Original sentence: The round is colloquially known as the "7.62 Russian," although the "R" is actually arbitrary and the term "7.62 Russian" evolved at a later time when the round was exported to America
Edited sentence: The round is colloquially known as the "7.62 Russian," although the "R" actually stands for "rimmed" in C.cartridge nomenclature and the term "7.62 Russian" evolved at a later time when the round was exported to America