For a Sig.357 load you may try and like using a .355 Dia and .147 grain 9mm Bullet and using some 8.0 blue dot powder it will travel at around 1200 mzl vel. I also like starline brass. of couse w use small primers.
I have switched to 13.3g of no.9 behing a .355 hornady jacketed flat point and using starline brass with cci small primers. It seem to work nicely but has a bit more recoil than the unique load. Accuracy from the unique load wasnt very good due to extremely low velocities.
I also loaded up a few 14g no.9 loads and they are fun, high recoil and huge muzzle blast get everyones attention at the range.