AFAIK, the E2 stock, in conjunction with a lot of other items, was intended to make the M-14 reasonably accurate in hand-held full-auto mode.
For the most part, this failed to work as desired. No expert, but I've never heard of an M1A owner stating that his E2 stock was better than a good wooden stock, or a good GI syn stock.
The slip-over, drilled, GI muzzle comp works pretty well as regards keeping the muzzle down during hand-held rapid-fire, if you can find GI examples. Take them off at dark, because they defeat the flash-suppressor feature on the rifle.