Welin breech block

The Welin breech block was a revolutionary stepped, interrupted thread design for locking artillery breeches, invented by Axel Welin in 1889 or 1890. Shortly after, Vickers acquired the British patents. Welin breech blocks provide obturation for artillery pieces which use separate loading bagged charges and projectiles. In this system the projectile is loaded first and then followed by cloth bags of propellant.