I recently purchased an upper at a gunshow that was listed as a "Bushmaster" upper.  I was wondering if there is any way I can difinitively determine if it is in fact a Bushmaster upper?

I began to wonder when I went to attach the new upper to my Bushmaster lower.  When I tried to push the rear pin in it went through the lug on the upper just fine, but then didn't want to come through the left side of the lower receiver.  I had to push it real hard to get it to go through.  When I put my original "shorty" upper back onto the lower the pins just go "pop", right through with almost no effort.  

The second thing that has made me wonder is the finish on the upper.  When mated with my Bushmaster lower, the upper appears very black where the lower appears almost grey in comparison.  

Lastly, the 20" barrel tapers to a smaller diameter in front of the front sight to the end where a three port, "birdcage" comp is mounted.  Did bushmaster make government contour 20" barrels?

Hope someone out there can help me out.

Thanks in advance.

1911guy.

And I've never seen any marks on a Bushy upper receiver, only the barrel.
Thanks.....Chad

I have a Bushmaster upper mounted on an old Colt lower.  The Colt is very gray while the new Bushmaster is midnight black.  If I remember correctly, many new Colts also have much darker finishes than their predacessors.  I don't know if this is an industry trend or a unique case.