Let 'em get in close. Don’t waste ammo. Get your share! Remember, you don't hurt 'em if you don't hit 'em.
Source, in full
Addressing troops on using ammunition with accuracy (November 1950), as quoted in One Bugle, No Drums: The Marines at Chosin Reservoir (1986) by William Hopkins, Ch. 5 : Trouble at Kojo, p. 61; also quoted in The Marine Corps Gazette Vol. 47 (1963), p. 46