Acceptable quality and finish, except... - Nikon P-Series Mount 835,1 in

I have used Nikon mounts exclusively lately but this pair just might change my mind and lead me toward other brands.
The rings fit the scope perfectly without bind, but the mounts will not slide onto a pic rail correctly.
Thinking that maybe I had drawn an out of spec upper, I tried another, and another. Neither of the rings in this set will slide onto the pic rails. If this had been my 'first rodeo', I might think I was making a silly mistake and missed something obvious.
I'm not very proud of buying stuff like this that needs modification right out of the package to be used, thus my low rating.