Bushmaster AR-15 Bolt Carrier Design

[FPrice]

I had to swap a firing pin yesterday (selling one Bushmaster to afford another) and noticed something different about the bolts carrier. The bolt carrier on my new A3 16" barreled BM had some metal removed on the bottom side. You could see the last half inch or so of the firing pin when it was installed. On the older bolt you could just barely see the end of the firing pin.

Was there a change in the bolt carrier design?

 

[Bartholomew Roberts]

The older carrier had a shrouded firing pin like the M16 carrier. Some manufacturers believe this offers extra reliability and offer AR15 carriers with the firing pin shrouded.

On the Bushmaster, the metal is cut away to expose the shoulder of the firing pin. The idea behind it is that this carrier is harder to use in a full-auto weapon.

See this link for details:
http://www.ar15.com/content/legal/AR15-M16Parts/