During the times I weight my cases, I did find a great variance in case weight and a greater amount between manufactures, and even as much as 15gr with the same manufacture. It did help in my SD, but not as much as I would have liked. My groups did improved to about 1/2". That's when I called it good and my cold bore shots were dead on too. That was a must with me, because I hunted in greatly different weather. -20 to 110+ temps. I also changed my powder to mostly H4350. It one of the best for not changing much in temp variances.