My godson has a 20. It's only good to maybe just over 30 but that's without a turkey choke. I'm no fan of the gun per se but it's as good as many without tweaking chokes, barrels, loads. He's shooting federal mag shock 6s or 5s I forget. He's a busy young fellow and doesn't live near me so we didn't go nuts getting gun right. Instead we stayed inside effective range. He's used it three times w 2 dead birds. Wish I still had pattern pics for you. I'd think the 12 would be fine especially if messed with to get the most out of it.
Just fyi w the chokes he had the federal was the best. We tried no hevi shot type loads, all coated lead. Nothing below 6s.