Bolt Catch Release

The Bolt Catch Release is the part of the AR15 lower that will stop and hold the bolt back at the point that the magazine has ran out of ammo.  It is held in place with a roll pin and has a spring and plunger to keep it in the correct position.  Here is a picture of one:

Bolt_Catch_ReleaseYou can purchase a Bolt Catch Release here (Brownells), or here (Amazon), or here (MidwayUSA), or in a Lower Parts Kit here

 

Here is a picture of the Bolt Catch Release being installed on a lower with a roll pin.

Installing AR15 bolt catch