Raimey.
The 6.5x70 R cases take a lot of swaging and drawing out to get them as small as they are. This work hardens the brass in the body of the case pretty severely. The cases were annealed to below the neck, but seemingly not low enough (manufactures are leery of softening the heads) to prevent the splits you experienced. You will not be able to hold the cases in your bare fingers long enough to reach your target area of annealing. A possible, although slower, method of annealing the area you are interested in, is to put them into a pan of water deep enough to protect the heads and tipping them over with a rod after heating. Once you get the procedures worked out, you can speed it up by working in batches and having one of your boy's turn them over while you heat the others. It will benefit them to learn how and why we anneal, anyway. Good luck.
Mike
