Walls or doors of construction resistant to penetration of a bullet of 150-grain M₂ Ball ammunition having a normal velocity of 2,700 ft/sec fired from a 0.30-caliber rifle distance of 100ft perpendicular to the wall or door.

When a magazine ceiling or roof is required to be bullet-resistant, the ceiling or roof shall be constructed of materials comparable to the sidewalls or other materials that will withstand penetration of the bullet described above when fired at an angle of 45 degrees from the perpendicular.

Tests to determine bullet resistance should be conducted on test panels or empty magazines that will resist penetration of 5 out of 5 shots placed independently of each other in an area at least 3.ft x 3.ft.