They list 7.62X39 as having a .308 bullet diameter - all of the soviet rounds including the 7.62X54R have a diameter of .311. Seems trivial, but to a reloader who is trying to find the right bullet size, it could cause much confusion. Anyone with google and 3 minutes worth of time will find this information, I happen to know it because I deal with this caliber - but others may still be learning.
There are many calibers on that page I know nothing about, but knowing they have such a stupid mistake on the soviet bullet size leads me to question the accuracy of the rest of the data.
It isn't really an error, but it doesn't tel the whole story, either. Back in the days when lightweight .310-.311 bullets were not available, it was common practice to load with .308 diameter bullets in the 7.62x54R and 7.62x39. For the most part, before the importation of SKS rifles in the early 80's the 7.62x39 was a very exotic cartridge! Few people even fired it, let alone loaded it.
I know the Hornady manual, a few editions back recommended .308 bullets for both cartridges, and said the smaller diameter bullets still gave adequate practcial accuracy. lee dies for the 7.62x39 came with both .310 and .308 case mouth expanders, and I think RCBS would ship you a .310 expander if you didn't want the .308 expander that came standard.
I don't know if they still chamber them this way, but the early Mini-30 I had came with a .308 bore, and had a throat big enough to chamber .310-311 bullets. Didn't do wonders for accuracy, but could be fired with either diameter bullet.