I don't know what you mean about the Feds. Was the federal government involved in the charges in someway? If you are referring to your arrest appearing on the national database (NCIC) as well as Texas' database (TCIC) then that is all taken care of through any expunction. DPS for Texas maintains TCIC and the record of your arrest would be removed if an expunction were granted. Any future inquiries to the NCIC database will no longer pull this data from TCIC, hence it will be effectively removed from the national database as well. If an expunction is done and all entities are properly served then not even law enforcement is able to tell you were ever arrested and you are legally permitted to deny the fact that you were ever arrested.
Apparently, the FBI is the actual investigative agency for firearms-related background checks which each state must go through. The lawyer I spoke with specifically warned me that even if we got the arrest expunged in Texas, it would not necessarily mean the FBI would remove any existing info they had discovered in the process of previous background checks.
I'm really in the dark here.