It looks like I spoke too soon. I just noticed that the 2008 solicitation for the .300 WM PIP was sole sourced to Black Hills Ammunition. The notice was buried in the Statement of Work.
I also found a 2006 NSWC-Crane solicitation for A191 that had been sole-sourced to Black Hills, so it appears that both Black Hills and Federal have produced the older load. I continue to believe that Federal had the lion’s share of A191 contracts over the years.
The current solicitation for Mk 248 Mod 1 appears to be an open competition. I would still be surprised if it was awarded to anyone other than Black Hills or Federal.