I have Redding dies and it's quite an easy process making the brass with one pass.You won't tell any difference between in necking it down and just resizing a regular case,same with necking up once-fired 7mag cases.I think the die does have a vent hole under the nut.I do have Norma 308 Norma Magnum brass I bought from Bruno Shooters Supply,but I have to reduce my loads a little because that brass is a lot softer than Winchester or Remington brass.If I don't,my primer pockets can get loose after the first firing.I guess it's a good thing in a way,at least you know your pressure is OK.I've never had an issue with loose primer pockets an any brass other than the Norma.

~Molɔ̀ːn Labé Skýla~
As Bob Hagel would say"You should not use a rifle that will kill an animal when everything goes right; you should use one that will do the job when everything goes wrong."Good words of wisdom...............