Your frustration is understood.Before you proceed any farther inspect your bolt carrier key for gas leakage.The two Allen screws that hold the carrier key to the top of the bolt carrier are supposed to be staked.Check to see if they are,get a proper fitting Allen wrench and check for tightness.A loose key will cause bullets to tip and keyhole.I have seen screws that appeared tight that left a paper thin gap.This causes the exact problem you are experienqcing.Also check and make sure your bolt carrier key is sliding over the gas tube and not dragging on the side .This mis alignment of the tube can also cause problems,while not common when done at the factory assembly it is possible an assembler could be a little too aggressive with the barrel wrench causing the tube to shift.You can check this by removing the bolt from the bolt carrier turning the upper over and gently sliding the carrier forward.If properly aligned it should make little or no contact with the tube and slide over it freely.

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SWCA#2288
SWHF#407