The AR's in 308 have two completely different systems.

The first is a DPMS/Stoner, and the second is an Armilte system.
Hence you have to make dam sure that the barrel (chamber) that you have in  play, matches the bolt in play, or the head space is going to be off.

Also, you can not use a Armalite narrow hammer slot carrier with a wide style DPMS/Stoner hammer.

Next is a great deal of 308  barrels come chamber tight as well (side wall dimensions), so you have to not only chamber brush clean them each time you clean (even before you shoot them), but remember to clean and lube with the correct solvents as well.

Simply, after checking Anderson site, It does not tell me if the barrel was chambered DPMS/stoner, or Armlite, and would not be suprised if not only the head space if off for the bolt in play, but  chamber side walls may be too side wall tight as well for an auto loading rifle.  

With luck, the head space is fine, and your smith may just have to take a chamber reamer by hand to clean up the chamber instead.

Once the above is taken out of play, then you can start to determine if the rifle is over functioning, or have a gas leak instead.

This would be a fun one to have in my hands at an armorer course, as it would allow several inspections and discussions as to possible causes and how to fix it.

There are many reasons that a rifle may be failing to extract.  Here are a few possibilities:

When the empty casing is left in the chamber when the bolt carrier assembly goes to the rear, it is a fail to extract.  So when you have a fail to extract and the empty casing is left in the chamber, how do you remove it?  Are you able to remove the empty casing by manually cycling the action, or do you have to force the empty casing out by pushing a cleaning rod down the muzzle and forcing it out of the chamber?    

If you can cycle the action manually and remove the empty case, then you have to try and figure out why the extractor didn't pull it out when the bolt carrier assembly went to the rear under gas pressure.  Look at the empty casing for any signs of oil or solvents that may be sweating out of the metal pores, indicating that the chamber needs to be cleaned with a good chamber brush and solvent, then swabbed out with denatured alcohol to remove all solvents/lubes so it is totally dry.  Look at the lip of the case for marks from the extractor, where it might show deformities or where the extractor isn't getting a good hold and slipping off the edge of the casing.  Remove the extractor and look at the lip where it makes contact with the casing, looking for debris or bad machining where it isn't able to get a good hold on the lip of the cartridge.  It could be a badly machined extractor, weak extractor tension, or several things are out of tolerance in a term we call stacking.  Etc

If you have to push a cleaning rod down the muzzle and force the empty casing out, then the question is what is holding the casing in the chamber.  Start with a thorough cleaning of the chamber to make sure there is no debris or fouling.  With a chamber mirror or borescope, look inside the chamber for deformities, scratches, or bad machining that would cause the casing to stick.  Inspect the front of the fired casings that stick, looking for signs of no free-bore, we have seen the several times on .308 barrels.  If you have access to a borescope, look inside the chamber and at the free-bore area, also gauge the rifle for proper headspace.

Look at the lip of the failed to extract casings, inspect the lips for signs where the lip is being ripped off by the extractor.  If the lip of the casing is being ripped off by the extractor, this is a sign that the gun may be unlocking too early.  If the gun is unlocking too early, then consider adding a heavier buffering system from HeavyBuffers.com, or if you have an adjustable gas block then reduce some of the gas.  Etc    

CY6
Greg Sullivan "Sully"
SLR15 Rifles
TheDefensiveEdge.com
(763) 712-0123

I highly doubt it's a problem with the Federal Fusion ammunition, especially since you're having problems with other ammunition.  Did you or the gunsmith you took it to, gauge it for proper headspace?  Did the gunsmith use a borescope to see if it's a problem like a lack of free-bore?  Inspect the empty casings that are failing to eject, looking at the front, sides, lip, and back end.  Are there any marks or dings that would help indicate what may be going on?  Try manually cycling a few different types of ammunition through it, and when you remove these, look at the bullet and end of the casing to see if there are any signs where the casing or bullet may be getting deformed.    

