I just got the 930 this year. Factory choke .670 did fine with XR #5.
I got an Indian Creek .660 and that's even better. I did shoot some custom Nitro Heavyshot. the pattern was low and left with the IC .660. I've never seen a POI change that bad with changing choke and shell combo. XR was on the money. The Nitro I was shooting called for a different shell and choke combo.... Just found it odd that it changed so much. If it stops raining I might try the factory choke.
If you have a brand new gun. Take the barrel off and look at it. Mine was ruff and had machine marks in it. I did a polish job on mine.
Also if you are looking for a custom choke... Call William at Sumtoy.
Keep us updated.