Could there have been a small amount of a different powder left in the hopper from a previous reloading session? The bottom, non-translucent part of it could easily hide a decent amount of a fast burning pistol powder if one wasn't being careful. An accidental duplex load of pistol and rifle powder?
Dump in CFE 223 without properly checking for a small amount of remaining powder, drop a measured 29 grains and seat a bullet. All rounds are normal, sans the first one. Said duplex load gets shot on the 2nd round and chaos ensues.
To me, that would explain why the first shot was fine and why all pulled loads showed what appears to be 29 grains of CFE 223.
The bottom of a powder hopper could easily hide 10 grains of Bullseye, etc.
