I saw a video about an Englishman who was on a punt gun. Apparently, it was still legal when the video was made. It was difficult to get up on a flock without them flying. I don't know the range of the gun. IIRC, instead of shooting them on the water it was desired to shoot when the birds just began to rise as there were more targets exposed. The gun was a muzzle loader, of course. A lot of sneaking up on ducks for one shot only. A slow process.