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And also tried the BCG from working rifle, but still jam every several rounds.
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If initial loadings, then make sure that the threaded section of the mag catch is flush with the face of the mag release button, and that the hammer is not catching on the FP, or FA pawn catching on the carrier notches.
Next, might help to pull apart the mags to give then a good CLP cleaning, and make sure when you are loading mags, consider the mag full when the top last loaded round can be push down at least 2/3 of the way being able to load another round.
From there, pull the bolt off the carrier and dry fit the carrier with key alone in the upper receiver. This will tell you if the key is too wind and binding on the upper slot for it, as well if the gas tube is not correctly indexed to the carrier key.
As for Mobil 1, Great oil that I use in the Vet and on my lathes and mills, but regarding the AR platform, CLP is the better lube.