Unless you swap optics between AR's and bolt guns, the picatinny rail that's on your upper receiver is the only base you need, just get the correct mount.
What rings give you enough forward placement of the scope to get proper eye relief on an AR?
Mine sit at least 1 3/4" - 2" ahead of the charging handle.
Off the top of my head, ADM makes one, the Recon X. LaRue makes one also, the SPR-E. There are others but those two are the ones I am most familiar with.
The standard Recon and SPR mounts have worked for me though. I haven't found a need for a extra long one. Most of my optics sit just forward of the charging handle with a standard AR LOP.
