41 Johnson

[Jack]

If I recall correctly, Marine parachute units were equipped with Johnsons. The reason being that the Johnson's barrel can be removed easily- the rifle and barrel were put into a padded case during the parachute jump.
The Marine Raiders may have used Johnsons, too, early in the war when Garands were scarce.
The magazine was considered a possible drawback by the review boards that tested weapons. The Johnson also (so they reported) didn't cycle perfectly with a bayonet attached.