The skirt is longer to hide the gap between barrel shoulder and flash hider on AR-15, M16, and M4 rifles. The ring is groove based. That works well for the integration of a Blank Firing Attachment (BFA) used by law enforcement trainers, and permits installation of the Smith Enterprise M4...
BLANK FIRING ADAPTERS There are two different blank firing adapters for the AR platform rifles. For rifle length gas systems (nominally 20" barrels) the correct adapter is the M15 red blank adapter, assembly 12002800 with a vent hole of approximately .0635" (#52 drill). For carbine length ...
The simple assembly and solid lock-up of the adapter creates a rock-solid stock with standard OEM parts, in the deployed position. Aside from actually shooting the firearm, and potentially adjusting the way you charge the weapon (to avoid busting your knuckle on the hinge), there is little ...