Was firing some 30-06 (IMR 4831 53.8 grains)/220gr Hornady RN loads; average ~2400 fps. I noticed the brass coming out like this. The cases also stretched lengthwise about 0.01 inch on average.

Are these pressure signs?

I would say no. Above that line the case is conforming to the chamber, and below it the case head is not as supported and should retain its dimensions after being fired. If the case head is changing dimensions, then that would be a sign of excessive pressure. If you start seeing cracks in that area, the case head is starting to separate, and you should toss the case and perhaps not set the shoulder back as much.

Well that's good to hear. I've got my dies set to push the shoulder back about 0.002 inch, so basically a neck sizing only.

I've never shot this heavy of a load through this rifle, and was getting worried when I saw the brass in this condition.

You`re looking at HotCores famous "pressure ring" if you`re worried about pressure he`ll tell ya how to measure itto see where you`re at

Don`t worry, it is in its self a perfectly normal occurance and is simply the point the thin wall of the case body meets the solid case head. The wall expands and the solid head remains fairly static.