I first thought maybe WRF too but with it having the same dimensions as the WMR except length I’d expect it to result in that same bulging. Second look at the fired case and I’m seeing where it looks to have actually been past the chamber when fired. That’s a no no. How about taking another casting only this time try and grab some of the rifling? Also give us some dimensions to work with so we can help look things up. Lastly how about a picture of the base of the fired case just for general SOP?