I know the bolt and other parts in the carrier eventually wear out and need replacing; but does the carrier itself ever?

Only if breaks or gets worn beyond specs.

Any idea what kind of round count that would take?

It would depend on some other factors....suppressed, what rounds are being fired, how often are cleaning/lubrication intervals...


It should be several thousand rounds, to say the least....in other words, have spares but shoot until you see an issue.

Moving parts in anything wear out eventually.

You will most likely wear out many barrels before you would even need to consider replacing the carrier if it is a decent quality one.

I have an Original early sixties Colt Hard Chrome plated carrier and it has worn quite a bit of the chrome off.

It still runs perfect.

Keep it mind too that the carrier being steel rides on aluminum tracks in the upper receiver. Aluminum being the softer of the two metals will act like a self-lubricating bearing surface. Also, being aluminum is going to wear first being as already mentioned the softer of the two metals.

I've seen bolt carriers crack but I have yet to see a quality carrier wear out. I think the area most prone to wear would be where the gas rings slide back and forth in the carrier. Like said above, you more likely to go though several barrels and a shit ton of ammunition before it would wear out. If you can afford to wear out a bolt carrier, replacing it is inexpensive non-issue. I keep 1 spare carrier and a handful of spare bolts I have picked up here and there over the years.

As stated above, I have been around AR's ever since the early 90's and the only parts that I have ever seen wear our or fail on bcg's are gas rings and improperly staked gas keys. I have never known of an bcg needing to be replaced. IMO, bcg's are like fine wines in that they get better "smoother with age". Dad has a 1977 Colt SP-1 and it has the smoothest action that I have ever felt.

Carrier:
Wear out, not so much, but must at some point.
Break, some do.
Crack, some do.

Gas key, yes, but how fast depends on gas key alignment.

+1

IMO, you're more likely to have to replace your upper receiver before your carrier (assuming the carrier is well made).

This

The carrier itself...not likely.  However, the gas key could wear out/break over time.

This.

Google "Filthy 14", a BCM rifle which went just short of 29,000 (yes, 29K) rounds before they cleaned it and last I saw (>a  year ago) has over 43,000 through it.

2 bolts, original carrier.

except for that pesky coating we call aluminum oxide





 

probably around 1 million or more (not counting breakage).



I have a upper that has about 60 K, the carrier and upper have slight wear marks, meaning you can see where they interface, but thats it.



 

IMO, the most likely unintentional failure mode for a carrier would be the gas rings wearing the ID enough that gas leaks around the rings and causes short stroking or bolt lock up issues due to the lug misalignment. This would require at least several sets of gas rings and would probably be 75k-100k rounds or more before the effect became significant enough to notice or warrant action.





Otherwise, if you were running the rifle significantly over gassed, the rear of the cam groove could get deformed/cracked due to the energy it absorbs from the cam impact (energy that's not absorbed by the recoil spring). Steel has an infinite fatigue life below which the load will never cause failure. So, you would have to be doing something seriously wrong to cause this much stress in the cam groove and the gas key would probably break before the BCG sustained damage.





Or, if you intentionally ran very fine dust/sand in the weapon, something like talcum powder sized but abrasive like sand, this would be along the lines of an industrial dirt wear test. Eventually the carrier would wear down the rails in the upper to a point where it may not align with the RE when in battery and this would prevent lockup or induce cycling problems. Again, this would have to be intentional abuse since we're talking running moon dust in the rifle and not cleaning it, and it would take many many rounds for it to happen. Never heard of this happening in either Sandbox (Iraq or A-stan), so---





No, your BCG will probably outlive you unless you break it on purpose.

 

Earlier this year people were paying stupid $$$ for bcgs......I have no idea why....the supply seems to be back to normal now...

If you have a quality carrier, then you can get a Nickel Boron bolt and be set pretty much for life depending on how much you shoot.

^^This. But as others have said, its a high friction component and will eventually wear out. You'd likely come across many bolt issues well before the carrier has issues itself.

Thanks for the info guys.