The wsm and wssm cases have been taken all the way up to 458 and even a straight wall 50 cal of some sort.
There was a 25 wssm at some stage. Neck up to 6.5 was also a nice concept for something that was a bit less of a barrel burner. The problem is finding brass to feed the thing.
If you have the money and the patience everything is possible I guess.
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