Like Geno I too suspect this is a perfectly legal search and investigation. It is not the least bit odd or unusual that there were no charges filed yet. Charges are not going to flied until they have had an opportunity to evaluate the evidence they have collected to see how it fits into their investigation and evidence of criminal activity. Sometimes that requires evidence being tested through Criminal Laboratories and that can sometimes take months or in some case even years before the prosecution is ready to proceed with charges.
Before I retired I often had cases that resulted in the execution of a Search Warrant, to collect evidence, that then went nearly the full two years before the expiration of the Statute of Limitations before I got the Lab Results back and filed the charges. The bottom line is in the fact that charges rarely come at the same time as the search so I see nothing unusual in the actions of this investigation, even though I don’t put a lot of trust in the actions of our current Federal Level Administration, especially when it involves firearms investigation.