How much accuracy do you loose comparing two identical barrels except one has the chrome lining(2 identical M4 style barrels for example)? Let's say at 100 yards. Also, I have heard that the chrome lining barrel will outlast the non chrome lined barrel.  How much longer will it out last?

Both my Bushmasters are chrome lined!
My 20HBAR is plenty accurate! More accurate than I can shoot! I can on good days get ragged holes at 100 yards shooting prone.
I would go for the chrome lined bushmaster barrels! unless maybe you are just going to match shoot?

In an M4 style barrel I don't think you'll notice any loss in accuracy between the chrome and non chrome.  What you will notice is the ease with which you can break in the chrome.  I brought a non chrome barrel which has proved to be very accurate but it was a PITA to break in compared to the chrome barrel on my M17s.  As to the difference in how long they will last, I can't answer that.

This may sound crazy, but what do you mean by breaking in a barrel? I am new to AR's and trying to get all the info I can before I purchase an upper. Thanks

There's really no way to tell.  There are good barrels and bad barrels.  Take any 5 barrels all chrome or all non-chrome and install them identically in the same upper and you will see different accuracies.  So you'd have to do statistical samplings on quite a few of each with enought samples to eliminate variables like weather, installation inconsistencies, shooter, etc.  So you're talking about a lot of money and effort that you'd need to spend.

I've never heard of any manufacturers doing something like this, probably because there is no motivation for them to.  I would suspect that the differences in accuracy are minor and probably negligable compared to the shooter.  

The thing is don't worry about it, a chrome lined barrel will probably shoot better than you can (no flame intended) and will be easier to care for.

CSA_B.,
if you get an upper with a chrome lined barrel, there really is no break in procedure.  I would clean the barrel before shooting and clean again after you're finished.  You might choose to invest in a good, coated (or fiberglass) cleaning rod as chrome or no chrome dragging a steel rod through a barrel ain't good.

When/if you get to stainless steel, match grade triple lapped barrels we can talk again.

There is no 'one' answer as to how much longer chrome lined will last.  Too many variables.  What chrome will allow you to to do is to shoot cheap, dirty, cruddy, out-of-spec mil-surp ammunition without fear of ruining your barrel.

As to chrome lined and accuracy, things appear to have changed in the last couple of years.  ArmaLite AR-10 owners, with the standard chrome lined barrel, are reporting 1" groups at 100 yds.(some are reporting sub 1" groups) - obviously they are using good ammunition when the achieve these results.

5sub

For the most part, accuracy loss will be quite marginal. The fact of the matter is on the standard M4 you have in mind, there will much more preventing you from acheiving the best accuracy out of the gun than a chrome or non chromed barrel. The fact that you dont have a free floated barrel, you will have a stock trigger, and no optics will prevent almost anyone from getting the most accuracy out of a chrome barrel. So switching to a non chromed barrel wont help matters a bit.

At 100 yards, the accuracy difference probably will be virtually unnoticeable.  Farther you go out in range then somethings may turn up.  Depends on what accuracy requirement you need, if man-sized or coyote sized targets are your goal, I don't think it really matters.  If you plan on Highpower or shooting small things far out you will be better served with a SS barrel.

Get a Bushmaster Chrome lined barrel

A free float Diemaco C8 chrome lined barrel is capable of sub MOA.  That is pretty impressive.

I can get consistant MOA out of my Colt 14.5 M4 barrel with Winchester USA white box.

I contacted Bushmaster about this very topic before purchasing my 20" Bushy with a stainless steel barrel.

They said that the croming process has a distinct effect on the quality of the rifling and grooves. They claim that rifling on their stainless steel barrels is much sharper, and therefore can tremendously affect long range accuraccy.

Thats all i can remember....but it sold me, and I couldn't be happier with my decision.

No flame intended but thats what one can expect from most manufacturers.  They didn't by chance provide you to any links or anything objective did they.  I doubt that there's 'tremendous' differences, any exactly how much of a MOA difference is tremendous.  The 600-1000 yd shooters probably see something of a difference but they're using premium barrels anyway.

I like bushmaster but they got the marketing thing down (not that there's anything wrong with that).

yeah, they mail you a new catalog with every purchase, which is very tempting to look through....

That's why cleaning rods are aluminum.  That way they are softer than the rifling they come in contact with.

Until you have a sectional aluminum rod break.  Aluminum is softer than steel, but you can still make a very good gouge in the rifling when the (weak) aluminum rod snaps when pushing a tight patch through.  Take a piece of aluminum and swipe a sharp edge of it across a piece of steel.  The aluminum deforms more, but the steel will have marks, too.

As far as accuracy on Chrome/Non-Chrome:  If you are shooting at 8" target under 200 yds, you probably wouldn't notice the difference in an M4.  Barrel length, non-floated, sight radius, etc. are affecting your accuracy more than the bbl. If you are wanting to shoot smaller at longer ranges, you probably don't want an M4...

Chrome is great to keep the barrel from rusting when carried in rain, easier to clean, but the downside:  The Chrome lining does wear off.  After a few thousand rounds, you won't have a lined barrel, at least near the throat, especially if you do a lot of rapid-fire.

Chrome loses accuracy mostly because the blank has to be cut a bit wide on tolerance to make room for the 0.00075 - 0.002" layer of chrome plating, which isn't always perfectly even or exact.  A triple cut/lapped steel barrel will have exact diameter entire length with no irregularities.  

I will now put on my asbestos suit.

FN makes a sniper rifle in 7.62x51 using chrome lined MG barrels. They reject 98% of all the barrels they test because of irregularities. At 100 yards you can find accuracy differences from none to three times the sub moa my target rifle will hold. I do agree that the accuracy difference can magnify itself at greater ranges. Some of my rifles really open up past 200 yards, some not so much.