The smoke coming out the vents is odd, should be distributed more, but if it's fake it's a good one.
“I’ve got a download close to original size, 2000x3000, with the EXIF. It looks clean, no obvious dithering, so he probably actually posed, but it doesn’t make him a shooter.”
Yes, I think it is real. It was obviously posed, as you need some decent equipment to catch the shot at the point that the shotgun is recoiling. Several ways to do it, but clearly posed.
This is where I snagged the photo
http://www.weeklystandard.com/blogs/wh-releases-photo-obama-shooting-gun_699234.html
I still think two things are odd. First how no gas is coming out of the ports on the left side of the muzzle, and second how there is no extended choke tube on the lower barrel. you usually would not mix flush and extended tubes.
Where is the smoke plume on the left side ports?
5.56mm