The 222 Remington Special was a Stoner design and tested during 1954-56, this became the Rem 223 and military 5,56mm (there is a slight difference between these two cartridges).
The 224 E2 Winchester was tested during the 1957 trials and loaded to 3300 fps.
Also shown is the British4,85x49 mm (tracer) for comparison
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