I Think Ruger actually made the earlier models with .308 and changed later to .310.
7.62X39 is actually .792 mm (.312) not .308 and somewhere around 120-130 grains.. However, It is
More common to see this round loaded with .310 metal Jackets, Hornady makes a couple bullets for this
at .310… With the designation of 7.62x39. All this info should be in your book.