Im re barreling my Rem700 and have 400pc of hornady 338 win shot 5 times, they have all been primer pocket uniformed, flash hole de burred, annealed every firing, and partially turned.
The new barrel is criteron 7mag. Ive already ordered 300 pc of new brass but hate to scrap all that good brass.(no signs of thinning at belt , only been fl sized twice.)
I partial size half the neck with 300wm die, then full length size the rest of the way with 7mag die. I measured the necks at .015 which means ill probably have to turn 1 to 2 thousandths. There is only one case out of 20 that ive sized so far with a small crack in the neck.
Has anyone did this before with success as far as accuacy is concerned? ( The one on the right was born 7mag)
What you are describing is done all the time. It is best done in steps, rather than all at once. It is easier on the brass. I shoot a 277 Allen Magnum. I start with a 338 Lapua Magnum case and run it through a Redding bushing die. I first take the case neck down from .338 to .323. Then I neck it down again to .308. I then anneal my brass again before taking it down to .284 and then, finally resizing at .277. Working the brass that much can make it hard, so annealing becomes your friend. You should watch for a thickening a brass at the neck (turning may become necessary). You also need to watch for the "doughnut" - a potential ring of brass that builds up inside the case where the neck and shoulder come together.
To date, I have had no problems. There are a lot of Allen Magnum owners on LRH that use the same 338 Lapua as the parent case for their rifles. They do likewise, and I have never heard anyone having problems necking down their brass.