We have investigated the dynamics of magnetic domain walls in three epitaxial garnet films withgvalues of 1.07, 4.8, and ≳30, and having wall mobilities of 880, 930, and 820 cm/sec Oe, respectively. Bubble collapse measurements in the films withg=1.07 and 4.8 showed velocity saturation with the approximate values 1500 and 8000 cm/sec, respectively. The film withg≳30 showed no saturation, and velocities up to 6×104cm/sec were observed. These results are consistent with the expected increase in the Slonczewski and Walker critical velocities with increasinggvalue. Largegvalues make it possible to operate magnetic bubble circuits at higher frequencies than is otherwise the case.