Re: 6.5x55 brass from 270
I like to see guys like you thinking you way through a situation. I've been there too, but your situation is more radical than mine. I would have opted for 6mm rem or something closer, but it shows that you can make it work with what's on hand.
I use .308 Military LC Match brass for my .243 Ackley improved and I am right now preping .270 brass to become 6.5-06 Ackley Improved brass.
You're basically "wildcatting" exhisting brass for a factory chambering. Just like I've seen an older fella make .348 Win Brass from 45-70 Govt brass.