British aircraft machine guns of WWII
* The Lewis gun's rate of fire would "accelerate" the longer the trigger was pressed. The Lewis gun was prone to more stoppages than the Vickers K gun, and those stoppages were harder to clear. This made the Vickers K much more popular with air gunners. The Vickers K was in widespread use by the RAF early in the war and it would have been rare for a Lewis to have been used in combat by the RAF. Meanwhile the Fleet Air Arm still retained the Lewis gun early in the war, but Vickers K guns were "obtained" whenever possible.
Non- aircraft machine guns for comparison
** Depending on model. Early model model Besa guns could be switched between high or low rates of fire. The higher rate of file mode was deleted from later models.