30 grains of HS6 behind an ounce of #8 shot works great in my S12. So too does 30 grains of HS5.
The only other reload I have tried is 18 grains of Bullseye behind an ounce of #8 shot. It failed to reliably eject.
I would be interested to see if anyone has a Bullseye, Red Dot, or Herco load that works well in the S12.