Como dizer "Tiro certeiro (com arma de fogo)" em inglês

Depends on what side you are, that is, what you want to say. Wether you are expressing amazement or outrage, etc.

So, some ways to express that:
it was a perfect shot
it was a deadly shot
it was a precise shot
it was one shot one kill
it was a fatal shot

I think it could be said about pretty much of any gun, anyway would be a bit unusual to see someone blowing the top of a gun if the gun is a rifle/shotgun (or trebuchet). Blowing the barrel of a small gun (revolver/pistol) is more to the point.

Ah, if you meant the shot, it can be said of any gun.