This is an M4 upper (model SPC-A3), made completely by Troy Industries. The medium heavy barrel is 16", chambered in 5.56 NATO with a 1/7 inch twist. The chamber and bore are unlined for match grade accuracy. The well-designed muzzle brake reduces muzzle flash as well as reduces barrel rise. There are 2 rails added to the bottom of the M-lock handguard, with multiple guard slots filled in with rubber spacers. The upper is slightly used, as the owner wanted to go with a longer barrel. You can see in the pictures that the condition is like-new.
A new BCG and CH are available for $100 more.
Other AR parts available upon request. See pics for some things available. Not everything pictured.