Marrakai,

Thanks for posting. I had read a similar description of the I & S bore diamaetrs on rifles.

I have a BSW DR in 8x57 that mikes at 0.323" for the first couple of CM and then tapers fairly quickly to 0.318". The previous owner said he shot S bullets (0.323") however, because this is a double rifle, I only shoot 0.318" bullets. If this was a bolt rifle, I would use the more common and more available 0.323" bullets.