefore, measure the temperature of the gas tube rather than the surrounding air.

These thermometers allow measurement of main tube (and therefore CO2) temperature to 1 degree F. If the temperature is highlighted in green, it's exactly the value indicated. Brown highlight shows that the temperature is just above the temperature, while bluehighlight shows a figure just below. In this way, you can see differences in muzzle velocity of 2 fps!

Here, the thermometer shows a main tube temperature of 73 degrees F.
You can use this kit to maximize the muzzle velocity of your QB78 air rifle. In testing, I found that simply piercing a fresh pair of 12 gram Powerlets in a QB78 reduced the main tube temperature by 10 degrees F. That's a loss of 20fps!

And, using the Temperature Monitoring Kit, I saw that it took 5 minutes for the temperature of the main tube (and, therefore, the CO2) to return to 65 degrees, re-gaining 10 fps in muzzle velocity in the process.

As the Archer Airguns QB78 Temperature Monitoring Kit is new, there's lots of information on the performance of our favorite air rifles that can now be explored in a way that was previously unattainable. Watch out for more data, or use the kit yourself and contribute to our increased understanding of how these air rifles really behave!


Anonymous,  Friday, 30 July, 2010  

Hi, found an old 160 at the local used funiture store. Trying your pellgun oil treatment. Lots to learn. Thanks for all the info...


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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