That's easy. The answer If a LEO asks, "Do you have any guns in the car or anything I should know about?" is:
No, there is nothing in my car you need to know about.
And, when he frames another question concerning guns you simply ask, "why, am I being detained?"
When he says no that should be the natural end of that conversation because he is just fishing with his questions and doesn't intend to search you anyway.
You generally run out of time before you run out of ammo.
AKA Richard Cramden