You have extractor problems that are causing a mess with all the shaved brass, and if you look at the shoulder of the chamber with all the brass build up there, not way in hell that a live round is going to head space correctly.




So pull the extractor, break out a jewlers file, and remove any burs that the find on the ends of the extractor claw end edges/

Next, on the rim releif channel of the extractor below the claw, remove the end of channel burs that are not allowing the rim to slip cleaning on the channel.

Simply, when bolt goes to unlock, the spent case is still pressure welded to the chamber walls, so this means that the entire bolt and extractor are slipping on the spent case rim, until the bolt lugs do clear the barrel extenion lugs, and the bolt/extractor can pull straight back to pull the car out of the chamber.  So it during this rotation of the bolt on the fixed case rim, that is doing all the shaving of the brass.

So if end of claw edges are too sharp, going to shave brass on the rototaion. Note leave the grabbing claw sharp and just deal with the ends of claw edges/burs where they can bite in if sharp.


If end of relief channel on the extractor has burs, going to shave the hell out of the rim on the rotation.


Little cold bluing in the end, and all is right with the world.


As for barrel feed ramps, too dirty to tell, but you want to make sure that the Inside end of the feed ramps at the U and side sections do not have burs that are scrapping the case on feed as well.  Hence could be burs at the ejector bolt face channel that are causing the spent case scrapping on rotation as well.


Once you get the rig cleaned up and the chamber scrubbed with CLP and a chamber brush, post another photo of it, as well as the face of the bolt as well.  

The last area to check once the extractor is cleaned up, is maybe a bur ledge at the extractor on the bolt face that is scrapping the brass, as well as making sure that the rim releif channel with the extractor mounted, is not too low against the bolt face, trapping the spent case rim in as it trying to rotate on the rim.  Hence you should be able to hook at spent case on the extractor, push the ejector in so the back side of the spent case is flush against the bolt face with the case and rotate the case on the bolt face/in the extractor rim relief channel.

Pull the extractor and show me your clean up on it (claw and rim relief channel), the face of the bolt without extractors so I can see edge of bolt face at the extractor slot to make sure there is not bur there, and how the extractor rim relief channel lines up to the bolt face.


Hence extractor is still shaving the case rim on the bolt turn to hell, and we still need to solve that problem so the case rim is not being shaved to hell.  

In some cases, it not only the edges of claw that need to be removed of  tip edge burs, but may need to relieve angle edge the side between the claw tips to relief channel,  so they glide against the case rim on the turn.  Hence cross pin channel in the extractor may be enough none trammed, that it has the extractor slightly canted against the bolt face and why the extractor still shaving on the bolt turn.

As for feed ramps, it's the Inner edge at the U section that should be  de-bured/polished up to remove any edge burs, while the rest of the ramp, light polishing if rough, will just allow the round to feed more smoothly instead.

Also, need to talk about cleaning solvents you are sing, what lube you are using to lube the upper receiver bearing area's, and even the loads, since for the two and few shots, that's a lot of fouling in the chamber that is not brass flakes as well.
Hence 300blk in sub sonic with suppressor is going to have a lot of blow back, but with the correct powder and use of CLP to lube the upper, should not be leaving that thick of a fouling clumps in the chamber, even on a short barrel pistol.