It appears to be the old BP 10X47R chambering. I'll have Lee do a chamber cast Monday. C&H has the dies, and Huntington's has 9.5X47R brass, an easy one pass through the sizer proposition. I ordered some 180 gr and some 220 gr cast bullets. They are for a 40 S&W and are the correct .401 diameter. With luck I'll be smoking up all three barrels soon.