A few things:
1) A new extractor spring.
2) A new magazine follower and spring.
3) A heavier buffer.
4) A new disconnect spring.
5) New feed geometry
And according to the reports, the 'moderator' was never intended to fix any reliability problems, it was in fact the source of several problems.
Oh, and by the way, most civilian ARs are under-gassed. Point one straight down and fire it, most will not lock back, nor (I suspect) will most work properly in arctic temperatures.
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