Re: 260 Brass Forming
When I am at the range, I pick up any 308 cases I find laying around (mostly Fed GMM cases) and then turn it into plinking brass for my 260. Turning 308 brass into 260 brass is a lot of work. First, I FL size the brass in a 308 die. Then I turn the necks of the cases, but you can not turn them all the way to the shoulder, you have to stop 3/4 of the way down the neck. Then I FL size with a 7-08 die, then neck size with a 6.5 mm neck sizer. If you turn the necks of the cases all the way back to the shoulder when it is a 308, after they are sized down to 6.5 mm, the location of where you stopped neck turning is now on the shoulder of the case. So stopping turning 3/4 of the way down the neck puts the end of the neck turning at the proper shoulder location once they are 6.5mm.
The first lot of brass that I tried I did not neck size the cases, and in the end, I threw the cases out. The necks were so thick that once loaded, the outside diameter of the neck was larger than the chamber dimensions, so the rounds would not completely chamber. I tried to turn the necks, but they are so thick and work hardened, it was close to impossible. The real solution would have been to anneal the necks and then try to turn them, but I do not have a annealing machine, and that seemed like way too much work for plinking brass.
After doing this with about 400 cases, I gave up. I do not feel it is worth all the effort. For my match brass, I use Win 7-08 brass necked down. Or Chad has a very good point, Lapua is now making 260 brass.
So yes, it is possible, but it is a lot of work.