I'm new on this site but, have been lurking for a while.
I ordered one .450 upper on March 30. I called a few times about the status. Bushmaster changed it's system some time between then and now and so on Tuesday this week I received TWO .450 upper receivers. I sent one back that night and it arrives back at Bushmaster today so, one of you should have one coming out that was in Maryland.
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BTW, the one I kept arrived via UPS, the one I sent back came via FEDEX. The one I kept has the quad rail gas block which I did not order but, am happy to have.