The M1 Carbine is the standard by which all PDWs are measured.

[montana]

Such "bad thinking" was not limited to the bureaucracy. John Garand also made the same error, and originally opted for the "failed" gas trap system on the M1 rifle. https://www.forgottenweapons.com/gas-trap-m1-garand/

True, but kind of explains the concept of drilling the barrel as being some what of an un-proven concept for the time.

The 8-rd clip was not a bad choice, but only because the vast majority of WWII opponents were still using bolt-action rifles with 5-rd and 6-rd clips.
That the en bloc clip was usable, doesn't change the fact that it was an outmoded feed device, inferior to detachable box magazines for military use.

Even before the 1930s, state-of-the-art, self-loading rifles were using detahable magazines.

True, but the US and other nations have had a bad habit of manufacturing poorly constructed magazines for firearms, degrading the reliability of an otherwise reliable weapon system. In a time before nations could just print money for weapon systems, economics played a bigger role in firearm development. Conservative economic thinking ruled most nations during that time period. The German tank warfare idea concept was actually a British officer's idea idea https://www.counter-currents.com/2015/08...1878-1966/ ignored by his own nation and borrowed by the Germans. The French idea of static warfare during WW2 was another blunder of old ideas ending in disaster. The en block was probably considered the best alternative, considering the problem Winchester had using a modified BAR magazine for their experimental mag fed Garand. The M-14 was very expensive and took way too long developing a mag fed Garand.

Even before the 1930s, state-of-the-art, self-loading rifles were using detahable magazines.

Federov Avtomat - 1916





Ribeyrolles - 1918





Tipo Terni MAF - 1921





Czech ZH29 - 1929

Other than the Czech ZH29 - 1929, these firearms were not known for reliability or dependability compared to the tried and true clips and en block charged firearms. Like the The French RSC 1917 rifle, it was innovative, but not yet perfected or proven until the M-1 Garand.