  Energy spectra of particles accelerated by the first-order Fermi mechanism
are investigated at ultrarelativistic shock waves, outside the range of Lorentz
factors considered previously. For particle transport near the shock a
numerical method involving small amplitude pitch-angle scattering is applied
for flows with Lorentz factors $\gamma$ from 3 to 243. For large $\gamma$
shocks a convergence of derived energy spectral indices up to the value
$\sigma_\infty \approx 2.2$ is observed for all considered turbulence
amplitudes and magnetic field configurations. Recently the same index was
derived for $\gamma$-ray bursts by Waxman [Astrophys. J. Lett. 485, L5 (1997)].
