I made a drawer instead of a rack. It goes on the top shelf of my safe.
I figured out about the best spacing for my barrels with scopes, since all could potentially wear one. Then I used my router to put a channel for the barrel to rest in and a slot all the way through for the lug. There is room here for six 10" barrels and four 10" to 14" barrels. I used good quality heavy duty drawer glides which provide full extension.
The rise at the back of the frame is so I don't have to fasten it to the safe. It just sits on the top shelf and the rise rests against the roof, preventing it from tilting when all the way out. The drawer and the sides are 3/4" MDF and the rail across the back is oak.
I spray painted black the parts that would be exposed and then covered the drawer with black felt.
Here is what it looks like in the safe.
As mentioned, the drawer extends all the way out but I only pulled it out part way for the picture.
Curtis