Artillery works best when there is a full crew of men to operate the gun.
Small guns like this take four men at least.
With Jeeps as their prime movers it is impractical to carry more then four men in the vehicle.
The Jeep only carries a small amount of ammo.
So while the guns can go into action quickly, they can't fire many rounds before they run out of ammo.
More Jeeps are needed or large trucks to carry ammo in an extended conflict.
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