Via Theo Spark.
I’ll let Esli explain what the Muzzle Reference System is, and how it works.
It’s interesting in the age of hypervelocity kinetic penetrators and HEAT rounds, the Brits chose to go with a rifled 120mm main gun for their Challenger II Main Battle Tank. High rotational speeds are not desirable for either type of round. I’m curious what the thought process was behind that decision.