In the book No Country for Old Men by Cormic McCarthy, they talk about Anton specifically using a suppressed semi auto Remington shotgun. I think it was the authors misinformation as far as when the shotgun was introduced( unless there's an older Remington semi auto) because there's also a few time where he drops clip/mag bombs. The Cohen's were right in using it as far as sticking to the book though.
I’m not going to argue with the Cohen’s. sometimes anachronisms work out, and i think they did in this case. I bet they could have used an 1100, though.