WHEN TO CLEAN THE M40A1 ~
BEFORE FIRING: The rifle MUST ALWAYS be cleaned prior to departing on a mission, or firing the weapon on a range. If not cleaned prior to firing, t he extra solvent or lubrication remaining in the bore will cause a puff of smoke or steam, and possibly allow detection by the enemy. Also, the extra fluids cause an increase in chamber pressure that cause an increase in elevation of the first round fired.
AFTER FIRING: The rifle must be cleaned after it is fired because firing produces deposits of: (1) primer fouling, (2) powder residue, (3) carbon, and (4) metal filings. These deposits collect moisture and cause rust. Although modern ammunition has a noncorrosive primer which makes cleaning easier, the primer still leaves a deposit.
The rifle must be cleaned within a reasonable time interval (a couple of hours) after completion of firing. Repeated firing will not injure the rifle if it is properly cleaned prior to the first round. After a weapon has been fired, it must be cleaned for, at least, three consecutive days. For several days after firing, check the rifle for signs of corrosion and fouling by running a clean patch through the bore.
Graphite and carbon deposits will sweat from the pores of the metal for three days. Thus, the need for repeated cleaning.