The Barrett M82A1′s rail has a built in 20MOA can’t built in. This was known.
The Nikon M223 Mount has a 20MOA cant built in. This was NOT known. (It’s not on the packaging anywhere, but it is on the website)
As it turns out, 40MOA of incline doesn’t work. Unless you want to be 5 feet high at 500 yards with the scope adjusted to it’s full range of movement… yeah… that’s not good.