How erosive is cordite?

[Steve762]

Just how erosive is cordite loaded .303 vs "Z" loaded .303? Thx, Steve

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[Mk VII]

Regulations For Army Ordnance Services comments:

" 1. The action of Cordite propellant in the barrel of a .303-in. weapon is quite different from that of N.C. propellant.
Cordite gives a rapid build-up of pressure with great heat, leading to pitting and erosion of the chamber end of the barrel.
N.C., however, gives a more gradual build-up of pressure with less heat, and this in turn gives uniformity of barrel wear from chamber to muzzle, the amount of pitting and erosion being greatly reduced.

2. With Cordite propellant, set-up of the bullet is most pronounced and even when the chamber end of the barrel is well worn, the muzzle end still has sufficient rifling left to impart the necessary spin. As the wear advances up the barrel, so the accuracy of the weapon is progressively reduced.
With an N.C. propellant, set-up of the bullet is slow and by no means so pronounced, due to the more gradual building up of pressure. The barrel retains its original accuracy until wear reaches a critical stage, when a sudden falling off in accuracy occurs. "


This necessitates an arbitrary fixed barrel life on automatic weapons.