For a long time, everyone and their brother wanted a chrome-lined barrel. They’ll pay extra for it. They’ve heard it’ll last almost forever. They’ve heard it’s the best barrel that ever existed.
And they’re only partly correct.
Chrome lining can protect the barrel from heat and pressure. That’s true.
A good chrome lined barrel can still last for 5,000 rounds before you see any degradation. Maybe more.
However, chrome lining can be uneven in barrels, depending on the manufacturer. The barrels can be SLIGHTLY less accurate than a non-lined barrel (you ARE lining the rifling inside the barrel and therefore there is a slight coating over the lands and grooves, dulling them ever-so-slightly.)
Essentially, chrome-lining is one of those leftover processes that “a guy at the range heard from his buddy at work that his dad always told him…” that chrome-lining was the ONLY kind of barrel you’ll want/need.
This is not to take away from chrome-lined barrels. Like I said, they protect against heat and pressure in an AR. It’s not to say that there are zero benefits to using one.
But there are a LOT of other choices when it comes to barrel treatments. See also Meloniting, Gas Bed Carborization, and Cryogenic Tempering
The Meloniting/ Salt-Bath Nitriding (also called QPQ) process heats the barrel or bolt carrier group to 1100 degrees by dipping it into meloniting salts in liquid form.
This process and the lower temperature being used is dramatically reduced from the standard heat treatment process, giving less chance of warping the barrel, less damage to the steel.
Compared to chrome lining, the meloniting process is both a superior process and cheaper.
And talk about corrosion resistance! You could feasibly throw your barrel or bcg in ocean, come back a year later, and it will still look the same! (Please note that we did NOT just suggest that you throw your AR in the ocean).
Meloniting also gives the barrel or bcg a Rockwell hardness of between 68-72. Read: that’s stinking HARD! It’ll last longer, it’ll be easier to clean, and reduces copper fouling.
You can fire in excess of 15,000-20,000 rounds without seeing degredation in a melonited barrel. (Remember how many round we said a non-treated barrel could shoot earlier? Told you there’d be a test!)
This can double to triple the service life of the barrel. Your grandchildren will shoot out that barrel before you do!
Note: You cannot melonite a chrome-lined barrel or bcg. The chrome and melonite salts have a violent (read: explosive) reaction to each other. We’re trying to increase the life of the barrel, not shorten it!