If ruger would use some common sense in their proprietary cartridges, such as stretching standard ones like SW does, I might buy, but they don't.
It isn't proprietary.
It's a SAAMI-registered cartridge, which means anyone
can manufacture the firearms and ammunition.
And, if we never had anyone attempting something other than stretching existing cartridges, there would be no .500 Special, .40 S&W, etc...
Plus, stretching the cartridge doesn't, necessarily, mean anything at all.
.44 Mag has a longer case length than .44 Special, but they share the same overall length. That means the extra case length is completely useless (and essentially only cosmetic), from a performance standpoint. You can load .44 Special just as hot as .44 Mag.