Flat spot on case mouth.

[kmon]

Since you have an adjustable gas system, I would give it a little more gas. Less buffer spring like mentioned above could do it as well. An over gassed system usually ejects forward of 90 degrees of the ejection port which is what I am currently getting with mine, and will be replacing the buffer spring with a stronger one or replacing the gas block with an adjustable one.

I am sure this has been posted many times but

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