I carried and qualified with 5 different M14 Rifles in the late 1960s, it was still the standard rifle in Europe until after Vietnam due to caliber standardization.

Only one (1) of them had the selector on it, and this was on a M14E1 (later M14A1) rifle.    This is the one with the straight-line pistol stock and special sling. Even with the muzzle brake one had to really hold onto the sling and fire from the prone (or foxhole) to achieve any accuracy.  Fitting or even having the auto parts was a court martial offence.

I qualified expert on this version as well as the standard versions, but don't recall the standards for the automatic version other than we fired from the foxhole.

Recoil isn't bad firing from the bipod from a hole.  Actually you're spending so much time controlling the muzzle that whatever the recoil might be isn't noticed.  Firing this rifle from any other position is pretty uncontrollable:  Use the same techniques as any other AUTO.  Hold low and try to walk the bullets up to the target.

There's a full auto M14 at one of our local shoots, some sort of "dealer sample" I imagine.  It can't hit diddly when we shoot at 9"x9" steel plates at 75 to 100 meters.  Nor can the FALs or MP5s.  Little .22LR full-auto with a top mounted drum is the only full auto I've seen which can hold on a target this size.

-- Chuck