That's my scope,and I don't remeber making that measured pic- but that doesn't mean I didn't 
The measurements seem about right though.
Anyway, if you want the best way to get the measurements, I would suggest scaling a photo of the real prop up to the same size as the denix rifle. That is what I did.
I also threaded the end pieces onto a ready made tube stock. I remember that it was smaller than 5/8 so 1/2" sounds about right. I had a real hard time getting them to screw onto the tube absolutely straight, but once the gun was all put together, it was hard to tell.
-cris
