I have not shot the 12 gauge SST, but I have some for my 870. However, the 12 gauge SSTs are 300 grain and if you go to the in-line muzzleloading forum, you can find discussions on the bullet's performance. I actually just inquired about the same thing in reference to the bullet. I am using 300 grain T/C Shockwaves this season in my muzzleloader and that is what the Shockwave bullet is, a Hornady SST-ML.