hi, i try to find which mob drop this gun, but nothing specified on entropedia... so if someone know and want to share, it would be nice.
Sal'diresh's Vault 10? Several Piron -62's reported, although not pbr but who knows if that's the end of it: http://arkadiaforum.com/threads/saldireshs-vault-mob-loot-tables.12291/