RE: Turkey choke for a Mossberg 500?
IMO if you are shooting a .660 choke I think a Winchester Supreme 13/4 oz 3" #6 or #5 will shoot the best
I also have a MB 500 with a .665 choke and the Whinchester 3" super X #6 will put 39 pellets in the head & neck @ 40yds .
One thing you have to watch is if you get a choke that is to tight alot of times your pattern will self distruct after 15 or 20 yds spredding out way to fast or it will hold so tight of a pattern that it will act more like a slug at closer ranges and it will be very easy to miss at 25yds or closer.
Ron