If you are building an artillery piece, maybe you should build a system that would prevent fire below a certain level, as said by
Originally Posted by tunabreath
To prevent direct hits, the launcher can have a safety gimbal that would prevent firing below 45 degrees or something.
As for the ammunition it self if launched as an inderect fire, you could insert a parachute to slow the fall of it either all the way down or low enough to let it fall freely at a safe speed for its weight. You could also include in the ammunition a system that would make it "detonate" so that it spreads BB all over an area. This last system, combined with a parachute would render the ammo pretty much safe, don't you think?
I know this seems complicated but for safety sake I believe it is doable.