A Remington 591, in 5mm Rem Mag, may have been the 1st rifle I ever bought and I kept it until Remington announced they were discontinuing ammo for it. Another error I made, not keeping a box or a single round but at 19, doubt I knew what a cartridge collector was.
This was a very hot little bullet, available only in hollow point and it literally destroyed whatever it hit, not a game gun. The .22 Win Mag was available in solids and there was greater variance in centerfire .22’s. The ammo was quite a bit higher cost than other rimfires, though I don’t recall the price now. Sales were very slow for guns and ammo I believe. In my town, our Western Auto was the #1 shooters store and they brought in 1ea of the 591 and 592, along with a case of ammo. After I bought the 591 the 592 remained for several years and I was the only person buying the ammo. They never replaced the rifle or ammo inventory.
I think Ray is correct, American’s were not familiar with metrics nor do I think there was the niche for the cartridge that Remington believed. It was strictly a varmit round as offerred and there were well established, better cartridges already in place. It may have been great for shooting ground hogs on the prairie but it was not an Eastern squirrel round and its lack of versatility killed it, IMO. The cost of the ammo did not help either, at least to me.
That’s really a nice gift Remchester. Bet the market is not awash with those either!