Back in the day, ammo makers would do a lot if you asked them and had a friend in the right spot. My father and a couple friends had a island in the Chesapeake Bay, which they duck hunted before WWII. One friend, the owner of the local Ford dealership, ordered shells loaded with number 5 shot for early ducks and number 3 shot for late season ducks. At the time #3 was not standard fare, that was #2&4 shot. I think he ordered 1 3/8 ounce #3 or it could have been 1 1/2 ounce. His shot and payload was not standard fare but they loaded it for him. He ordered five cases of each, every year, and those cases were 500 not our 250 flats. How I wish I had one of those wooden crates that ammo came in.
The island is now part of a refuge after being gunned for 60 plus years in my family. Family lore states that thousands, maybe tens of thousands of duck were killed there and if you started a fire near the sore blinds, whiskey would boil up out of the water. Back then baiting was legal, in my youth you could still bait as long as it was 500 yards away from your blind. And bag limits had declined from 25 to 10 ducks per day, which many men ignored on a "good" day. There was only one state game warden and he drove a Ford.