I just put the most major ones but yeah, Knights Arament produced the SOPMOD Block I's RIS, the foregrip, and alot of other rifle related accesories, and the SOPMOD Block II features rails from Daniel Defense, not to mention the sights (Eotech, Aimpoint, Trijicon) and then laser tech (Insight Technology). Pretty much everything is from the private sector, hardly anything if anything at all is produced by the government.
I don't think Bushmaster has any contracts with the Department of Defense though and I'm pretty sure that Colt has the only contract for M4/M16s.