Yeah, chamber cast is best but I'm still perplexed why a 1/2 increment length was stamped like 74 1/2. There must have been some confusion in the submission of the intended cartridge. You see the 1/2 on some chamberings like:

6.5X48 1/2 R
6.5X58 1/2 R
8.15x46 1/2 R
8X48 1/2 R S&S
8x58 1/2 R S&S
8x74 1/2
9X58 1/2 R S&S
9.3X74 1/2 R

And I'm sure there are several others.

Kind Regards,