The U.S. military has stood perpetually accused of not fielding new weapons to troops fast enough since at least the Civil War, when the Union Army took years to replace muzzleloaders with obviously superior repeating rifles.
Benjamin Franklin nailed it when he said, "Fatigue is the best pillow." True story, Benny. There's nothing like pushing your body so far past exhaustion that you'd willingly, even longingly, take a nap on a concrete slab.
In 1968, SEALs serving in South Vietnam reported to the Navy that they needed more firepower. Back in the United States, the service’s engineers rushed to help, crafting various weapons and accessories, including some particularly weird looking magazines.