You may be better served building one. A Mossberg MVP Patrol can be had for around $800, with a 16.5" barrel (not a bull barrel though). The MDT LSS Gen 2 is $400 and the Skeleton carbine stock is $130, or you can get a buffer tube, and MOE stock for around $100, $30 for an AR grip and add the scope of your choice. You could be set up with a nearly identical rifle for $1400 with out the glass.
I have a MVP Patrol and plan on adding the MDT LSS and Skeleton stock. Its a solid shooter and the bolt smooths out after a few hundred rounds. It also take 10rd AR10 pistol mags.