I’ve never fired a real M-14 but I can’t imagine what it’s like trying to keep the muzzle down while firing .308 caliber on full auto.
Thats why you have that “shoulder thing that goes up” !
Not too bad if you've got the bipod on- another pound and a half- and the accessory compensator, and keep the bursts short and use the sling. I liked the M14, but it's nowhere as controllable in full-auto as a German G3. Or, for that matter, a 15-20 pound BAR.