We model and characterize the behavior of a Q-switched fiber laser. The fiber is a doped multicore photonic crystal fiber having six cores in a ring-type geometry. The fiber laser is Q-switched using an intracavity acousto-optic modulator. Using a mode filtering technique in the far field, a mode very close to the fundamental in-phase supermode is obtained with a mode field area of $4200\mathrm{\mu }{\mathrm{m}}^2$ and a divergence of $9\mathrm{mrad}$ . Pulses with energies of up to $2.2\mathrm{mJ}$ and durations of $26\mathrm{ns}$ (limited by end facet damage) at a repetition rate of $10\mathrm{kHz}$ are obtained.