Not OP IMO, because that's what a tranq round is supposed to do and does in every game, which is knock someone out instantly. Of course tougher enemies could have some resistance to the chemical the tranq injects causing you to have to use more of them and I wouldn't mind seeing that too. We know exactly what's causing the explosions. It's a secondary feature of the Projectile Launch System itself. Take a look at the description for the PLS and you'll see it. Apparently the game applies this effect to all types of mods for the PLS and it really shouldn't in the case of tranq rounds which are supposed to be a stealth option. This is why I suggested the devs could create a Common version of the PLS that doesn't have this secondary feature. I suspect there are several ways the problem could be solved. I would not mind if someone just created a new weapon with regular tranq darts, perhaps a pistol and sniper rifle version like is found in Deus Ex Human Revolution. That may be an easier way to solve the problem and no one would have to fight with trying to modify the PLS.