I'm probably going to take some heat for this, but I have officially crossed over into the camp that believes that tumbling live ammo is no big deal. The reason for this switch is the last two shipments of Greek HXP .30-06 I received from CMP. Both batches were on the older side, especially the shipment from December. It was primarily 60's vintage, and while it had the usual age tarnish, it also had a somewhat tacky feel to it. As if sitting in one place for decades had attracted a muck to the outside of the cases. I'm probably being a mother hen to my pristine Garand, but I wasn't totally comfortable running it through. So I went searching for info, and ran across this piece posted a few years back on ar15.com: Tumble live ammo Tumbler O' thruth EXTREME edition, 200hour torture test**UPDATE**fired rounds in OP - AR15.COM This guy did an extreme torture test of tumbling live ammo for 205 hours. He used a microscope camera to record the pre and post test results on the powder itself. Well, I'll let you see what he came up with and decide for yourself. Suffice to say, the HXP ammo I've tumbled is now clean as a whistle, and the tacky residue has been eliminated. I'm pretty sure they'll all go bang.