Unironically Louis Chauchat. If memory serves the mags didn't work in testing when they tried to close them. And they needed machine guns now more than they needed good ones after they would have lost.
One is meant to just hold down the trigger until it's empty. The Chauchet was one of the first of what we would know as a light machinegun. Mobility in order to support advances was the designated role.
In a world of bolt action rifles, the ability to lay down controlled bursts was a big firepower multiplier.
The 20 round magazine would be acceptable for the period. Same capacity as what the M1918A2 BAR was issued with in WW2 and Korea, and only slightly less than the many light machineguns with 30 round magazines that were used for decades after (and in some cases into the current day.)