Well basically,
This happened to me and 3 other mates. So four of us...
We had one wonderwaffle but he went down, we revived him. Somebody else got the wonderwaffle in the box. His ran out of ammo and me and the fourth guy got them at the same time.
Also, even though we all had it, it was still in the box. We found that if you swap the wonderwaffle for a wonderwaffle in the box you get full ammo in the new wonderwaffle. You cant have 2 wonderwaffles tho and if you try and take it you will lose a gun.
Its good fun when you all have one, so hard to die