cousin's mag being dumb

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hey guys. i went to fill my cousin's mag. as i was filling it, i hit about 500 psi and the thing goes full auto. i might be thinking it's the shim or carrier. i could fix it, but i don't have the time or patience. lmk if you guys have any solutions.
it's and x-valve w/ ult and level 10

[afultz075]

Probably too many shims in the ULT.

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that's exactly what i thought. i just wanted some input before i go screw more stuff up. thanks