I think Der Ami is correct. If rimmed, it is the 6.5x53R Mannlicher, also listed as Dutch or Romanian Mannlicher. Loading data for those or for the 6.5x54 Mannlicher-Schoenauer or for the 6.5 mm Italian will give reasonable starting points. A few years back, Sellier & Bellot loaded this cartridge & they were imported here. Those have Boxer primers. I have a set of case forming & trim dies, for making cases from .303 British. To me, it is a lot of work for what you get. If you can find the S&B ammo, and if your time is worth anything, that is thre way to go.
Also, Phil Sharpe's Complete Guide to Handloading covers the cartridge. Sharpe's book is available as a free download on the net.