The feds showing up at your house about a trigger or a machine gun is something very different than a self-defense shooting.
People responding to a shooting are going to be making decisions that could impact the rest of your life, and certainly impact your finances. From the responding Officers to the detectives, to the DA.
If choosing not to speak to Officers after a shooting is your plan, that's fine. But it's only half a plan. The other half of the plan is to be able to get an attorney to talk to you, right then. Without that half of the plan, it's like any other half azzed plan.
If I was in a shooting I know enough to know if I need an attorney or not. However, if a federal agent was asking me questions about an item I have, or have had, I would want to call and talk with an attorney before saying anything to them. Keep in mind a Fed can charge you with lying to a Federal Agent whether you are charged or had anything to do with the original issue they were investigating.
So if you have purchased one of these triggers they have deemed "machine guns" you might want to contact an attorney now, or at least do your research on attorney's to see who you are going to call. "Show me a search warrant" doesn't bother cops, they hear it all day every day. They may have a warrant, in which case they won't need you to say anything, or they may be able to easily get a warrant.
Joe Biden and the BATF are playing a game. It's a game where they put as many gun owners in federal prison as they can, or they destroy them financially if they can. And every day they get to go home no matter how the game goes.
Civil disobedience is probably not the stand you want to take on these charges.