What affects extreme spread and standard deviation the most in a load, powder or length. Most of my 100 yd. accuracy loads have high ES and SD numbers, i.e. 80ES 36SD. I want to tune the loads so that they have low ES and SD numbers. Will overall length make a difference, or should I focus on how much powder I put in, or do I have to use a different powder. I want to get my .308 win. below a 20fps ES. Thank you.