With great power comes great responsibility...
The item you're talking about has a massive explosion radius of 20, yet its firing range is 24, so as long as you're at least 21 spaces away from your target, you can't hurt yourself. Of course, that would mean you'd have to stand far, far away from them. You should be able to visually see the explosion radius if you're about to fire your weapon (like any other launchers).
It's also a guided launcher, so you can hide behind walls and set waypoints to fire around corners.
Unfortunately, the weapon is one-time use only, so you only got one shot with this!