A friend has a pair of McKay Brown OU's. He shoots typical driven birds in the UK (not the ultra-high ones featured at some shoots), and asked David for his advice on chokes. His guns are .010 in both barrels. Quarter choke, I think, is plenty good for normal driven birds. And for far more walked-up opportunities than most people would think.
In his book, Brister tells an interesting story from a dove hunt in Mexico. Another hunter, watching Brister stone birds with his pump, was having trouble hitting well. He remarked to Brister that the tight choke on the gun--it was marked "full"--must be the secret of Brister's success. So Brister loaned the guy the gun, and indeed his shooting improved significantly. Only thing was, Brister had bored out that long-shooting full choke barrel to IC!
