357 sig has a straight taper, with angular transitions along the neck. Similar to 30-06, or most rifle cartridges.
The 9X25 has radiused corners along the shoulder. Similar to the weatherby magnums.
If you purchase a 357 Sig reamer, and ream your barrel, you will have a true wildcat! It will be very similar, if not better than the 9X25 in performance, but dies will be much cheaper! You would just need to experiment with your headspace when you form and reload your brass. To get it right, you won't be able to crank your 357 Sig dies all the way down...
What are you going to call it, the 357-10? 357 9X10? Sig mag? It would certainly keep up with any 357 Mag revolver using the same length barrel and bullets less than 160 grains...
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