Anyone else run into this?  I bought a Dirty Bird "M16A1" stripped upper from AR15 Discounts last May, and got around to assembling it yesterday.  It's a nice looking piece, good finish and appeared to be in spec, but the danged thing didn't fit in my clamshell type vice blocks I've been using for going on 20 years.  I've had, trust me, a bunch of every kind of AR15 style upper known to man in that thing, without issue, so I was really surprised this problem came up.  There is a height difference between the spec the blocks were molded to fit and this Dirty Bird specimen's "vertical" dimension.  Specifically, from the top of the carrying handle to the bottom of the receiver, it's just a wee bit too tall.  The work-around I came up with was to remove the clamshell's hinge pin and more or less press fit the left and right sides onto the receiver vertically rather than like a book closing.  It worked well enough, but getting the clamshell halves off the upper took some judicious mallet work.  The end product looks ok, but I doubt I'll buy another one.

Can you post some pics?

Read here: https://www.ar15.com/forums/AR-15/Dirty-Bird-A1-uppers-/123-787229/

Sorry, too late for pics. It's all assembled.  Thanks for the links back to earlier discussions.  My guess is the Dirty Bird folks obtained a substantial quantity of those things and won't be offering them again, but given the prevalent attitude of online vendors I seriously doubt they or AR15 Discounts are going to confirm or deny that.  It's worth repeating the receiver I have turned out okay, but the time I need one I'll likely shop elsewhere.

I've built on DBI receivers and like them in general. I tool a look at the posted threads, the AR15discounts listing, and Dirty Bird site. There are a few disparities in the images in the official pics but one thing is clear, these aren't the pirate uppers referred to in previous threads. The finish work is far cleaner for one. Another thing that is unclear... the official pictures show CA Mark's and no marks. One customer photo showed CH marks on AR15discounts.

I don't know what the deal is with these but, if they look right and they function well, I wouldn't be concerned about them. They could be contract uppers for someone. Who knows. Certainly doesn't have to be Colt.