My wife's Winchester Model 70 Ultimate Shadow Stainless is a collectors piece. They didn't make many, and after looking for over two years, I still have been unable to locate another, so I am severely loathe to make any changes (such as a new barrel), to a desirable item. Unfortunately, the sloppy factory chamber frustrates me to no end. New factory loaded brass ammo measures 0.265" at the neck. A fired case measures 0.274" !! Using the really fancy nickle plated ammo a new cartridge measures 0.2655" (almost 0.266"), and a fired case is right at 0.275". And they shoot better than the brass cases. Gotta do something. SAAMI print shows the chamber to be +/- 0.275", with spring-back taken into account, I think my chamber in the neck area is roughly 0.277" or so. Only a chamber cast will tell the truth. Another challenge is the ridiculously thin pencil barrel used with this high-intensity shell. It could stand to be thicker, but that is another story. So here is what I am going to do: I have ordered a bag of 50 .243 WSSM cases. I will prep them just as I do all my brass, and spend a little extra time to get a good outside chamfer on the mouth. I'll then run a case up into my .223 WSSM die to see if I can squash the neck down without collapsing it. If this doesn't work, I'll use my Wilson bushing sizer and size in two stages. Now that the case will be necked down, I'll run the .223 neck turning mandrel in to make it smooth, and turn to a size about 0.002" under the chamber neck. Then we'll see what she can really do. Right now I can get 1" groups all day long, and an occasional one hole 2-shot group. So I know there is potential here; if only Winchester had used a heavier barrel, the rifle is so light, holding it steady is near impossible. But musing about reality won't change things. Just to be on the safe size, before I get into prepping 50 cases, I'll make a chamber cast to see just how things are.