Most of the grunts didn't even USE the name M14A1 because that name was only really used by logistics and that variant never really made into common use. Ater the M16A1 came out, folks didn't like calling the M14E2 the A1 because it was confusing at that point. They continued to call it the E2 because that was clearly the experimental version that they were fielding in the early war years.
I guarantee you, if you said M14A1 to most gun scholars or veterans, they'd go "huh?"
Or think it was the Semi version (wrongly of course).