This is NOT intended as ANY sort of put-down, or any desire to stop the discussion. We find many 'odd' assemblies today. Some are so goofy that they can be dismissed out of hand, but others are quite logical, and MAY well be (within reason) "correct". The arms have passed through too many hands, with no chain of custody, to be 100% certain in all cases.

Bottom line: The personnel of the Ordnance Department were trying to field the most up-to-date TOOL that could be provided to the soldier, and that involved swapping some parts, not always at the same time, or place, and not always with the same parts(!) though they WERE also striving for interchangeabiity. They had absolutely NO thought that they might be confusing future participants in a hobby that had not even been invented yet!

End of rant  :)  :)