Week 6 and 7. These two weeks are dedicated to extensive weapons training. More so than any other service, the Marine Corps provides all-out live-fire training with the M-16 rifle. You'll fire on a variety of courses, still and moving and pop-up targets, normal ranges, combat ranges, etc. All Marines must qualify as a "marksman" before this two week period is complete (and virtually all will).
Before you actually get to fire however, you
will practice aiming and dry-firing your rifle until you simply can't
stand
it anymore. By the time you fire that first actual shot, you'll have dry-fired
your rifle in every conceivable position thousands of times.
In addition to rifle training, during these two weeks, you'll receive basic training on grenades and other types of weapons.
During week 7, you'll also experience a 6 mile night march, and get another chance at the Confidence Course.