Paintballs are wash offable. I place my pellet trap on my retaining wall which is made of that concrete stackable brick and when the sprinklers in my yard go on, the paint goes away. The paintball shells however I usually pick up by hand, I don't think they break down in the elements, I could be wrong on this. It's been about 101-106F here the last weeks or so, so I haven't been killing many frozen paintballs(too hot on the back porch), but I suspect they don't last long in this sort of heat. I think I mentioned in a previous post how I stab them with a toothpic prior to freezing so I can prop them up in a piece of styrofoam, I think the hole is so small and tight around the toothpics that they don't leak much and wont just fall off. The frozen part just makes them come apart more when they're hit, when my son hits the non-frozen ones with his Red Ryder they go through sometimes without a wimper.
I usually shoot with my trap right at ground level more or less, I have close by neighbors and can't really be shooting over the fence. behind my back fence however is a drainage canal, so if I shoot at a slight slope and something goes past the trap they are at least heading toward the canal. So far no unhappy neighbors and they all know I shoot back there.
We have some scrap galvanized steel at work I've been eyeballing, think I might use that as a deflector plate. Friend of mine also offered up an old car, yes an actual autmobile. He said I could come out with my sawsall and lop a chunk out of the door or hood to use as a deflector...we'll see:)
Dan