Browning M1919 Machine Gun
Browning M1919A4, better known as the '.30 Cal' machine gun. Still used and manufactured today in some countries. It was also fitted with a bipod and stock as shown. This was known as the M1919A6. Below is an image of a Swedish Ksp M42.
And there also was the ANM2 - same as the 1919 but a lighter version for aircraft use. British versions were made by Vickers Armstrong in .303 calibre for Spitfire planes.
British Commonwealth Variants and Designations
Sear hold-open conversion of previous L3A1s and L3A2s. The A3 is the modified version of the A1, and the A4 is the modified version of the A2.
C1/A1 and C5/A1
Canadian designation for 7.62x51mm rechambered M1919A4s for fixed (C1) and flexible (C1A1) applications. The C5 and C5A1 were product improvements of the previous C1 and C1A1 respectively.