I’m trying to figure out what interference is preventing the upper and lower coming together.
The BCG doesn’t add any physical obstruction to the upper - it’s in battery or else you wouldn’t get that far closing it ….
The only point of restance is when the rear of the carrier comes into contact with the face of the buffer, but the buffer should just be nudged back enough , under spring tension, so that the upper and lower come together properly….
From your 4th picture, it looks as though the buffer isn’t moving back when the carrier is pushing against it.
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This is the point on mine where the back of the carrier starts to push back on the face of the buffer, is your buffer binding on the rim of the tube as it moves back ?
In your first pic, to the left of the retaining pin, it looks like a swath of metal is missing from the edge of the tube
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