Just to clarify, it's really I, not J, the J was a misreading of the German fraktur font I for Infantrie, it stuck in a lot of English language literature.
You have 4 versions of the round, I, IR, IS and ISR. I (and the rimmed version IR) were introduced in 1888 as the M88 infantry round with a 318 diameter. In 1906 they introduced the IS cartridge, using the same brass but with a heavier 323 spitzer round (guess who copies that as 30-06 to replace the just introduced 30-03).