The "soup" which Ruger (and other companies) uses to form their products are dependent on alloys which differ significantly from the typical iron castings (or zinc, and other non-ferrous castings) we are accustomed to which are often inferior in strength for purposes such as guns.

Specialized metal castings are actually used a lot more commonly - not just investments- than we often realize. Investment casting just happens to allow more complex forms to be cast and done closer to final shape and size.

Sometimes, the air you 'let in'matters less than the air you 'let out'.