They are still both 9mm cartridges, just not the same. 9.01 vs 9.27. I have never agreed with cartridge naming conventions. Most do it to separate themselves from the rest of the cartridges that are out. Neither the 460 Rowland or the 460 S&W are .460, they are both .452 just like any other 45 cartridge.A 44cal bullet is anywhere between .429 and .431 and yet still not .440! Both 9mak and 357sig (noted it's not actually .357) are still labeled as 9mm. If the 357sig was .357 it could be labeled as a 38cal. Take note the 38spl and the 357mag are both used in the 357mag revolvers.