Okay thanks, I ported the code for making effective the explosion against all present players, and it perfectly works.
The last thing which doesn't work is the blast circle effect, and the explosion is not appearing as well, only some sparks show theirselves.
I at first, supposed that the blast circle was burried in the ground, but when shooting on someone in the air, it didn't appear.
I'll try to fix it myself, and to keep you informed on my plugin's state
Edit: nevermind, I've though about it during school,
here is my problem, thanks anyway and sorry for asking foolish question.