CARRIER...not bolt. Compare the carrier internal structure,
between tail of bolt and flange of firing pin.

Well, go ahead and eyeball the bolt, too...low hanging fruit, easy to compare. Might was well throw the firing pin in, too.

Semi-auto and select fire carriers are different at back end...if carrier acts to prevent firing pin protrusion on an unlocked bolt, that's a feature that would not logically be exclusive to a semi- carrier.