The case is a necked up .223 and from what I understand volume its some 30gr water. Can somebody run some quick load data for some 155amax bulets seated to mag length? Many powder selection is varget, blc2, 1200r (alliant), 300mp (alliant).
Not sure if the above helps you as the 7.62x40 was really intended for bullets less than 150 grains....If you got 2050 FPS out of that bullet from that case, it'd be screaming....