| 1. Insert an airgun pellet into the
muzzle and push it in with a pencil to a depth of 4mm.
2. Chuck the brass screw in the drillmotor
or press chuck, setting the rpm a the slowest speed if possible.
3. "Charge" (gob some on) the screwhead
with lapping compound.
4. Very lightly engage the screwhead
against the crown area of the muzzle and start the motor.
5. Using a rocking, rotating motion,
lap the crown until a slight ball-shaped depression is lapped
into the crown. Rotate the barrel 90 degrees every few seconds
during the lapping process, all the while "rockin" the screw
head or barrel to maintain the round shape of the screwhead
and distribute the lapping action across the entire screwhead
surface.
6. Check your progress every 50-60
seconds by wiping the crown clean and examining the edges
of the rifling lands where the meet the lapped crown surface.
When there is a perfectly even, sharp margin on every land
and groove as it meets the crowned surface you are done.
If it becomes obvious the original crown is so deep and
ragged the lapping is not effective the barrel must be carefully
filed or machined back to eliminate all or most of the original
crown before lapping (only expert metalworkers should perform
this phase).
7. Push the pellet out of the bore
from the breech end and clean the barrel (from the breech
of course).
8. Testfire ... it is not uncommon
for the Zero to shift, this is nearly always a sign the
original crown was bad, and accuracy will improve.
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