Supplementary data for: Surface damage of perpendicular and oblique bullet impacts in stone

Controlled experiments were conducted to investigate the surface damage
caused by perpendicular and oblique impacts of bullets into sandstone and
limestone targets. Individual bullets fired in conditions simulating
modern rifles at typical combat distances excavated craters with diameters
from 22 to 74 mm and depths from 4 to 24 mm. Limestone target craters were
up to twice as large and deep as those in sandstone. These craters have a
complex shape consisting of a central excavation surrounded by a shallow
dish, compared to the simple bowl shape of most sandstone impacts. Radial
fractures extending to the edge of the target block were common in
limestone targets. Impacts at an angle of 45° to the surface in both rock
types result in asymmetric craters. Two common types of ammunition were
compared: the steel-tipped NATO projectile generally produced larger and
deeper craters than the projectile that is commonly fired from AK-47
rifles, despite having approximately half the mass of the latter. These
results characterise the sort of damage that can be expected at many sites
of cultural significance involved in contemporary conflict zones, and have
important implications for their conservation.