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Anneal the neck after sizing. If you anneal before, there is a possibility for the neck to collapse. If you don't anneal afterwards, the necks will crack later. Polish the inside of your resizing die...

Size the 243 brass only until it will chamber in your rifle. Don't just give the brass total resize treatment which may create headspace problems. I used to resize military 7.62x51 brass for my 243...