Don't forget forget weather conditions, wind speed, temp, some powders are affected by heat or cold. Have had loads that i tested in warm temperature (75 degrees) and all shots were touching and when the temperature dropped below 50 degrees, the group opened up to over 2". So i made a personal rule to only test loads in the condititions it will ammo be used in. Deer loads test in cold weather and varmint only in warm weather.