[4runnerman]

Snuffy- Yes build up in a case can become a issue. They did a test about 2 years ago. After firing a 6BR case 7 times they found that case compactly was down from build up in the case as compared to that same case when it was new. Now how much increase in pressure that amounts to I don't know. But yes it is a fact that your cases will retain build up inside and tumbling in media will not remove it. For a Deer hunter- No big deal, For a Bench shooter, Big Deal being most bench loads are at,near or over max loads.

The reason is: maybe by not tumbling, will you see a difference?.... Probably not. But, do enough little things and they add up to something larger. I.e. a noticeable improvement.

Serria 280 hit it right there. They say each step done can improve accuracy 2 to 3 %. Nothing by itself, but total them all together and now you have something.