No, not James Bond deflecting a lead bullet with a fancy watch but a silly idea.
Small powerful magnets have become relatively cheap over the last few years. So what would happen if several stacks of mini magnets were loaded into a shotgun cartridge? Would they stay together like a shotgun slug and then break into separate projectiles upon impact? Would the high speed magnetic fields going down a steel barrel create extra resistance to the movement and push up pressures?
I think someone should try it (I have no shotgun).
The small, squat cylindrical type, just under 1/3 of the diameter of the inside of a shotgun cup might work. They would have to be weighed to match an equivalent steel shot load.
BB