Carrier has to come back away from the barrel extension face before the bolt lugs will unlock from the barrel extension lugs.

So pogo method is use to at least get the carrier back to unlock the bolt, and if the case is stuck well enough, the extractor just rips the rim of the case, leaving the spent case still in the chamber.  As this point you can lower the B/C back down enough to push both take pins to the side to remove the upper from the lower, drop the B/C out, then you now go down the muzzle with a single piece cleaning rod to knock the case free.

And again, if the bolt is locked, no amount of pounding down the bore is going to rotate to unlock  the bolt.

Worse case, and you can not pogo the rifle hard enough with charging handle pull at the same time to get the bolt to unlock (have yet to comes across this myself, since I pogo hard enough to at least rip the case rim off to get the bolt to unlock in the first place), then with upper off the lower, you can use a wedge tool between the front of the carrier and back of barrel extension to walk the carrrier back to get the bolt unlocked that way to begin with.

To add, on a carbine rig, make sure to have stock in the closed postion, or just pull down on the butt stock lever to remove the telescoping stock from the receiver extension to start with.

No, leave the carrier key alone, since you can damage not only it, but the upper receiver gas tube channel.

To short bus it, remove the butt stock from the receiver extension if a carbine rig with telescoping stock,, put a piece of carpet on your reloading bench, and do the Pogo/mortor blows while pulling down on the charging handle.  The inertia of the downward force coming to a quick stop helps the carrier work in your favor, to get the bolt unlocked.  Hence even if you rip the rim off the spent round and the spent case stays in the chamber, at least this gets the bolt unlocked in the first place.  So again, its too easy to Pogo with the charging handle pull to at least get the case rim to shear off, without harming the rifle.

[youtube]https://youtu.be/kzBdyubc0Uk[/youtube]

Or, if you can not pogo to get the carrier back (don't have your big boy panties on), then wedge tool between the bottom for the carrier and front/bottom of the barrel extension (since both are harden metals) will work to get the carrier to come back, cam the bolt over to unlock it from the lugs to tear the rim off the spent case.  And now with the bolt unlocked, you can use the single piece cleaning rod down the bore to drive the spent case out of the chamber.

Bottom line, until the the carrier comes back to cam over and  unlock the bolt lugs from the barrel extension lugs, any force down the bore against the locked bolt, is not going to unlock the bolt.  At most, all your going to do is shear the bolt lugs of the bolt.

Its not the hard hit, but the the abrupt dowward stop of the rifle, with the carrier still moving downward that really unlocks the Bolt on the stop.

In the case of the video jam, it just a bad feed of a live rund, and your case with a spent round instead, will take a little more mortor force isntead. So for this reason, pull the butt stock off the receiver extension, so you mortor down on the back of the receiver extension alone.

Just remember, if the case is really stuck, we are just trying to get the bolt to unlock, and shear off the case rim to start with.  This will have the B/C back so you can lock it back on the bolt catch, then use the single piece cleaning rod down the muzzle afterwards to clean the spent case chamber, without the bolt locking the spent case in the chamber.

Nice nightmare.


Strip the FS off the barrel, and pull the gas block.

Now upper vise clamp the upper, and using a barrel clamp  wrench on the barrel or band wrench if that is all you have , we need to align the barrel extension feed ramps back to BDC, then correctly tighten the barrel nut up correctly on the mono upper receiver.

Now with the barrel feed ramps correctly indexed again, and the barrel nut tighttened to at last 60ftlbs, should be able to mortar the rifle the last of the way to shear the rim off the spent case and get the bolt to come back, to lock the bolt back on the catch, then send the single piece clearing rod down the barrel to knock the spent case out of the barrel.

Now pull the barrel nut , pull the barrel and clean the chamber, drill out the snapped piece of the barrel extension pin (other piece should fall out when you remove the barrel), and install a new extension pin.  Now drop the barrel back down into the barrel socket, and since the upper barrel socket pin channel has been peened when it snapped the barrel extension pin, your going to have to make sure that the Feed ramps remain on BDC as you tighten the barrel nut to plus 35ftlbs, but do not exceed 80ft lbs to index the barrel nut top spine so the gas tube can cleanly pass through the barrel nut and gas tube channel.

On the gas block with gas tube, temp install it indexed to the center line of gas port, pull the bolt off the B/C so you have just the carrier with key, and dry fit it into the upper to check the alignment of the gas tube to carrier key, and tweak the gas tube as needed.

And who every install the barrel to begin with, needs a swift kick in the nuts!!!!  
Hence barrel nut tightened to at least 35lb, then tighten more to index the barrel nut channel/top spines, should not have have had the barrel twist in the upper when mortaring to start with. So who every tighten the barrel nut when the upper was built, had the barrel nut at less than 35ftlbs to start with.

Broken barrel extension pin is not the end of the world, since it just pressed in, and can be spun back out with a small drill bit.  The new extension pin can be just pressed/lightly hammered back into the channel for it. The pin is just used for inital indexing of the barrel in the barrel socket, and it the barrel nut that should be holding the barrel tight in the upper receiver barrel socket isntead.

