How does the retaining pin retain the firing pin?  The legs on the pin I recieved had it's legs spread.  When I fixed the pin to allow compete insertion the firing pin will stay in place.  Any help and/or suggestions would be greatly appreciated.
P.S. This is my first AR and I'm attempting to build gradually from parts.
Thanks

Simply limits the firing pin travel, mainly there to keep firing pin from falling to the ground uopn removal of b/bc.

Once it's (b/bc) in place the upper housing keeps/limits retaining pin from popping out under recoil, it's got nowhere to go.

Mike

It's there to prevent the firing pin shooting loose under gas pressure and back into the buffer face.

The firing pin retaining pin is a hardened steel pin, because its job is to keep that pin in the carrier when the gas pressure comes swooshing into your bolt carrier, causing the rather violent and powerful expansion of the bolt/bolt carrier unit and starting the process of unlocking and cycling the action.  The gas rings on the bolt provide the front seal on this piston, while the firing pin collar provides the back seal.  The hammer holds the firing pin tight against the back of the carrier during the initial unlock cycle, but there can still be quite a bit of pressure within the bolt/carrier assembly when the hammer's cocked down off the firing pin by the carrier, and without the firing pin retaining pin, it would shoot out like a backwards blowgun dart.

don't mess around with the retaining pin, those legs are susposed to be spread to give a tight fit.