What carbines "coming home"? There is a myth that every WWII GI brought back his carbine, M1911A1 pistol or M1 rifle. In fact, it was illegal to do so (it is called theft of government property) and most vets wanted to come home, not serve 20 years in Leavenworth for the sake of getting a gun. Of course, bringing back ENEMY captured weapons was generally OK (MG's or heavy stuff could not be legally brought back), but NOT U.S. or Allied weapons.
So, until c. 1963, there were almost NO carbines on the U.S. market. One or two companies had made small numbers using surplus parts, but most of the commercial manufacturers didn't start up until after the Army release of GI carbines. And of course there was plenty of milsurp ammo, which was something of a drag on the market since there were no guns to shoot it.
(BEFORE TELLING ME ABOUT YOUR UNCLE'S LUGER OR YOUR GRANDFATHER'S JAP NAMBU, READ THE FIRST PARAGRAPH. Those were OK. But if your grandfather brought back an M1 rifle or carbine or GI pistol, he stole it, and took a lot of risk. Of course, few who did "liberate" Uncle Sam's weapons would admit it to their families; so the stories grew that some one (usually General Patton, for some reason) "gave" them the weapon, or some officer sold it to them, or they took it from a German or Japanese soldier.)