"I might be wrong but I think the 30-06 machine gun ammo was too hot for the Garand."
Sorry, Hawg, but you're wrong, but with a POSSIBLE grain of truth...
It's a somewhat complex story, and maybe true (it is disputed by some) or may be false.
In World War I, the standard .30-06 loading used a 150-gr. flat base bullet for both rifle and machine gun use, the Ball M1906 round.
One of the outcomes of the war-time experience was that the ammo simply didn't have enough range for long-distance harassing fire with machine guns.
There was also the issue of the jacket material (cupronickel) fouling barrels.
In the early 1920s a new bullet, a 172-gr. boattail, was adopted as the .30-06 Ball M1. It gave greatly increase range (nearly double!), but it also made just about every military firing range obsolete. Supposedly one of the first times the ammo was used for training a homeowner who previously had been well out of range had his house severely damaged by bullets overshooting the range.
Here's where the story is disputed...
At the same time the United States was developing the Garand rifle. Supposedly, once the order came down to stick wtih the .30-06 (as opposed to the .276 Pedersen), Garand had a lot of trouble adapting the M1 to the heavy bullet load, while it worked fine with the ligher bullet load (those WW I era rounds were still being used for training as stocks of the Ball M1 were built up).
In 1938 or 1939, the decision was made to switch back to what was essentially the Ball M1906 round, but with a guilding metal jacket.
This solved any issues there may have been with the Garand, but the military had to figure out what to do with nearly 2 billion rounds of Ball M1.
So, the decision was mark it for use in automatic weapons only.
It was issued primarily for use by infantry but also in aircraft machine guns where the better ballistics and heavier weight were a distinct advantage.
Once those stocks ran ough, though, they were replaced with Ball M2. By then, though, it really didn't matter because combat ranges were nothing like they had been in WWI, and aircraft had largely moved to the .50 BMG round.
"The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza
Baby Jesus cries when the fat redneck doesn't have military-grade firepower.