Scavenge arty is, as we say in the business, 'bugged to fuck'.
As far as i can tell after making good use of the commander, every time you hit a milestone in munitions that WOULD mean it does an additional round of shells, it re-calls the entire ability where you last dropped it.
Usually around multiples of 100, I find. Would be worth checking with a stats guy to see what the actual values are for this offmap to increase in shell number so I can compare in game.
It's not bugged any more AFAIK
I have used this ability quite a few times on bases with 300+ munitions and it's never completely destroyed it in one go (two probably would)
I think the main issue is just that it covers such a huge radius (the circle fits almost perfectly around the US base
). So the solution would be to reduce the radius and reduce the time it takes for the shells to land, to compensate, because it takes too damn long and I've never hit anything with it other than base buildings