Sounds like an Armalite bolt carrier. Tech note #5 in the library covers this and how to remove stuck bolt.
http://www.armalite.com/images/Tech%20Notes/2015/Tech%20Note%205,%20Errata%20Sheet%20for%20AR-10%20Rifle%20031230.pdf
CAM PIN FIT: Easy does it! Insert the cam-pin straight into the carrier with the flat edge of
the pin against the carrier key (you don’t rotate it 90 degrees like the M-15 cam pin). Until parts
are loosened by breaking them in, tight tolerances on the AR-10 sometimes require use of a flat
tipped screwdriver or other suitable object to slip the cam-pin past the bolt carrier key. The cam
pin must never be altered to provide clearance.
CAUTION: INSERTING THE BOLT: WHEN ASSEMBLING THE CARRIER GROUP,
INSERT THE BOLT INTO THE CARRIER ONLY DEEP ENOUGH TO ALLOW THE
CAM-PIN TO BE INSERTED. IMPORTANT: THERE IS A GROOVE INSIDE THE
CARRIER AT THE BOTTOM OF THE GAS CAVITY. INSERTING THE BOLT TOO
FAR INTO THE CARRIER WITHOUT THE CAM PIN IN PLACE CAN, IN SOME
CASES, ALLOW THE MCFARLAND GAS RING TO EXPAND SLIGHTLY INTO THE
GROOVE AND JAM THE BOLT IN THE CARRIER. REMOVAL CAN ORDINARILY
BE PERFORMED BY WIGGLING THE BOLT SLIGHTLY, BUT IT MIGHT REQUIRE
DRIVING THE BOLT FORWARD WITH A BRASS ROD. THIS CAN DAMAGE OR
DESTROY THE RING. THE ERROR CANNOT BE MADE WHEN THE CAM PIN IS
IN PLACE.