My brother purchased a complete upper, unfortunately it was a 16" barrel instead of 14.5" (his bad - ordered wrong part number). He called Bushmaster who told him to ship it back and they would swap it out saying it would take two to three weeks. Cool. He was given an RMA# and FedEx'd the upper (received by Bushmaster on 08/16). Over a month later he hadn't received the replacement, so he called (on 09/20) and was told it would be another two to three weeks. A little over three weeks goes by and nothing. He sent an email (on 10/16) asking for an update and never received a response. On 10/29 he called again and was told they would call him back on Monday. He never got a call. He called again on 11/02 and was told it would be another week. Really? I have the RMA if Bushmaster is interested in resolving this.
ETA - Proactively sent BM the RMA so they would know the above it straight up.
Update! A response to the email he sent to customer service almost a month ago was received: it said to call their 800 number...
Update #2: After yet another phone call and requesting to talk to management, the upper was received three days later.
Bushmaster's ETA on the upper: 14 - 21 days.
Actual time: 96 days and ticking...