My dad hated his. He bolo'd during qualification. Everybody in his group shot like shit. Earlier, in basic, he shot well with the M1 Garand. So, he liked the Garand and hated the carbine.
Fast forward to a few years ago and I'm watching Ian McCollum's "Forgotten Weapons". He had this guy on there named Ken Hackathorn. Ken goes on to explain that after WWII, all the carbines went in for rebarrel, then get taken down for parts. Then we needed them and they all got slammed back together. Mismatched parts from all the makers, sights not tuned to the rifle because they used to be on another rifle. And, not adjustable. It gave the M1 carbine a bad reputation.
Anyhow, I explained this to my dad. Even got him to watch the episode on YouTube. He was shaking his head going, "No goddam wonder..." I asked if that meant he was going to go out and buy a good one? "NO! Goddam pieces of junk!", He said. I laughed. I've shot some good ones and understand way better what they can do.