  We present a new lattice study of the discrete beta function for SU(3) gauge
theory with Nf=8 massless flavors of fermions in the fundamental
representation. Using the gradient flow running coupling, and comparing two
different nHYP-smeared staggered lattice actions, we calculate the 8-flavor
step-scaling function at significantly stronger couplings than were previously
accessible. Our continuum-extrapolated results for the discrete beta function
show no sign of an IR fixed point up to couplings of g^2~14. At the same time,
we find that the gradient flow coupling runs much more slowly than predicted by
two-loop perturbation theory, reinforcing previous indications that the
8-flavor system possesses nontrivial strongly coupled IR dynamics with
relevance to BSM phenomenology.