As for monolithic upper receiver with the built in hand guard, some are good system, while others not so much.  Hence it all boils down to if the system  will allow the barrel to be locked in place with a high enough specs or not in the first place.

Hence the mega torques to 65ftlbs after you have lapped the threads in with torquing to 65, loosening, torquing to 65, loosening, then final tightening to 65ft lbs.
[youtube]https://youtu.be/sUigxKmbKZ4[/youtube]

Other monolithic barrels use a bolt clamp type style to lock the barrel in place, but not really fond of such, since the cross pin is not really deep enough through a mating slot/pin can peen to prevent the barrel from slipping from lateral torque isntead (bayonet type use).
[youtube]https://youtu.be/uX1CCy4A1iE[/youtube]

Lets not make a mess of this!!!!!

Upper receiver gets clamped in a clam shell vise block with channel insert so you don't crush the side walls of the receiver.

Barrel, I prefer the wood block type clamp T bar wrenches so I not maring the hell out of the barrel finish, but if push came to shove, piece of thicker belt type lever around the barrel, and then a good clamp type wrench like Channel locks to get grip on the barrel to run it with the leather soft jaws between it and the barrel, again so you not marring the finish on the barrel when you go to turn the barrel extension back to the correct index.

At this point, remove the barrel nut, and let the broken barrel extension pin fall out to get it out of the way.  Since you do have some room of the carrier moving backwards in the barrel extension, you may have to work the barrel slighting in and out of the barrel socket if the broken pin is trapped between the barrel extension lip and front of barrel socket surface to allow the sheared pin to drop out.  Hence we need to get the barrel extension lip tight against the front of the barrel socket before we tighten the barrel nut again.

Now you can reinstall the barrel nut, tighten it to 65ft lbs so the barrel is not going to spin again in the upper barrel socket.

At this point, forgo the mortar method and just use a pry tool between the barrel extension face and the face of the carrier to work the carrier all the way back to unlock the bolt lugs from the barrel extension lugs, and to shear the rim off the spent round via the extractor.

Now with the B/C unlocked and removed from the upper receiver, just remove the barrel from the upper receiver, with the spent case with torn off rim still in the barrel chamber.  Single piece cleaning rod down the barrel against the webbing of the spent rim, chamber upwards, you do floor taps to the cleaning rod handle to drive the spent case out of the chamber.

At this point, it time to break out the chamber brush to clean not only the chamber, but the void and lugs of the barrel extension.

Now back on the broken barrel extension pin, mill to center drill out the sheared pin still in the channel, then press a new barrel extension pin back in.

On the upper, take a look at the barrel socket slot for the pin, and if it not too bad, then standard clam shell upper vice block with barrel nut wrench is all that is needed.  If the upper receiver barrel socket slot for the pin is totaled, then still no fear, since you can use a reactor rod to hold the barrel extension indexed correctly to the receiver as you tighten the barrel nut instead.

Really, the only downfall, will be if the barrel nut threads on either the nut or the upper receiver at stripped to hell and need to be replaced instead.

Lastly, since your upper appears to be a monolithic upper, knowing which one is its, will go a long way to add some other tricks as well if down the line you need to mortar again, to keep the barrel from spinning again in the upper receiver socket.
To add here, when you do moly grease for an barrel install, its only the barrel nut side of the barrel extension flange that gets greased.  The barrel extension body, and even the inner flange to socket face, does not get lubed, and in fact lefts in a dry start to maintain as much friction tension to prevent the barrel from rotating in the first place.

Short of the barrel extension pin that needs to be replace, the rest of the parts just need light file/sand paper clean up.

As for the spent case, the round when way over pressure, so would weed out just what happened.
So on that note, give the barrel and chamber a good cleaning, then check the barrel bore for a budge via jig and tight clean wad down the barrel to feel for any loose/budged spots in the bore that may have happened with a obstructed bore (to cook the barrel).

If barrel was not obstructed to cause the over pressure problems, then may have been back at the loading processes, with some faster burning powder that made it way into the round if you are sure that rest of the loads where not going over pressure.

My guess since the gas tube will hold the barrel nut in place even if slightly loose, that the gas block with gas tube was  pulled at some point and maybe even the barrel nut loosened.

Hence barrel extension pin should be almost at the bottom of the upper socket slot,


And when the barrel slipped/rotated in the upper socket, you can tell that the barrel was not fully seated tight against the front of the barrel socket edge.


Also to point out, when barrel is seated fully in the upper barrel socket, back face of barrel extension should be flush with the inside of the front wall of the receiver a well.

Hence in this photo, you can see the back of the receiver extension recessed against the front wall of the receiver.  So don't know if it was a loose barrel nut to start with, or the barrel not fully seated at install instead.


Hence when the barrel slipped in the upper socket, it should have scored the hell out of the barrel extension flange seating surface, and not just chip off the paint coating at the barrel section OD barrel section the upper instead.  Hell, take a good look at the coating inside the receiver barrel section, and it looks like it prevented the barrel extension from fully seating in the barrel socket  against the flat for the barrel extension flange to begin with.


