It's impossible to carry the M14 shouldered with a magazine inserted. Also, the Manual of Arms for the M14 includes the command "Make ready for inspection" which includes removing the magazine and operating the action to ensure the chamber is clear. Only then does the inspecting officer/NCO take the rifle.
Wonder why they don’t still carry M1 Garands then, or the M1903, as in years past. No external magazines to get in the way.