I use 4.0 of clays with a 200 gr molly lead bullet in my 21sf. Have tried 3.8-4.3 with this bullet and they all worked fine. I have heard of people using as low as 3.2-3.3 of clays (having to change to a lighter recoil spring to cycle, but this wouldn't work in GSSF since you have to be stock except for unlimited class). Very soft with the 3.8 of clays, might be perfect for GSSF if it cycles ok. I ultimately settled with the 4.0, since I wanted enough to cycle well, but not too snappy like the 4.2-4.3 loads. I don't have a chrono but from what I can gather from others load data this is right around 165 pf to make major in uspsa also if you are going to shoot that any.