A rare earth magnet will find all steel shot easily. Drop the magnet into a 3/4 full bottle of shot and shake it or roll it for a minute. Then pull the magnet out. If there is any steel shot in the bottle it will be stuck to the magnet. Repeat if needed but I never have needed to do it twice. Total number of steel pellets recovered to date is less than a dozen. In the real world the chances of that few number of pellets causing a real problem is remote. I have loaded about 200 pounds of reclaimed shot so far with no problems.
