After whining about the lack of 310 items and high prices, I just received an interesting set. They are marked "65 X 257". First pair made for a wildcat caliber I've ever seen, I assume it was a 6.5 mm on a 257 Roberts case. It came with a #8 priming chamber which means absolutely nothing! The recess for the shell head measures .465. Apparently, this cartridge was created to use in the returning Japanese 6.5x50 rifles GI's were bringing back. I've heard of rifles being found marked as 6.5 x 57. Anyway, I thought it was interesting! Now to find the dies!