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05 February, 2011

The QB78 HDD Pays For Itself in Six Tins of Pellets!

Steve_in_NC writes...

Hammer debouncers are an accessory with a number of advantages, including improved muzzle velocity consistency (due to reduced evaporative cooling and consequent better pressure stability), quieter muzzle-blast, and reduced hammer vibration. But one that's not often mentioned is this. They may be the only accessory that can pay for itself. Here's an example for the QB78 HDD. I did a little math on the economics of CO2 "gas mileage," and came up with the following intriguing result for QB78 family air rifles that have had the Archer Airguns XP Tune Kit installed.

Typically, shot count per fill of CO2 runs about 35 good shots with the XP Tune kit in place. Adding the HDD improves the number of good shots by over 40% with no impact on muzzle velocity, thus adding approximately 15 additional shots per fill.

I looked up prices for Powerlets, and found that a typical cost for Powerlets (Pyramydair boxes of 25 - not counting shipping) is $0.60 each, so that it costs 2 x $0.60 = $1.20 to recharge a QB78. At 35 good shots per fill in an undebounced XP-fitted QB78, that works out to $1.20 / 35 = $0.034 worth of gas per shot. The "free" extra 15 shots per fill provided by the HDD are therefore worth 15 x $0.034 = $0.514 per fill.

Thus, the HDD will pay for itself in saved gas in $27.99 / $0.514 = 54.5 fills.

That works out to a free HDD in 54.5 fills x 50 shots/fill = 2723 shots = less than six tins of pellets!


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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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