Here is a pretty good breakdown on dimensions: https://www.stockysstocks.com/contours/
However, i'm pretty sure you could tell McMillan that it is a "Heavy Magnum Contour" and they'll know what that is.
Shank Size will be small, yes.
Length installed in the action - I have no idea what he means. Maybe he means Length of Pull?
If he means length of pull, here is a good article describing what that is:
http://blog.cheaperthandirt.com/length-pull-matter/
Bookmarks