There was another one in Battlefield 1 - an experimental machine gun with two magazines, but only one could be engaged at a time. You would pull one out slightly and push the other one in. The idea was to be able to switch between two different types of ammo for increased versatility (e. g. regular ammo against infantry and incendiary for anti-air). As with most weapons featured in Battlefield 1, I think this was a prototype that never saw any real action.
There was another one in Battlefield 1 - an experimental machine gun with two magazines, but only one could be engaged at a time. You would pull one out slightly and push the other one in. The idea was to be able to switch between two different types of ammo for increased versatility (e. g. regular ammo against infantry and incendiary for anti-air). As with most weapons featured in Battlefield 1, I think this was a prototype that never saw any real action.