u/Flat_Anybody_2983

Hi all — new to building ARs and trying to keep this simple for my first build. I already have a complete lower receiver (everything except the buffer) and I'm planning to use a PSA upper( picture below). I'd like to just buy a buffer/ buffer spring and a compatible bolt carrier group so 1 can finish the lower and drop the complete upper on also would like to add a super safety( picture below)

1. Any recommendations for a reliable BCG and buffer/ spring to pair with a PSA upper (nothing custom or exotic - just dependable, mil-spec or equivalent parts)?

2. Anything obvious I'm overlooking as a first-time builder such as fit issues, or simple assembly tips)?

Thanks - trying to keep this straightforward and safe.