When I built my SBR I did it with an M4 upper because I wasn't sure if I wanted to use my carry handle or put a red dot on it. After shooting the carbine in both configurations I decided I like the iron sight combo better. One problem I had with the carry handle was the knobs. They are huge. I could have replaced them with nuts but then that would somewhat defeat the purpose. Another thing that bothered me was the fact that my fat middle finger knuckle wouldn't fit through the handle.
It was then that I decided I would switch to an A2 upper. Thanks to this site I was able to aquire beaucoup information about the A2 platform. One assumption I made that was wrong was that I could use the sight parts from my carry handle on the A2 upper. Of course I was wrong.
Now that I have it together I am very happy with it. I have always liked the look of the A1/A2, I guess it is because of my age, having been a child during the Viet Nam war. Something about Stoner's lines are just right. One benefit of the A2 upper is that it weighs 5 onces less than an M4 upper with a carry handle.
Untitled by
John, on Flickr
Untitled by
John, on Flickr
Untitled by
John, on Flickr