December 16th, 2017

Tech Tip: Don’t Store Brass and Ammo Near Ammonia Solvents

Ammonia Solvent Brass Cracking MTM

Chances are that many of you have packed away your ammo and shooting supplies for the winter. Maybe you put your brass in a storage bin that might also contain solvents, old rags, or used bore swabs. Well, if you use any ammonia-based solvents, we suggest you separate the brass and ammo and keep it away from potential ammonia vapors. This is because long-term exposure to ammonia fumes can cause cracks to form in your brass. This can lead to case ruptures and possible injury.

This case-cracking phenomenon has been called Season Cracking, a form of stress-corrosion cracking of brass cartridge cases. Season cracking is characterized by deep brittle cracks which penetrate into affected components. If the cracks reach a critical size, the component can suddenly fracture, sometimes with disastrous results. If the concentration of ammonia is very high, then corrosion is much more severe, and damage over all exposed surfaces occurs. The brass cracking is caused by a reaction between ammonia and copper that forms the cuprammonium ion, Cu(NH3)4, a chemical complex which is water-soluble. The problem of cracking can also occur in copper and copper alloys such as bronze.

Season Cracking was originally observed by the British forces in India a century ago. During the monsoon season, military activity was 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. In 1921, in the Journal of the Institute of Metals, the phenomenon was explained by Moor, Beckinsale, and Mallinson. Apparently ammonia from horse urine, combined with the residual stress in the cold-drawn metal of the cartridges, was responsible for the cracking.

Ammonia Solvent Brass Cracking MTM
Don’t store ammunition (or brass) for long periods in a box or container holding ammoniated solvents:

The Australia Department of Defense (AUSDOD) has also explored the problem of brass cracking caused, at least in part, by exposure to ammonia. A study was done to see whether the amount of cracking (from ammonia exposure) varied according to the duration and temperature of the annealing process used on the brass. CLICK HERE to read AUSDOD Research Report.

Story idea from Boyd Allen. We welcome reader submissions.

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