Chrome-Lined Bore
A barrel bore plated with hard chrome for corrosion resistance and longer service life, at a small cost to outright accuracy potential.
A chrome-lined bore carries a thin layer of hard chrome electroplated over the bore and rifling. That plating resists corrosion, eases cleaning, and slows the throat wear that otherwise ends a barrel, which is why it shows up so often on military and high-volume service rifles where sustained fire is the design priority.
The tradeoff is dimensional: the plating process leaves the bore slightly less uniform than a bare match barrel, so peak accuracy usually gives up a touch. For a precision shooter chasing the smallest groups, an unlined match barrel or a nitride finish is often preferred, while chrome lining stays the practical choice when durability and barrel life matter more than the last fraction of a minute of angle.