I door-gunned on Hueys for awhile in Nam. We always kept the A1 as a back-up to the M-60.
Some door gunners kept M-16s (one had three banana mags made into a single mag with 100 mph tape), others had AKs with the buttstock sawed off.
Went into an LZ & the DG’s bbl assembly flew off into the grass; barrel latch open. No problem, grabbed his AK pistol & continued to lay down fire.