Obturating ring

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An obturating ring is a ring of relatively soft material designed to obturate under pressure to form a seal. Obturating rings are often found in artillery and other ballistics applications, and similar devices are also used in other applications such as plumbing, like the olive in a compression fitting. The term "O-ring" is sometimes used to describe this kind of pressure seal.

Ballistics uses[edit]

Welin screw breech with mushroom-shaped de Bange obturator, and obturating ring behind

Obturating rings are common in artillery, where the hard steel casing of the shell is too hard to practically deform to provide a tight seal for the propellant gases. An obturating ring or driving band made of a softer material is the typical solution. Mortar bombs also use obturating rings to provide a seal around the projectile. Recoilless rifles and some artillery use rings with a reverse impression of the rifling cut in them for a tighter seal even at very low pressures.

Some artillery shells use an obturating ring at the rear of the shell to provide a tight seal for the breech. This allows a mostly caseless ammunition without the sealing issues generally encountered in such ammunition. The obturating ring provides the sealing that would normally be provided by a cartridge case.