from firing, to obtain a chemically clean surface, and in coating
this surface with a film of oil to prevent rusting. The fouling
which results from firing is of two kinds--one, the products
of combustion of the powder; the other, cupro-nickel scraped
off (under the abrading action of irregularities or grit in the
bore). Powder fouling, because of its acid reaction, is highly
corrosive; that is, it will induce rust and must be removed.
Metal fouling of itself is inactive, but may cover powder fouling
and prevent the action of cleaning agents until removed, and when
accumulated in noticeable quantities it reduces the accuracy of
the rifle.

(b) Powder fouling may be readily removed by scrubbing with hot
soda solution, but this solution has no effect on the metal fouling
of cupro-nickel. It is necessary, therefore, to remove all metal
fouling before assurance can be had that all powder fouling, has
been removed and that the bore may be safely oiled. Normally,
after firing a barrel in good condition the metal fouling is
so slight as to be hardly perceptible. It is merely a smear of
infinitesimal thickness, easily removed by solvents of cupro-nickel.
However, due to pitting, the presence of dust, other abrasives,
or to accumulation, metal fouling may occur in clearly visible
flakes or patches of much greater thickness, much more difficult
to remove.

(c) In cleaning the bore after firing it is well to proceed as
follows: Swab out the bore with soda solution (subparagraph j)
to remove powder fouling. A convenient method is to insert the
muzzle of the rifle into the can containing the soda solution
and, with the cleaning rod inserted from the breech, pump the