I don't think I've seen the USSS with a shotgun, much less a double barrel, since, gosh, I don't know.
Actually, not to get too technical here, but the secret service has many remington 870's ready to go hidden away in their array of vehicles. They are only used close range when there is a minimal chance of hitting a bystander, which isn't often.
I don't always get to the range, but when I do, I prefer dosAK's.
They say 5 out of 4 people are bad at math, but what do I know?