sounds like you are one of the guys who never got the 20 m14 headshots using laser dot?
either way. the perk is nerfed alot. if u are a really old player.
And yeah you gotta be out of practice. even the perk has is a litle harder to use now then before. it's still not "super hard" i'm easily getting 20-30 straight headshots with the m14 without a single miss. or using the sights. so it should be all fine and easily surviving solo hard/suicidal using the m14.
I have to be honest and say that the m14 is harder to aim than like the LAR. so it should use some more practice but the reason for that is the recoil and rapid fire. and by no scoping the M14 is shorter and more "stump" ending to the gun than the LAR. so it is harder to see where your in middle screen aimpoint is!