Re: 6.5X50mm (Jap)
An older Sierra manual that I've got still has a 6.5x50 section....I forget which edition but it's from 1990 or so.
The current 7th edition Hornady manual still has 6.5x50 Arisaka data. Page 298.
The 4th edition Hornady manual (circa 1991) has the 6.5x50 on pg.226.
I've got no scanner here at the apartment otherwise I'd throw a copy up here for ya.
Also check the Hodgon data center that Alpo linked. They've got a few loads listed.