If they gave the order to confiscate guns, do you really think most of those federal agents would bite the hand which feeds them? Or just rationalize and follow orders?
For most of these folks, this is the best job they ever had and will ever get. Most of them, no kidding have soft science degrees and would hold jobs as a receptionist or clerk (~$40k), teachers (~$50-55k), social workers (~50-60k), or a street cop (70-80K)... and then as a federal agent can make $110K or more easily. But their loyalty to the organization (not the Constitution in practice) and complete “compliance” is demanded. Tell them to get vaccinated and mandate this, and they will, even if they disagree personally once the pressure and risk of their job is real. There are no true values at work here, there is no loyalty to a US Constitution they are sworn into to protect (most don't even know what it says!). It's a mercenary mentality and their leaders are all political hacks.
Be really careful. We watch movies and make fun of the dumb Nazi's just “following orderz.” But we are no different.
When (if?) the order to confiscate comes down, I think you’ll see the Feebs claim that they’re an investigative body. The heavy lifting will fall to others, probably not Feds.