Your own explosions kill you as if you dont even have the perk. Try it by throwing a semtex against the wall. At full health you should survive no problem, even touching it because it's not a stick. But if it's your own, you can be a good 1-2 meters away and still die.
It's kind of annoying when an enemy walks by my betty and it kills me at full health, even though I had the perk on.