I shoot all my test loads from a rest where my gun has been strapped down. That way I am taken out of the equation. With me taken out of the equation (except for the trigger pull), I can see what a particular load will do in my rifle. Once I find a load that I knows does good in my rifle, then I start shooting it holding it myself. Then if something is off, then I know it's me, not my rifle or the load I am shooting.
That's just what I do. I like to take as many things out of the equation that could possibly mess up the shot.