The Explosive Missile discovery explains clearly that the missile doesn't detonate if it misses (and if I understand correctly, this cannot work as a touch attack unless you use a firearm at close range, what defeats the purpose of the feat as far as I can tell). What about intentionally shooting at the ground instead of trying to hit a specific target ? Does the infused ammo detonate and deal splash damage to enemies around, or does it really need to hit something specific ?
That's a nice tactic that is perfectly valid. The ground is a target and this is not a spell that only lets you target "creatures" or something like that. Of course, this means that nobody will take the primary damage of the bomb, just the splash damage. Easier target, minor effect looks fair to me.