AFAIK, Springfield Armory Inc.'s receivers are cast so they don't fit jedi391's criteria.
Now here is the problem. Forging is fairly cheap once set up and in production. BUT, the forging equipment costs like heck and requires really heavy duty support. It also shakes the bejesus out of the building and the surrounding area. (When S&W cranked up production at the old Roosevelt Avenue plant before WWII, the forging hammers literally shook the Civil War era building to pieces.) Those are the reasons most makers choose not to use forgings.
Casting receivers can be done in a strip mall.
Then forgings require more machine work to clean up than castings. (MIM parts require the least work of all, being ready to go as they come from the mold.)