Magnum Research.
Made a notable object as it has been in many movies including The Matrix.
Originally designed as a modular platform that could be swapped with various magazine/barrel/slide combos on the same frame.
If it's good enough for the Israeli's...
Some shooter with more money than brains keeps leaving a bunch of .50AE brass at my local range. Yeah, I pick it up. Nope, nothing to shoot it out of yet.