The round is going above the chamber, and pushing the bullet into the case. The bolt also runs over the top of the case and crushes it. I didn't have my phone at the range but this pic below gives you an idea of what's happening.

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Recently changed the barrel on this upper. Ran without issue before the swap, only parts changed were the bolt and barrel. WOA barrel and BCM upper. This has happened with three different branded mags that have functioned fine prior. This also happened with three different types of ammo, black hills, federal and AAC. The bolt catch has kept the bcg open every time it is ran empty. Non-adjustable gas block, dimpled barrel. Rifle is mostly ran suppressed, but did function the same unsupressed. Ejection at about 2 o'clock. The failure only happens once every 60 rounds or so.

Below are the feedramps. The reciever's cuts step down into the barrels cuts slightly so there is no lip to get caught on.

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Here I circled the area that the round is being pushed up into inside the extension

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What issue am I correcting here? Wouldn't think feed ramps are causing it since there's no lip to catch on. Being the only variable was the barrel my head is telling me it's likely gas and short stroking once every few mags. That seems weird to me though because it does lock open every time it runs a mag empty and it ran the same without the can. Since the gas block is non adjustable, should I try tossing a Carbine buffer in since it currently has an H1? Or maybe it's overgassed and outrunning the mag and I should try an H2?

To me it looks like the bolt is catching the round coming from the mag in the middle somewhere, not at the rear? If so, this is a problem I see with either weak mag springs or, more likely considering your barrel change, a bolt/carrier/buffer that are too light weight-wise for the barrel/gas system. In short, the bolt is coming back forward too early, not giving time for the magazine to get that next round fully up against the feed lips. Make sense?

Heavier buffer. Heavier bolt, possibly a different spring though I prefer to change the buffer first and see. H2 would be where I start.

This is correct. Ordered an H2. Going to try swapping the H1 for a carbine today just to see if it still locks open, and if it does then I'm pretty confident that it just needs a heavier buffer. You would think that stepping down the buffer weight on a under-gassed rifle would prevent it from locking.

The new barrel is the same length and gas system as the last.

I ran about a box worth of mixed aac, black hills and winchester loaded one round at a time with the carbine buffer. Locked back every time. Guessing it must be over-gassed then. Will run about 100 rounds through it when the H2 buffer gets here and reply back whether or not it fixed the issue. Assuming it will.

It is your feed ramps.  Your new variables are bolt and barrel right ? Almost every time I get a new 300 aac barrel exact same issue.  I don't understand why they don't cut the Ramps right from the factory.  Your round are hitting the barrel Ramps that are cut too high and hitting the barrel extension top of chamber.  I have same issue but my old barrel will feed a potato into the hole if you wanted. Please let me know when you find a solution I want to lightly sand mine down but I'm afraid of getting too deep because the round will then hit the bottom of the chamber barrel extension etc . Don't ask me how I know this lol

Under gassed and over gassed have similar looking failures.

If it’s locking back on the empty mag it definitely isn’t under gassed.

The BCG is bouncing forward faster than the mag can feed the next round, catching it in the middle of the case as you described.

Just following up.

Ran around 100 rounds of mixed AAC, BH, and wolf gold with the H2 installed today using the same mags as before. Mostly 77 grain stuff. No issues. Locked open every time.

Assuming carrier speed was an issue, but in any case the H2 seems to have fixed it.