I purchased a .300 blackout 14.5 inch upper from a well known person. It has a Montana barrel, Bushmaster receiver and BCG. I started with hand loads but they would not cycle. It will fire but then short stroke. I purchased the recommended buffer and spring that AAC describe along with factory ammo. It still does not cycle. Suppressed or unsuppressed. It is a DI setup. Any ideas as what to try next? I thought maybe the gas port on the barrel is not aligned or the hole is incorrect diameter. Does anyone have an educated idea?
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