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jellyhead .655 and hevi magblends or str.7's.
Id go indian creek and mag blends or str.7's
Try a Jellyhead. Works for me.
I love my .670 rhino w heavy 13 magnum blend
You didn't mention which barrel you have. I have 2 391's. One has a optima barrel and the bore is .732 and I'm using a PureGold .670. The other has a Mobil barrel .723 with a Indian Creek .665. They both love the 2oz load of the Hevi 7's. I'm using the Hevi 6's this year, while good, its not like the 7's which has a lot more shot. But in general you will need a little more open choke in the optima barrel. Any of the name brand or custom made chokes should be fine. I guess we all are assuming you have a 12 GA.