My dad dumped the M1 carbine and carried an "abandoned" M1 Garand for the duration of his 2 1/2 years in the South Pacific (he was an 81mm mortarman). Said he "couldn't hit the broadside of a barn" with the carbine. Every M1 carbine I have fired in my lifetime could easily take out small windows in a barn from 50-100 yards away. I do not know how or why THAT rumor got started, as he is gone now, and I never wanted to get into the argument with him when he was alive.
I've served with a couple of guys who fought in WWII, from what they've said, and from my understanding of fighting off enemy combatants, it's preferable to take them out long before they get within 100 yards, and the M1 Garand was good at taking out targets beyond 300 yards.
I served with one guy who was with 101st, he was one of the "Battered Bastards of Bastogne", served in Korea with the 101 as well, was 1 of only 10 who survived when his unit was wiped out. The biggest problem, he said, they had was that they just didn't have enough ammo to kill them all with, so they ended up beating their brains out with their weapons until they lost their weapons somehow, then he crawled onto a passing tank and beat them off with a cheater bar until it got dark so he could slip away under the cover of darkness.
He served in Vietnam with the 101 as well, different war, different rifle. He wore 5 battle stars when he retired with more than 40 years of service, most of it with the 101st Airborne.
But I digress
I think the biggest myth I've heard is that you just sit back and shoot at the enemy when he stands up like a pop up target.
Truth is you hardly ever see who's shooting at you, and if you do see him you're going to have lock arms with him and kill him or he'll kill you.