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26 October, 2013

Detailed Performance Information for the QB79 PCP Repeater

Here's some more detailed information on performance of the QB79 PCP Repeater. In particular, this post is to show the outstanding consistency of muzzle velocity that's available with this product.

Our test results for the .177 cal QB79 PCP Repeater were recorded, fed into a spreadsheet and plotted out as a graph.

As you can see, the different tune levels were achieved in three ways.

The greatest consistency - with 168 "good" shots, but lower (760 fps) muzzle velocity is achieved using the standard factory hammer spring. This gives the most efficient performance in terms of total muzzle energy (1,669 ft/lbs - the sum of the muzzle energies for each individual shot) before reaching the 30 fps Extreme Spread shot, but the lower muzzle velocity is not what many people would prefer.

More muzzle velocity (800 fps), but less (120) good shots, is obtained by slightly shimming the hammer spring with a couple of washers. This gives less efficiency, with a total of 1,336 ft/lbs of muzzle energy before the 30 fps Extreme Spread shot.

The third level of tune combines the shimmed hammer with the Archer Airguns XP Tuned Valve. This is a real air hog, with much lower efficiency (just 842 ft/lbs total muzzle energy before the 30 fps ES), but it does deliver the highest muzzle velocity of 840 fps with 68 "good" shots - still enough to complete many field target courses without refilling with air.

Here's the test targets for the mid level (800 fps and 120 good shots testing). Each target has 5 bulls, shot in the sequence shown and with the Chrony prints stapled next to each target.

Here's the same data presented for the QB79 Repeater in .22 caliber.

The gun is more efficient in .22 caliber, with total muzzle energy of 1,844 ft/lbs for the 575 fps/180 good shots level. At 125 good shots, it's 1,700 ft/lbs total and 839 total ft/lbs for the maximum muzzle velocity (690 fps) tune level.

Please note that in all cases, these tests were made with unsorted Crosman Premier Hollow Point pellets, fired "straight from the tin" at 10yards range.

I hope this gives some useful and interesting detail to those who have questions about the performance of the QB79 PCP Repeater.


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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