Christ, call it the 'SA80' in my regiment and you'd get a dry slap. It's the 'five-five-six'. SA80 (Small Arms for the 1980's) was the name if the MoD minimum spec when the project went out to manufacturers for tender and has never been the name of the actual weapon.
People still come out with that crap about the UK dropping the the .762 because the .556 is more likely to injure than kill, and thus is a greater drain on enemy resources. Bull. It's Simpky a more appropriate round for an assault rifle, and just happened to have been the standard of our NATO allies since the 60's, so there were logistical and cost advantages as well.
You wouldn't like to move your decimal points one space to the right would you?