Longbow, I have the Stevens 301 in 20 ga and handloads of TSS #9. That factory choke in my gun is a 575 constriction and throws a great pattern. First of all, you need to clean it real good and it took me a while to do it. After you clean it, put it away and check next day you will probably find residue in it still. Clean it again.... check another day....keep doing this till you can push a cotton ball down it and it comes out perfectly clean. Then you ready to shoot. I also have a REM Fieldmaster 20 ga and it gets the same treatment. The Stevens throws 305 in the 10" and 176 in the 20" for a total of 481. The Fieldmaster with a Carlson 575 throws 299 in the 10" and 189 in the 20".....488 total. They both put 47 and 53 in the head and neck vert. Until I cleaned them the way I described was waisting a lot of shells and money. Both these guns like a clean barrel. I loaded up some # 9 few days ago with Hal Abbott and he told me they would put 300 in the 10" if the barrel was clean....so take it for what the expert says. Let up know what you decide.