I have been hunting with a 870 with a Primos Tightwad choke and shooting Nitro Blends of 4 x 5 x 7s. This year I bought a Browning BPS 12 gauge lnvector Plus and was looking for some first hand experience on choke and shells(prefer Nitro).
Lot of chokes out there that are good. I shoot a .670 rob roberts. It shot 4x5x7's nitros pretty good. I'd look at nitros website like Arkrem said or call rob roberts and talk to him. You'll be hard pressed to find someone who patterns more and different loads every year as him. Jmo for what it's worth
I shot a Kick's Gobblin Thunder out of my Browning and I still shoot one on my Remington Super Mag. I used #6's and it was deadly to 50 yards, wouldn't shoot one past that, too many things go wrong after that distance.
Jelly head .670 with 3 1/2 nitros is devasting. Haven't stretched it out, but it will literally "jelly" a head at 30- to the point of almost severing. I shoot a maxus. Have killed 6 Arkansas birds with it so far and it patterns a lot better than magnums and .660 jelly head with my 870.