  We propose a scheme to produce ultraslow (3+1)-dimensional helical optical
solitons, alias helical optical bullets, in a resonant three-level
$\Lambda$-type atomic system via quantum coherence. We show that, due to the
effect of electromagnetically induced transparency, the helical optical bullets
can propagate with an ultraslow velocity up to $10^{-5}$ $c$ ($c$ is the light
speed in vacuum) in longitudinal direction and a slow rotational motion (with
velocity $10^{-7}$ $c$) in transverse directions. The generation power of such
optical bullets can be lowered to microwatt, and their stability can be
achieved by using a Bessel optical lattice potential formed by a far-detuned
laser field. We also show that the transverse rotational motion of the optical
bullets can be accelerated by applying a time-dependent Stern-Gerlach magnetic
field. Because of the untraslow velocity in the longitudinal direction, a
significant acceleration of the rotational motion of optical bullets may be
observed for a very short medium length.
