The argument about chrome lined vs non chrome lined is ridiculous when talking about a accuracy in a fighting style carbine like an AR-15. The difference is so minuscule (if even existent) that most shooters will never see a difference. We're talking about a semi auto 16" carbine, not an Olympic style match rifle. The service life is going to far surpass that of a non chrome lined one, especially if the shooter plans to really heat it up or put a lot of rounds through one.
^^^^^^This