Here in Montana it's been interesting to watch the popularity of the 7mm Remington Magnum over the decades. When it appeared in the 1960's EVERYBODY had to have one, to the point where a friend of mine who worked his way through college by working at a local sawmill, said they issued every guy a hard-hat and a "Seven Em Em" (which is what most people called them, that or the "big Seven," or even just "THE Seven).
It remained really popular through the 1990's, but lost a little steam to the .300 Winchester Magnum. However, when the .300 WSM appeared a BUNCH of older 7mm RM's showed up on used racks at local gun stores, because the boys had read all the hype about how it matched the .300 Winchester Magnum with less recoil.
That last a few years, but lately .300 WSM's aren't selling like they used to, partly because it's harder to find brass, and many .300 WSM shooters are handloaders. 7mm Remington Magnum shooters can be either factory ammo shooters or handloaders, and there's a lot more easily available 7mm RM brass, and even ammo is still far more abundant.
Lately have been seeing about as many .300 WSM's on used racks as 7mm RM's, which is interesting because the 7mm RM has been around far longer, so there are far more 7mm RM rifles around. I don't think this means .300 WSM fans tend to keep their rifles more, either, as I know quite a few who discovered (thanks to chronographs) that it wouldn't match the .300 Winchester with handloads. They also found it kicked more like a .300 magnum than they were lead to believe.
Many if not most of the used 7mm RM's I see on used racks are pretty old, in particular a lot of tang-safety Ruger 77's. I suspect some of those have just quit shooting very well, due to barrel erosion. Found one at a very low price myself a few years ago and that's what had happened to it.
Sevens may not be as popular here as they were 25-40 years ago, but there are still LOTS of hunters carrying them, especially hunters who don't chase the latest fad. And there have been more fads in the past 25 years.
