Rick you said use 300 win mag brass , why not 358 norma brass, is that due to the cost or what?
You might be sorry you asked.
One reason is that Norma brass is typically very soft.
The second reason: I wrote this for a friend a few years back, and was smart enough to save it. Doesn't mean I'm right, but I have been incredibly impressed with the resulting cartridge.
Here's another option for you, and the way I went when I had a 358 Norma built about 5 years ago. I had the neck reamed out to a case length of 2.61". This was accomplished after standard chambering with the 358 Norma reamer, by then running in a 35 Whelen reamer with it's longer case neck, to the 2.61" chamber length. Why?? This lets me use untrimmed WW 300 Win brass. Just a pass through the FL sizer with well lubed case necks, and the brass is ready to go.
I use standard FL dies, in my case Redding, which work fine. The sizer die works exactly the same way, although I had the expander ball tapered more gently to make it easier to neck up the cases. To set the die I simply kept screwing the die into the press bit by bit, until the 300 cases had the shoulder pushed back far enough to fit the chamber. This works fine for resizing the fired cases as well, of course.
The seater die has to be backed off a bit, and the bullet seating stem screwed in farther to compensate. Otherwise it would crimp the case neck......a lot.
My motivation to do this was to use the 300 Win brass with the longer shoulder. A lot of people use the 338 Win brass, but we all know the shoulder is shorter on 338 Win brass. I didn't like the idea of fireforming brass by blowing the shoulder forward, hence weakening the brass. It made more sense to push a shoulder back, maintaining positive headspace while fireforming. So I thought, seriously, about using WW 300 Win brass, then trimming about 1/10" off the resized case, which made no sense. Then I hit upon having the neck extended so I wouldn't have to trim the hell out of the new brass.
It just makes more sense. With the longer neck, more of that long bullet is held under tension, just improving on the original design. It lets me use the inexpensive, great quality WW 300 Win brass, instead of buying the much more expensive, and historically soft Norma brass.
This was my only complaint with the original 358 Norma case design, in a mag action with room to spare, why saddle it with that short neck? The new case can be described as a 358 Norma case with a 35 Whelen neck, really the best of both worlds. If you do have this done, all it takes is running a 35 Whelen chamber reamer into your 358 Norma chamber. The shoulder/case aren't affected, just the neck is lengthened. Just be sure the neck dimensions of the reamers are similar, Norma neck dimensions are notorious for being on the "large" side. My chamber has a 2.6" "trim-to" length, with a max length of 2.61". This lets me trim the newly sized-up cases just enough to square the case mouths, instead of spending hours trimming.
This also lets you use 358 Norma factory rounds, it's essentially a freebore with those. It's such an obvious improvement to the standard 358 Norma case I can't understand why everybody doesn't do it!
I have picked up a bit of case capacity. With 250 grainers I get 2800, but my standard load is the 225 TSX at 2950 fps. Let�s just say it �impresses� game, and shoots really flat as well.
