I know that in 1998/1999 (correct me if this is not accurate) Ruger made and sold the 10/22 designed rifle in 22WMR but then dropped it from their line. In looking I saw where Magnum Research also manufactured a similar design but also dropped it from their offerings.

Is there something about this round that causes these receiver parts to “break” over time? I read where the 30 grain bullet should never be fired in the old Ruger 10/22WMR rifles. Thanks for educating me on this past gun/round design.

I think its more about popularity than durability. Less people want .22WMR. Its an underrated but kinda overpriced cartridge. Just a guess, though.

As I understand it the shape (length and straight wall) of the cartridge and the varying levels of pressure developed by the varying brands and weights of projectiles makes it a difficult cartridge to develop a reliable semi-auto firearm for. That, combined with the price and lack of target grade ammunition negatively affects the demand of a semi-auto 22WMR.

Not sure what Ruger's business model was 25 years ago but as it is today they like most gun makers don't have a problem dropping a product line if they feel they can make more money utilizing their constrained manufacturing resources towards something else. I can certainly tell you that at our retail level that 22MAG rifles of all types don't come close to selling in numbers that justify their spaces on the display rack.

^^^ This. My personal experience bears that out. I've more than once gotten excited about the LGS having a gun I want on the shelf, only to walk away when I discover it's in .22 Mag. I just don't have any use for it. Anything I can't do with .22LR I have .223 for. If they'd designed the cartridge with the proper dimensions to shoot .22LR out of the same chamber (like .22 Short/Long/LR) it would have undoubtedly sold a lot more guns, but they didn't. As a result, it's condemned itself to a niche market.

Yup. Only 22 mag I own is a Colt SAA clone with both cylinders, 22 and 22 mag. I’ve never even removed the cylinder from the wax paper.

I have a Single-Six convertible. I've shot it some in .22 Mag, just because, but it's not very accurate. It's a tack driver shooting .22LR. Last time I had it out with the magnum cylinder it was actually keyholing with the ammo I was using (some CCI variant, I don't remember which).