So when coating a upper receiver, it's fine to coat the exterior of the upper, but tape off the inner surfaces so your not building up these bearing area surfaces to cause problems instead.

Just keep in mind that on the barrel extension flange seating area in the upper, need to get the high peen spots back down so the barrel is not cocked against the upper receiver center line when the barrel reinstalled.

You don't need to go as far as machining the entire surface back squared to the upper receiver line, and in fact just making sure that the smaller peen raised area of the seating flange is flush or just below the rest of the plane for the flange instead.

Also, take the time to clean out the coating in the upper barrel socket area so the coating there is not blocking the barrel from seating against the socket flange, or trying to cant the barrel off center line from the OD sides of the barrel extension to socket channel as well.

Hence it really the barrel extension flange seating against the upper barrel socket mating surface should be holding the barrel in line with the upper receiver line, as well as 90% of the tension holding the barrel in place (so it does not rotate as well). If your looking to further lock the  barrel extension to upper receiver barrel socket, there there are some good loctites that can be used.  This allows the barrel to be installed while the loctite is still wet to achieve the center line index by barrel nut and upper barrel socket seating flange, then as the loctite dried, fill in the void area of the OD of the barrel extension to ID barrel socket to hold them in place. The Downside to this kind of NM mod, is that when you go to pull the barrel, heat is required to break the loctite bond, and will not work so much with a coated upper receiver.

To add since I bring up centering the upper barrel socket seating surface for the barrel socket flange, the best way I have found to index the upper receiver before doing this, it to use the upper receiver scope mounting rail.  Too many times I have seen the ID channel of the upper receiver for the B/C not machined true, and if you use the channel, can end up with the barrel extension seating surface cocked isntead.

So since I need to scope to be looking straight down the bore line of the barrel, will tram the upper receiver off the top and side lines of the scope mounting rail, then square the barrel socket mating surfaces to it.  This way, elevation changes to the scope leveled on the receiver, at straight forward, and not having to deal with the scope cocked to the bore line with the needed windage changes that would result in such for different basic distances scope changes.

Seating flange area in the barrel socket for the barrel extension flange only has the lightest of peen high spot around the barrel extension pin area, so just use a file to knock the minor high spots peen areas to the right of the barrel extension pin slot, and to the left of the slot down.  With as limited at the spots your knocking down on the baring area for the barrel extension flange, even if they are slightly lower than the rest of the bearing area, will not cause problems.  So on that point, unless your going for perfection, lathe is  not needed.

The bigger one I see, is the coating inside the receiver areas that will be pushing  on the  sides of the barrel extension, and may not allow the barrel extension flange to seat correctly on the socket bearing areas for the flange isntead.  Hence the area where the coating is cracked when you pulled the barrel isntead.  So if you look into the receiver, and see where where the barrel extension end  at the feed ramps ending up in the receiver, from that point back out and over the flange bearing seating area and up the ID threads for the barrel nut, needs to have the coating removed.  I bring up the upper barrel socket threads, since coating on them will end up with a false torque valve and will  just be a problem with the coating chipping off when the barrel nut is correcty torqued to start with.

So really, light filing to knock down the peen high spots on the upper surface flat for barrel extension flange next to the slot , then break out  acetone with Q-tip to remove the coating on the ID of the receiver and bearing flat for the barrel extension to seat cleanly against the upper barrel socket anodize surfaces, and your ready to reinstall the barrel.

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As for lathe work, really advice against such, since will take some advance mandrel/jig making/lathe set to be able to re-machine the barrel extension flange seating surface in the lathe square with the scope mount rail on the upper receiver.  Hell, before even milling the upper receiver, would chuck the barrel in the lathe between centers, to make sure that the barrel extension and it seating flange is square to the bore line of barrel to start with.

With a standard upper receiver, easy to get a live end in play for front of receiver support once you have the upper trammed in the lathe off the scope mount lines, since you're just machining the end of barrel socket with an insert tool.


But since you need to be able to get into the extended barrel socket to use a boring type tool to square that barrel extension flange mating surface deep inside isntead, then will need a barrel/receiver type spider set up to hold the receiver on the mandrel trammed, for turning like  on the locking lugs on a 700 action instead.


So think this, and instead of the receiver in the jig trammed to center line of bolt channel, we have the mandrel in the jig with the upper receiver on the mandrel trammed to the center line of scope mount instead. this way, the scope and bore line are both on the same center line, once we have the barrel extension squared to the barrel bore center line as well.

Will get a false torque reading with the threads, and even the face of the barrel nut where it going to make down on the barrel extension flange lips if not moly-greased.

Hence the two false torques to 35flbls and loosening, then third torque to 35 to begin with, are all to mate the surfaces in to begin with, then the barrel nut is taken past the third 35ftbls torque value, but not to exceed 80ft lbs, to index barrel nut top spine void/gas tube channel with the upper receiver channel so the gas tube does not rub/bind on the upper receiver gas tube channel.

Also, the moly grease prevents the surfaces from galling/later oxidizing, to make pulling the barrel nut off a later time dam near impossible instead.