The MR223/MR556 are the only civilian available rifles that 'match' the HK416.
Although if you have DEEP pockets, you can purchase a 10.5" or 14.5" HK416 upper receiver, then use a factory MR223 lower (or another lower, as most AR15 lowers are pretty much as good aside from the "safety on when hammer lowered" feature) to complete the rifle.
What purpose do you have for a chrome lined barrel? Unless you're shooting corrosive ammunition through it and not cleaning for a week, or firing in full auto on a regular basis, chrome lining is actually a hindrance to accuracy.
I believe the MR223 has a Nitron coated barrel which for protection sake is equal to hard chrome but without the adverse affect to accuracy.