Introduced in 1970--a good 11 years after Winchester had releasedthe popular .22 WMR--the modern-looking, bottlenecked 5mm RRM arrivedloaded with potential. Here was a hot, fast, varmint number capable ofpropelling a 38-grain .2045" diameter, hollowpoint bullet to 2,100fps.
It was 150 fps faster than the fastest .22 WMR of the day. With the improved sectional density offered by the 5mm bullet, it was effective out to 150 yards or so on varmints. In fact, in my home state of Arizona, the 5mm RRM was approved for hunting javelina, legally considered a big game animal.
And it was a complete 5mm flop, due in large pa