USE Precision scale weight sets,a lot of scales have a 20 gram/308.6 grain scale weight,you use them to Zero your scale.and put Precision weights on and find out your scale is off.Lyman and other Company's make them ,relatively cheap.What ever you are weighing,Example-you want to way 44.3 grains,u put 44.3 grains of the precision weights on your pan,zero it take them off put them back,it should read 44.3 grains.What ever the weight is your trying to measure.They have .5,1,2,5,10.20.50.100 grain precision weights.You can check EXACTLY where your scale is.If your goal is The most accurate Shells you can Get,the Check weights are the way to go.I just got another 1000 40 grain bullets,i sorted by Ogive length,and weighed them.To my surprise i had bullets that weighed from 39.4 grains to 40.2 grains, They shoot to different POI and the lighter ones usually don't group as well.I,ve had multiple bullets in different calibers, that when weighed were off.At one time or another most people WILL wind up getting bullets that do not weigh what they are supposed to weigh.If your trying to drop powder charges to 1-2 kernals of powder,ya can't when your scale is off.If you are using balance type,digital,etc,the scale weights are #1.I have been loading since the 60's,have seen scales stop working,start fluctuating,ETC Shit Happens,If you have Check Weights,At Least you will know what happened Before The Boom. lol