wrote this in notepad, i think i should work but even if it doesnt i guess it gives the idea:

VECTOR tmpv;
vec_diff(tmpv, muendung.x, camera_target.x); //tmpv's now the vector from my.x to target.x
vec_normalize(tmpv, 1); //increase length by "1"
vec_add(muendung.x, tmpv); //add that to the target

c_trace(muendung, camera_target, IGNORE_PASSABLE); // trace from muzzle to target

goodluck