Chronograph distance from muzzle
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?