Case weight shouldn't vary more than 1% for a batch of cases. You'll get a greater difference in accuracy by shooting a rifle whose bolt face hasn't been squared with the chamber (never the bolt) axis. Most primers will show a bigger difference than a 1% case weight spread. Case neck tension can also cause a difference.
In other words, get concerned about case weight uniformity after you can keep all of your shots inside 10 inches at 1000 yards.