I'm wondering what is the optimal distance for chronograph to be from the muzzle in order to get the most accurate readings without damaging the unit from muzzle blast? And will a muzzle brake change the distance at which you place the unit? I only ask this because my only experience using a chronograph is with a buddy of mine and when shooting rifles he sets up unit about 20 feet away. Is this neccessary? I feel that is to far to get an accurate reading on MV. What do you guys think?