AR std Service Rifle sight radius...?

[Canuck-IL]

I'm googled out ... can someone tell me the sight radius on a std AR (20" barrel)? It must be common knowledge as all the manufacturers of Service Rifle compliant uppers don't seem to mention it.

TIA
/Bryan

 

[mp510]

It's 20" from the front of the rear sight to the rear of the front sight.

 

[Canuck-IL]

Thanks much!
/B