Could be wrong, but some of the frames are metal and some are mostly polymer??? I think the broken frame in that picture you're referring to is metal. Why would it crack?? I can't really say. Could have been a defect in that particular frame or it could have been thrown against a wall. Not impying that it was. I had one with your type of frame and they are built to last. I only got rid of mine 'cause I didn't like the rail that you could not remove. Got a Ruger MkIII 22/45 to replace it. Enjoy yours. It's a fine pistol.