The SST shoots great out of my H&R 20 - Love that Gun! I'm not happy with SST in any 12ga(another story). I would not recommend the SST 20 without having 1st shot at least 5-6 rounds - I have.

When I research this site for - any - info, I read all the info,give a grade,add a grain of salt and go with it.In this case,at least try a box of SST's along with maybe 1-2 other suggested brands. Getting any "Slug Gun" Tuned In Ain't Cheap!
Keep the Barrel Clean and Cool between shots! Try to duplicate your actual field conditions(I.E. time of yr,single shot gun,clean,cool barrel etc...etc.). Clean barrel every 3-4 rounds.I've shot these miserable ugly slug slingers for over 3 decades and found a "Clean Cool Barrel" is the best way to find the best round/accuracy.

Good Luck