Is there a difference in hard-chromed barrels and chrome-lined barrels for the bore of high-powered rifles? Thanks.

I would expect they are exactly the same, cosmetic chrome finishes like you see on a bumper would never hold up to the pressure generated in a rifle barrel, it would start peeling out on the first shot.

Same thing. All that "hard" plating means is that it is directly plated onto the base metal instead of having an "Understrike", like Copper, as decoratine plating has.

Most hard chromed barrels are plated on the outside only, while chrome lined barrels are plated down the inside of the bore like they did to the M-16's after they had so many problems with them rusting in the wet jungle environment of VN.

The chrome lining in a bore is only microns thick and doesn't reduce bore dimensions to any easily measurable degree. It does reduce drag which in turn ups velocity and eliminates rust and fouling build up.

The FNAR sports a hard-chromed barrel. The M4 sports a chrome-lined barrel. I guess it would be best to call FNH to get a more direct answer, unless someone might know about their bore.....
It is to my understanding the chrome-lined barrels can maintain their accuracy much longer, given the same circumstances, than a barrel that has not been chrome-lined; hence, more rounds fired and longer life of accuracy in the barrel. Any other comments would be appreciated.

Thanks again.

Yes, that's true, I simply forgot to mention that. That was another reason that they started chrome lining M-16 barrels earlier on. It is related to the less friction that I did mention.

Website states the FNAR has a hard-chromed bore. I wonder if it lasts as long without the copper lining underneath.

The chromed lined bores and chambers are done with industrial hard chrome. This allows the gun manufacturer to use a lesser grade of steel for the barrel since its not seeing any wear.

The chrome lined bores and chamber is done for a longer barrel life and a longer life in accuracy too.

Some of the sks's and ak 47's have between 100k to 200k rounds through them and there accuracy isn't like new but still decent.

Hard chrome is used in rifle bores. There is no need for the copper and nickel undercoatings as on "bumper chrome." Bumper chrome would not last inside a bore. Too soft. The copper coatings makes the nickel coating stick better. It is the nickel that gives the shiny appearance. Bumper chrome has a very thin coating of actual chrome over the nickel to protect it.

M14 barrels also had hard chrome lined barrels.

They actually cut the chambers and bores over size to allow for the thickness of the hard chrome industrial plating. They have to chrome line the chambers too otherwise the lining would chip if they left the seam in the barrel or at the edge of the throat. It's a one step process.
I believe the Russians were the first ones to actually use industrial hard chrome lined bores and chambers. They taught the Chinese how to do the process and at the same time it caught on to the rest of the world. The Russian chrome lined bores and chambers goes back to ww 2 in the svt 38/40 Tokarevs.
It also allows the usage of corrosive ammo too without the dangers of hurting the bore and chambers. The hard chrome in the chamber extends the life of the headspace when using steel cased ammo.

The US used steel cased ammo in ww 2 in the 45acp ammo.

You shouldn't make the mistake of believing that a hard chrome bore is more accurate...no match grade custom barrels are hard chromed and the reason is that they are not as accurate when plated. Hard chrome bores can and often do last longer. The Russians did it for a different reason than we did. They did it because they use mild soft steel jacketed bullets. Most Wolf ammo has copper or brown painted bullets!!! I guess they have better use for their copper. They also use the rifling that is radiused on the drive side {similar to what we call 5R} for the same reason.
We did it to the original M-16's to make the bore faster and easier to clean. Many shotguns have a chrome lined bore for the same reason and it works too...I would a lot rather clean a Benelli than an 11-87!!
Hard chrome bores are also supposed to take more heat {sustained fire} better than one without it. This works up to a point, too hot is still too hot and the throat still erodes. It has also been said that hard chrome is for tracers too. I have fired many tracer rounds in 4150 steel barrels and had no problems or seen any tracer related damage. Bottom line for me is that other than the little bit easier clean up....well, I wouldn't sell a gun just because it has a chrome bore but I definitely wouldn't pay any extra for it and i for sure wouldn't get it expecting the gun to be more accurate.

I didn't say the chrome lined bore is more accurate over a good quality chrome moly steel barrel.

My Russian Izmash Saiga in 308win w/16" barrel will shoot 1 1/2" groups from the bench using surplus south African 308 ball ammo at 100yds. No scope. My Chinese norinco paratrooper sks with a 16" barrel will shoot 1 1/2" groups from the bench @ 100yds. using norinco yellow box ammo again no scope. Both rifles have chrome lined bores and chambers.
My 700 Remington in 338wm will put two rounds of Winchester super X ammO through the same hole at 100yds. With a standard steel REM barrel.

My point is accuracy is what it is when a barrel is chromed but the Saiga will shoot 1/2" moa' s using better quality ammo. The quality of the ammo, plus the accuracy of the barrel and the shooters talents must be considered. Chromed lined bores have come a long way. The Russians did say they focused on making the Saiga more accurate than its ak brothers. For some reason the American calibers of 223 & 308 are a tad more accurate in the Saiga over the Russian calibers. The Russians at Izmash think it's the design of our brass case. After all the 308win/NATO was designed / copied from the performance and track record of the 300 savage.