Imagine if the WW1 store of .30'06 had been depleted
The World War One stocks were deteriorating so fast that in the 1920's the Army had to go to Congress, educate the bastards, to get money to demill the stuff. You see, Congress, exactly like the general public, thinks gunpowder lasts forever. The Army still did not get enough money, because educating Congress is just about impossible. But, by the time you get to the 1930's, any decision made on "stockpiles" was 100% bogus.
Just go to Small Arms Survey (an anti gun site)
http://www.smallarmssurvey.org/ and under the pull down menu for Regulations and Controls, Control measures, Stockpile Management. Everything there is directly related to disposing of millions of tons of old ordnance, before the stuff self ignites and explodes!.. There are reports on exploding Ammunition depots that were not cleared out, before nature (deterioration of gunpowder) cleared them out. About one Ammunition Depot is going Kaboom somewhere, per month.
I read the MacArthur memo and it was a "do nothing" decision. You know: "
life is so hard, money is so tight, we can't change because change costs money". If you have not run against this in your organization, then maybe you are a broom pusher. Even so, at some time in the future, you will need a new mop and bucket. See how management acts then. What I believe happened was whom ever was the Champion of the new replacement round, left the organization. Might have been in the Chief of Staff Office. The fact the Ordnance Board had to run the "pig tests", to prove the lethality of the 276 was equal to the 30-06, shows that the management change had occurred before that nonsense. The pig board was a worthless delaying tactic and eventually, the anti change group won.
Based on previous experience, the Army will not voluntarily make a change to its sidearm or cartridges unless Congress or the SecDef forces it down their throats. The Army user will come up with every excuse on the book not to change. While I prefer the 7.62 to the 5.56, I would have preferred the 276 to the 30-06. When he became SecDef in the 1960's, McNamara did not put up with the sort of nonsense he saw in the WW2 Army. SecDef McNamara kept firing Generals, until the Flag Officer club figured out, either support the 5.56 transition, get it implemented now, or the SecDef will retire you now. And it worked. The M16 and the 5.56 were adopted within five years, or so.
I just noticed, the Army finally reformulated Mil C 872 Rifle Bore Cleaner in 2017. Rifle bore cleaner going back to WW2 removed corrosive primer salts. Corrosive primers went out of inventory in the early 1950's. Been awhile. It is not good at all at removing powder residue, and has no affect on copper fouling. It took from WW2 to 2017 for someone to push through a spec change, that the new rifle bore cleaner finally removes powder residue and copper residue. To expect inhouse change in DoD one has to believe that a mouse can birth to an elephant.