Nellis artillery timing details
The key to avoiding the artillery is to move from building-to-building up the northwest side of town toward the front gate. Stick to the high cover in the northeast corner of the two buildings, then make a bee line for the gate. The Boomers won't shoot at their own people, so stick to the fence until you make it to the gate. Also, I know there is an old train tunnel that enters the area from the south, but no one has ever come back out of there to say it is safe.