Hoping it shows up on this pdf...
It is part 29 the locking latch - you know it as the two cone shaped protrusions that stick out of the breech face.
The wear occurs between them and the matching holes in the barrel mono-block.
Beretta has oversized ones that they use when servicing the guns - there are incremental sizes that allows this to be done several times - thus extending the life of the gun while keeping repair costs down.
Part 27 (2X) the hinge pins can also be replaced with oversized ones if the mono-block & barrels ever come 'off face.'