Boy, talk about a long time between posts. /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif Welcome back.
The 7RUM necked down to 270 and with the shoulder sharpened and moved, and the case sides blown out is the 270 Allen Magnum. I've done a few hundred of them as have others here.
You can do a search on the 270 AM and read all about it or ask Kirby Allen ( fiftydriver ) about it. It's his creation.
If you're just talking about necking it down and leaving everything the same, then I can't help you with that version. The act of necking it down is a simple one step process however, and it goes smoothly. Never lost a case yet.