What are the symptoms of an overgassed AR?

Is this even a problem if the rifles are reliable?  One of my midlengths ejects XM193 in a nice little pile in the "overgassed" zone, Wolf steel in the "perfect gas" zone, and Remington green box all over the place.  

But, in a couple thousand rounds no stoppages.

That chart is only a guide, it's not always true. I have a 308 with an adjustable gas block and it ejects around 1:00-2:00 but if I adjust the gas down any more it won't lock the bolt back

Charts like that are great at putting emphasis on the wrong thing.  Bolt overrides are the primary symptom of an over-gassed AR.  Basically the bolt carrier is outrunning the magazine follower and you'll get click on an empty chamber, but with rounds still in the magazine, or if the bolt is slightly slower,  but still overgassed, it can also manifest as a failure to eject.  Undergassing can also exhibit these same symptoms.  The way to check is to load a single round at a time into the magazine.  If the bolt locks back on the empty mag after the round is fired, you're over-gassed.  If not, you're undergassed.  Extractor and ejector tension can also play a role here, but in my experience it's more common that it's a gas problem.  

If your rifle is feeding and functioning with the ammo and magazines you want to use, leave it alone.  More problems are introduced by folks changing out springs, buffers, carriers, and adjustable gas blocks because they don't know what they're doing, how to properly diagnose and cure the symptoms their rifle is exhibiting; or, their buddy just said it was a good idea so they dropped the part in.

Is over-gassing a problem? I would say it is. Increased recoil, increased gas to the face, increased wear... The only reason to have the gas port larger than mil-spec or equivalent is to use under powered ammo.

If the bolt locks back on an empty mag, then the rifle is running as it should.

Not this again.  This pretty little picture is not necessarily accurate because the ejection pattern really doesn't mean anything. This topic has been tested and covered over and over here.  

I was thinking the same thing....



 

I think there are different definitions of "over-gassed". The rifle can function as it's supposed to and still be considered over-gassed. Ideally you want the bolt to lock back on the last round with the lowest powered ammo you'll be shooting to extend bolt/carrier/spring/extractor life.

The definition gets blurred if you want more reliability in situations when outside and inside accumulated dirt/carbon can slow the operation of the BCG. Oil helps here of course.

What you're using the weapon for is the question that could better identify if it's over-gassed IMO.

I mean that in terms of diagnosing the malfunction.

Maybe it would be better if you tell us what is wrong with your rifle, so we can help you diagnose the symptoms..

Instead of giving us the diagnosis and asking about what could be the symptoms.. .