A modified
barrel and vented blank firing adapter for a failsafe firearm suitable for training exercises and in particular for MILES exercises. A preferred modified
barrel includes a plurality of
blow out apertures spaced about the
barrel's longitudinal axis at a location adjacent to a case of a live ammunition
cartridge when loaded in the firearm, the
blow out apertures venting from the case a substantial portion of
combustion gases produced by firing the live ammunition
cartridge; a laterally vented blank firing adapter for producing flash at the
muzzle upon firing of a blank ammunition
cartridge; and a gas port in the barrel sized for admitting to the firearm's
cycling gas tube sufficient
combustion gases produced by firing the blank ammunition cartridge for implementing
cycling operation of the firearm. The laterally vented blank firing adapter preferably includes a cavity for
trapping projectile material when a live ammunition cartridge is fired.