I just got off the phone with Art's Gun and Sports Shop , the "go to" guys on Browning A5s and asked about the inside of the receiver.
They said it was not an issue. May be due to fitting of the barrel. I don't feel anything with my fingernail.
The forearm is not cracked and the shim instruction decal inside of it is clean indicating a lower use unit.
The A5 has a slug barrel ( they are not rifled).