There is a pretty big length difference. About the same as a 300 weatherby to a 7mm weatherby (almost a half an inch). The 7mm stw is the 8mm rem mag necked down, a 257 stw is going to be a powder hog, now and then I shoot a 6.5 wwh which is a 300 weatherby necked to 6.5. That uses a lot of powder and likes to get barrels hot so I think you are in for a barrel burner.
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