.555 jebbs in my 20ga 870 was mid 130 in the 10" @ 40yrds
The cheap .570 promos did a tad better...mid 140s
Ive been reading a lot on here about the .570s being a better go... for the numbers anyway, both for 9s and 7s.
I like 7s so ill likely never shoot 9s
note: i didn't shoot at 20 so I'm wondering how tight it'll be, may be too tight for my taste.