A real USGI M14 is selective fire and heavily restricted even though older than 50 years.
There are very few live legal transferrable M14s. I see prices $15,000-$20,000 discussed but none actually for sale.
The M14 is a select fire battle rifle. A transferable M14 well run 15-20K depending. Then you well need to feed it at $3 a second. In military service many of the M14's had the selector switch removed so they would only fire semi-auto. The only way I have gotten any kind of control in full auto is in a prone position and using a M2 bi-pod. It's one hell of a bullet hose.