In 1943-44, Franford Arsenal did a lot of experiments with Steel cases in .30 cal (Drawing processes, Loading, Protective plating etc) The Problems in the field and at production were such that eventually the Experiment was terminated, and all the cases were converted to “Drill” cartridges, by various means…the Cadmium Plated ones being the most common, and the last of the series.
Those with Empty Pockets may have already been on the way to filling (ie, primer, and Powder) the “Blind " Pocket ones, probably in the works when the experiment was terminated… The Fluted types are a definitve " Drill”, and the “Drilled” ones look like a make-work expedient, so as not to have to set up the “Fluting” press specially for them (maybe at a later time.)
FA tended NOT to scrap good shells unless it really had to for quality assurance purposes, but rework them into something useful (ie, Blanks or Drill dummies.)
Interesting variations…I wonder why the US didn’t adopt the French-German Bonderization process? The French did after WW II when they made the M1949 Balle “O” 7,62 (aka .30/06)— I say French-German, because the French Patented the Phosphatization process for steel sheet used in deep drawing in the 1920s, and the Germans perfected it for use in Cartridge case manufacture (Stahl-Hulse-lackiert==lacquered Steel cases) during 1940-41.
The Czechs and Romanians continued after the war, for both 7,9 and the Com-Bloc calibres, whilst the French used it in .30 carbine,.30/06, French 7,5 and even 5,56!!! and now Commercial Russian makers (Wolf etc) use the process for Boxer cases in US and Russian calibres.
Probably because (a) it was French (or German) and more importantly (b) “NIH”…Not invented here!!!