Polish the feed ramps every time you get one from BCA lol (they make good ones, but they're also fast, meaning things slide past QA)... just use a dremel tool and a steel wire brush tool. If you HAVE access to a sandblaster you could microslick the ramps as well... not only does that make almost anything and everything feed like a dream, it makes it erosion resistant so steel shells are no longer a problem.
(Asked the husband) New magazines. Those ride low... he says they don't push the tip of the 350 round fully over the lip of the ramp, and thus the BCG slams the bullet into the sharp edge of the ramp... where it wedges in place. You need a magazine for the 350 that angles the front of the round upwards, and he said CMMG for preference.
As a side note I'd like to mention even his AR he's made Bolt action, he isn't much for owning Semi Auto rifles after leaving the service, so while yeah. He works on them, but not many people bring ARs into a Gunsmith shop. Everyone works on their own, soooo, grain of salt since he isn't looking at it.