I'd try a different choke. I'm partial to a PG .570 and Nitros but get ok results with Hevi 6's and 7's with that choke as well. I don't get anything near what others are with either one but 100ish to 40 with the 6's and 135ish with the 7's. I like the .555 PG as well but both chokes are actually quite comparable out of my 1187 so I've always hunted with the .570.
