Season cracking

During the monsoon season, military activity was temporarily reduced, and ammunition was stored in stables until the dry weather returned.

Many brass cartridges were subsequently found to be cracked, especially where the case was crimped to the bullet.

It was not until 1921 that the phenomenon was explained by Moor, Beckinsale and Mallinson: ammonia from horse urine, combined with the residual stress in the cold-drawn metal of the cartridges, was responsible for the cracking.

If the cracks reach a critical size, the component can suddenly fracture, sometimes with disastrous results.

The problem was solved by annealing the brass cases after forming so as to relieve the residual stresses.