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02 May, 2010

Hot-Rodding QB78 Family Air Rifles

Post by Ron Robinson:

Sweet as the Chinese QB78 family CO2 air rifles – the QB78, QB79 and AR2078 etc - are in stock form, they are equally sweet platforms for all manner of customizations. Their modest price-tags minimize the angst of defacing an expensive piece in the quest for “personalization”, while the end result of even simple modifications can be incredibly gratifying. Thankfully Archer Airguns offers many of the parts and accessories necessary to get one well on one’s way.

As in any hot-rodding, simple modifications can return satisfying performance increases. For shooters of the Chinese QB78 family CO2 rifles, the most “bang for the buck” is the Archer Airguns XP tune kit. Requiring minimal mechanical skills, the XP kit is the closest thing to simple, bolt-on horse-power. A small expenditure and simple installation will return gratifying power increases.

For more serious power-freaks, there are modifications akin to turbo-charging these Chinese CO2 rifles. Converting a QB or AR series CO2 rifle to high-pressure air, at pressures safe for the design, completely transforms the personality of an unpretentious plinker… into something of a beast! At temperatures of 90-100 degrees F., Co2 pressures exceed 1,200 PSI, at which point some Co2 guns will display symptoms of “valve-lock” by shooting less powerfully, or not at all. Employing a 3,000 PSI air bottle REGULATED TO NO MORE THAN 1,250 PSI OUTPUT on an AR-series rifle insures the gun receives pressures no higher than it would on Co2. Utilizing an appropriate burst-disc on the output side of the regulator (say 1,800 PSI) insures against catastrophe in the event of regulator failure.

While a stock .177 QB or AR moseys along at 8-10 foot pounds of muzzle energy, and modified examples may aspire to 12 foot-pounds on CO2, the same rifles operating on air can easily attain 14-15 foot-pounds. Hopped-up further, a .177 can approach 20 foot-pounds of muzzle energy, and a .22 can push 25 foot-pounds! It is entirely possible to double the power of the Chinese CO2 rifles.

In stock form, my own QB77 Deluxe maxed-out at about 9-10 foot-pounds on CO2. However, after several modifications and evolutions (into an AR bulk-tank gun), she now produces 17+ foot-pounds at a regulated 1,250 PSI (from a 3,000 PSI air bottle). Granted, such performance did not come from simple bolt-on modifications; however the tinkering, testing, and trial-and-error involved was a great learning experience that produced a rifle competitive against the finest field-target rifles in the world. Averaging just over one-half-inch groups at fifty yards, thankfully my baby lost none of her endearing qualities in the evolution from modest plinker to “spoiler” field-target rifle.

You’ve come a long way, Baby!


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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