for 8x50R Mannlicher the groove diameter is .329, the bullet diameter is .323 but the long heavy bullet expand up to 329 in the barrel when fired. a 329 bullet will be perfect if the chamber allow to load such a cartridge and have a little extra space for the case neck so this can expand. long heavy .323 S diameter roundnose bullets give most time good results, boat tails are hopeless.

rifles for the 8x56R with a .329 spitzer bullet were only rechambered.