How would the Swamp react to a “Million Gun March” with thousands of law-abiding Patriots showing up, legally bearing arms?
"Legally bearing arms in D.C.? Surely you jest!
The Heller case involved one armed security guard who wanted to bring his duty arm home to his high crime neighborhood. They fought that to the Supreme Court, and lost, and they started drafting new bureaucratic hurdles to gun ownership. I don't think Heller was able to get his gun for two years after the successful Supreme Court decision.
I am certain that D.C. does not "open carry" laws, so you will be violating local laws.