d508, I'm not going to quote your post, for the sake of brevity, but H-5!!!
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I have to stop at this point, but the Sherman tank was used again in Korea, as were WW2 type infantry rifles.
I know you're quite a military tech buff, but a lot of the things you and others find scandalous are somewhat misstated, and flowed from reasons other than simple budget or political constraints, such as wartime resource allocation and the role of the technical boards within the War and Navy Departments as well as issues like wartime resource allocation and the use of not-unlimited logistic assets to move materials, equipment, and units.
Just to discuss the last little bit, for instance, "Sherman tanks" takes in such a huge variety of vehicles and armament suites that the only thing they really have in common are the words 'Sherman tank.' The ones used in Korea were not intended to be the primary tank for the theater but were refurbed and fielded until enough M26s and M46s could be fielded...and on top of that, the Shermans used in Korea were the wide-tracked HVSS models like the 'Easy eight' (M4A3E8) with a high-velocity 76, and fully-sloped (47-degree) frontal armor, fielded initially only in December 1945, and quite superior to even the best common models of the Panzer IV and StuGs, the actual mainstays of the Wehrmacht, and able to effectively engage Panthers if at some disadvantage (Though the Panthers were being so heavily attritted by Allied air and artillery dominance at that point that they were unable to effectively counter the -E2 and -E8 Shermans). A lot of dumbasses who play computer games, take the History channel as gospel, and have never been inside a real tank call them 'Marginal improvements' over the cast-hull VVSS narrow-track 'Ronsons' fielded in 1942. These people are dopes, the only thing the M4 and M4A3E2/8 have in common is a general shape, six road wheels on each side (Using, however, utterly different track and suspension systems), but practically nothing was interchangeable between them, everything else - size, armament, armor thickness and placement, ground pressure, and powertrain - were completely different.
In Korea, the vanishingly-few tank-to-tank encounters involved T34/85s on the Red side, about all the Norks had, and not in huge numbers. While the T34 had fine mobility and a good ballistic shape, its 85mm main gun was only roughly equal to a German 75L48 (Not the L70, though) or the American 76mm (And nowhere near the same league as the 90mm on the M26/M46), their tank-to-tank commo was hand-signals and flags rather than FM radios, and their ability to train the unstabilized main gun was mainly a cranking job rather than the powerful and reliable hydraulics on the American tanks, which also had stabilization systems. The entire T34 family, and its descendants until the T64 and T72, used dry-pin track with no grousers which both wore out more rapidly than bushed track and had markedly inferior climbing ability in the hilly Korean terrain. The Christie-type suspension had been a huge innovation in the BT series tanks, continued with and additional road wheel and beefier construction in the T34s, but it was quite difficult to service when one of the massive coil springs broke and consumed considerable internal hull space; the Sherman's HVSS and 23" wide tracks were at least competitive in mobility and much more easily serviced, being entirely external, and the M26/M46's torsion bar system was its equal in deflection and thus mobility, and quite superior in serviceability as well as availability of the full hull width for internal storage of fuel and ammo and large powertrain components, a deficiency the Soviets fixed with the T34's successors by switching to torsion bar suspension.
The M26 was actually fielded for combat testing in the final few weeks of the war in Europe (Despite GEN Patton's and the ARMY's resistance, NOT that of the politicians), and came out approximately even in a few encounters with Tiger Is; the primary difference between the M46 and the M26 were in the drivetrain and placement of the final drives, not the turret, armament, or frontal armor, and even the later M47 and M48 were basically improved M46s, still with 90mm main guns. Even the basic M60 turtle-turret was the same casting as the M48 turret, US tank design was highly evolutionary until the MBT70 program.
In the Pusan perimeter battles, though, the high tide of Nork armor advances, the thing that actually checked them was the arrival in theater of the 'Super bazooka,' i.e. the 3.5" bazooka, after the WW2 2.36" bazooka had proved ineffective (For reasons concerning which it is difficult to find much factual information, since it had proven quite effective against German tanks that were equally-well armored in the ETO); the 3.5" bazooka was to all intents and purposes a US improved copy of the 88mm
Panzerschreck, itself a German improved copy of a captured 2.36" bazooka.
As far as the use of WW2 rifles is concerned, the Garand actually remained a world-beater through the end of Korean hostilities, the Norks and ChiComs were armed almost entirely with Moisin-Nagant pattern bolt-action rifles or PPSh/PPS patterned SMGs. Despite the nominal adoption of the Simonov's SKS and Kalashnikov's AK by the Red Army well before the Norks crossed the 38th Parallel, they weren't exactly handing them out to the farm team henchmen then or for quite a few years afterward. The awkward 'en-bloc' loading system with its 8-round capacity was a product of Army board requirements, one in which both industry and politicians had completely clean hands. Despite its weak hitting power, the M1 through M3 carbines, as well as the BAR and the entire line of German
Sturmgewehre and literally everyone's SMGs, had proved the concerns about the fragility of removable magazines to be an entirely illusory problem, but in the absence of driving need, the Garand's successors like the BM59 and M14 were still gestating, as were the quantum jumps like the FAL and AR systems.