Need help with semi auto L4A4

[browningautorifle]

A case separation isn't from excessive gas, it's from an oversize chamber. Excessive gas can rip off a rim however, stuck cases will rip off a rim... I doubt the manufacturer is starting with new barrels and just because they parkerize them and make them look new doesn't help. If your chamber is fat it can rupture too. I had lots of case separations over time with machine guns, all excess headspace issues.

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[TactAdv]

......just because they parkerize them and make them look new doesn't help.

Yes. Listen to THIS.

“Parkerizing” is nothing more than phosphoric acid etching of the metal surface. As it is intended to do it causes microscopic pitting of the smooth surface. Among other things, this in effect causes the surface to become rough and porous, obviously no longer smooth much less polished.

Parkerizing a barrel chamber is -ALWAYS- a very bad idea!!!

Fortunately, it is largely reversible and easily fixed by liberal applications of something like FLITZ metal polishing paste, applied by fully coating a rotary mop (I use a cotton shotgun chamber cleaning mop, appropriately sized to the chamber you are working.) and placing the shaft of the mop on an appropriate extension and powering it with a portable hand drill, Dremel tool, etc. Use medium speed and make sure the FLITZ paste never dries out while turning.

Go CAREFULLY.....you can EASILY remove a .001” of metal quickly!! All you want to accomplish is to polish out the microscopic porosity left from the Parkerizing. It does not take much time to do this.

Once you have removed the porosity and restored a smoothed, polished finish you will likely find your case sticking issues are resolved.

You WILL discover you have increased the overall chamber bore dimensionally a very slight amount which SHOULD not be a problem.

Also.....all this being said above....you did not mention whether or not your .308/7.62 barrel is original military (guaranteed chambered correctly originally), or a new-made aftermarket tube.....where no explicit chambering dimensions are necessarily guaranteed. If new-made I sound almost CERTAINLY expect it to have been cut to SAAMI-spec .308Win chamber dimensions, and NOT to military-spec 7.62x51NATO dimensions, which would easily be a problem as you describe if it was SAAMI cut to minimum chamber dimensions which are ALWAYS intended for bolt-action rifles for maximum accuracy.

If you have a new-made tube, and you’ve tried the after-Parkerizing Polish to no avail, locate a COMPETENT person who can re-cut the chamber using a proper 7.62NATO reamer.
-TomH

[SleepyDoc]

Sorry for the delay. Very busy. I appreciate all the help and will try to get back to your help as soon as possible.

As far as I am aware it is all original military. Barrel is marked Enfield. All bolt parts and carrier appear to be Enfield as well. It was originally a converted Mk2 by the UK military to an L4 when they were switching over to 7,62x51. After it was cut upon entry into this country it was rewelded by Historic arms. I do not see any aftermarket parts other than the SA conversion parts. I do not have throat erosion gauges to measure and do not know how to measure the rest of the chamber. I gave it my best to headspace the gun with the gauges I have and it seems OK, but I'm sure there are other variables to check as well. Closes completely on 308 go and no go, but will not close on 7.62x51 max gauge.
I assume the gas ports have been reamed per Len's MO and the gun will not work on setting 2, but will on setting 3. This corroborates that thought as well.
When I sent the gun back to HA for a look over I think he polished the chamber, but I cannot recall. I do see the rings on the shoulder of the cases which is odd, but I can't imagine this is causing enough sticking. Len had said that he had it running like a sewing machine on Radway Green ammunition (can't find any), but everything else I have tried thus far has not worked. I have not tried steel cased (don't want to), still need to try PRVI x51 and many other European surplus rounds to see if they will work. Too bad everything is out of stock and costs an arm and a leg. Lake city 2020 and other US surplus from the 60s and 70s hasn't worked, nor have my reloads. All rupture.
I have been waiting for SARCO to get their barrels back in and I will buy one of their parts kits with it to get extra parts to try.
As far as quick things to check that will not cause much damage and then working up to potentially destroying parts to fix the issue, what are my first options to check out what could be the problem? I could try polishing the chamber, but if anyone has a way to measure the chamber first to see if there is in fact an issue first, I would greatly appreciate hearing how that is done. The cerrosafe I have expands too much and I was told it is not a good surrogate.
Any input on first steps for checking or fixes would be appreciated. I'm leaning toward trying to polish the chamber first, but I would like to hear everyone's opinion on what would mess up the gun least first. Am I understanding correctly that the South African barrels will not work in the L4? Those are the only ones I can find readily available. Everything else will be aftermarket SARCO barrel.

What solution are you seeking? - A working firearm that will not have case ruptures.

Thank you all again for help in this matter. I have been hitting my head against a wall trying to figure out what to do.