Accurizing the QB78 air rifle
by Frank (airbuddy3)
Why do I want to accurize my QB it already does one holers? Well it will do the same
one holers farther out and with more types of pellets. And, franky - just to see how good
this Chinese rifle can really get !
Start by deburring the port inside the barrel. Whether modded or not, the factory leaves
it sharp and any porting does the same. This sharp edge damages the pellets and its
amazing that it can shoot accurately with the sliced pellets.
Use valve grinding compound on a cotton brush and move it back and forth till it catches
less, apply 2-3 times. After the polishing with the valve grinding compound, clean the
barrel and the brush using Goo Gone until both are very clean.
Next, apply some fine polishing compound (such as the white colored type that is
used in auto body work) to the cotton brush and proceed to polish the entire length of the
barrel. After about 20-25 strokes the cotton brush becomes dark. Clean the barrel and
brush with Goo Gone, then reapply the polishing compound - repeat 4 -5 times. Give a final
Goo Gone cleaning when finished.
Recrown the barrel with a round head brass wood screw that is chucked an electric drill.
Place a pellet into the front end of the barrel, apply some valve grinding compound, and
slowly with the screw centered over the bore apply light pressure and slow speed.
Inspect your progress with a magnifying glass and repeat the process until you see that a
new crown has formed - even and somewhat shiny. Then clean off the valve grinding compound
and using some polishing compound - slowly and carefully apply at low speed. Repeat a
couple of times until crown is nice and shiny. Clean the barrel a final time with Goo Gone
and reassemble to gun.
Touch up the new crown with cold blue and inspect your work with a magnifying glass. It
should show the ends of the flats and lands and should be even and centered.
Target test the gun using various pellets. It is better to lube the pellets using Krytech
or a similar wax product - this enhances accuracy and helps prevent lead fouling. More
importantly, lubing can prevent corrosion (remember CO2 will cool the barrel and there
will be a tendency for condensation to occur). Repeated use of the wax will
continually polish the bore .
