In trials of the Owen, the operator went to the end of a mud-bog,thrust the gun deeply into the mud and held it there.Then he pulled it out,turned it over and submerged it again, ensuring that mud was pushed into all surfaces.
The gun was then retrieved and, without cleaning or adjustment ,proceeded to fire perfectly. THe now empty magazine was then replaced and the weapon continued firing. "Almost unbelievable ,isn't it ?" said the newreel commentator.
Because it was an Australian weapon,of course, few outsders have every heard of it.
The Owen Machine-Carbine continued in use by the Australian army in Korea and the early years of the Vietnam conflict.
(vide Arms of Destruction: Ranking the World's Best Land Weapons of WW2. Robert A Slayton, among other sources)