A fail to eject can be similar to causes and remedies of a fail to extract, but could also be different.  Start with a thorough cleaning of the chamber using a chamber brush and good solvent.  Then swab out the chamber with denatured alcohol to make sure all traces of solvent or lubricant are removed, as any solvent/lube left in the pores can sweat out when the chamber gets hot and cause casings to stick or pull out slow, and sometimes even deform casings.  Clean the bolt carrier assembly, and make sure the gas rings have a seal, also check to see that the carrier key (gas key) is tight and properly staked.  Next lubricate the 7 bolt lugs and rails of the bolt carrier so that they are good and wet (glistening like a glazed donut, you can't get them too wet imho) using a good lubricant like Slip2000 "EWL" Extreme Weapons Lube.  Then on the next range session, only load one round into a magazine at a time when firing, to see if the bolt carrier assembly will lock back after the round is ejected.  If it isn't locking back, this could be a sign that the bolt carrier can't go back far enough from parts that are out of spec or tolerance, or it could be lack of gas pressure, gun is cycling out of proper timing, or there is too much friction where things are dragging, etc.  

CY6
Greg Sullivan "Sully"
SLR15 Rifles
TheDefensiveEdge.com
(763) 712-0123

Also looking at this pic, like you said, it does appear that there is a spot on the lower left side of the buffer tube where the bolt carrier may be impacting it.  Is that also a mark on the lower right side. and another mark at about 12:30-1:00 where the carrier (gas key) may be hitting as well?

CY6
Greg Sullivan "Sully"
SLR15 Rifles
TheDefensiveEdge.com
(763) 712-0123

Again, DPMS seems to think that is a good thing for the face of the bolt to retract back past the back edge of the ejection port.


Hence this can cause problems with the spent case tagging the back inside edge of the ejection port inner surface, and causing the spent case to be pivoted back into the action to cause a stove pipe jam ; even if the spent case rim does not slip off the ejector all the way back to the back of stroke.

So the keys here with such going on, you have to make sure that the chamber has been scrubbed clean with a chamber brush and CLP each cleaning.    
Also, since the spent case is going to ride all the way back on the face of the bolt until back stall, then something is needed to keep the spent case on the bolt face, and to pivot off the bolt face as is starting to move back forward instead.  Hence normally, the spent case via extractor sticks to the bolt face until back of stroke stall, and at this point, the ejector can do it thing to  finally push the spent case off the bolt face via extractor.  This is not going to work since the spent case will take the inside edge of the ejection port window that can cause a stove pipe jam, so something like a sharp extractor, and even adding tension to the extractor spring, will allow the spent case to stick a touch and enough to keep the spent case on the bolt face/extractor until the bolt starts moving forward.

Or the easy fix if your mag springs are still strong, is to just pull the buffer bumper, break out some cotton patchs, and pack all the buffer weights to the front so they will not move instead.  By doing this, you delete the dead blow effect of the buffer (which is not needed on a semi auto rifle), which prevents the stall of the B/C on the back of stroke, and now instead of the spent case wanting to pivot off the face of the bolt at the back of stroke, it pivots off the bolt face as the bolt is starting to move forward again.

So the down and dirty, make sure that the chamber is chamber brush cleaned, and you are using the correct solvents to clean and lube the rig (sweets for the barrel bore, and CLP for every thing else.
Pull the buffer bumper, and pack all the spring weight all the way forward so they stay there with you re install the buffer bumper.
With the rig correctly cleaned and upper receiver areas correctly lubed with CLP, load only a single round in the the mag, insert and charge the round while leaving the empty mag still in the well, and shot the single loaded round.   The bolt should lock back (catch in front of the bolt face, not under the carrier alone) and the spent case should be ejected 10' to 15' out of the ejection port in the 2:30 position.
Do this to get me here on that is going on, and then tell me if the ejection path and distance is correct as noted above, as well as if the spent case rim is bent to hell/the sides of the spent case all marred to hell instead.

Sides of the case all marred to hell tells me dirty/rough chamber problem, while bent to hell spent case rim by extractor tell me that the bolt is trying to unlock too soon instead (powder used in the ammo is burning too slow, and causing way too  high of gas port pressure although the over all working pressure of the load may be fine instead.