Eventually, it was claimed they were serving a search warrant, which was testified to in the hearings before Congress to have been for grenade casings which had been observed by a delivery driver in a ruptured package.
Those casings which would likely have been used to make inert novelty 'grenades' (complaint dept, take a number) by the gun show cottage industry contingent there were not in and of themselves a prohibited item.
The same week as the raid, the "Sinful Messiah" tabloid-style front page newspaper stories came out, alleging that Koresh wash having sex with children and spanking babies...
Allegations of a meth lab on the premises were made as well.
Neither of the second two were in the purview of the BATF, the former dubious, simply because you do not arrive with two cattle trailers full of agents and the media in tow to simply serve a search warrant.
As the ATF had been invited by Koresh to inspect the business, (which dealers must, by law allow) and declined earlier, it seems strange they did not just drive up in the ordinary fleet of suburbans and produce the warrant and do the search.
No one present at the door had a copy of the warrant, either, which seems strange if that is what they were there to do.
FYI, the Davidians had a few cottage industries to generate income, one was the FFL dealership which did the gun-show circuit, another was a christian rock band, and yet another (off premises) restored cars and did automotive bodywork. The firearms related business was only one of those businesses.
I always found it interesting that BATF guys, even after copious amounts of adult beverages wouldn't cop out to everything they knew.
I suspect the whole truth isn't out there yet.
10%-15% of the true events at Waco are now in the public domain. That will soon change. The fire, first and formost, was a destruction of evidence, and secondly a mere diversion. Is John Q. ready for the truth? Can they handle it? Or do they need to wait until 2017?