Matt's spot on, as always.870 with an M4 style stock and grip. I've never seen one with a rail like that on it, but I'm sure Google could turn something up. The sight appears to be an Eotech.
You might try asking the person who's avatar it is.
I get tired of Googling stuff for others at times. I don't know how people aren't savvy to it yet. I wouldn't have made it through college without Google.
actually the pic is from sjhardware.com and costs 219.00That might be the rail but the pistol grip and stock setup looks like a mesa. You can get three different versions of their pistol grip stock. High, low, and leo. The high and low have their own versions of a rail that is shorter and lighter. Midwayusa carries them. You can get a full setup for around $200 or $250.