In the waning days of WWII, the US army was looking for an upgrade to the M1 Garand. They were working on a rifle called the T20,which was simply a Garand capable of full auto fire and sporting a box magazine - really, just the later M14, using 30.06 ammunition instead of the shorter 7.62x51 which came along a few years later.
The war ended before it went into production.
During those post-war years, they began work on something called the T-25, which had some similarities to the Garand, but used the inline stock of the FG-42 to tame muzzle rise in full auto, which was always the issue with the M14 which was eventually adopted. Why this rifle wasn't adopted is an interesting story.