Big public demonstrations (marches, sit-ins, protest rallies, etc) are an effective tool if your agenda appeals to those who do not have regular employment. Past examples are the movements to Save The Whales, End Commercial Logging, Protest a War, Protest Wall Street. If your agenda appeals to college students and the un-employed, a street protest is a good tool. I am not trying to disparage college students (I was one once) or the unemployed. But those people can't donate money to lobbing groups, they can't donate to election campaigns, so the only way to make their voice heard is by demonstrating.
If the Government were trouncing the rights of Golfers, NFL-season-ticket holders, Boaters, Scuba-Divers, or Equestrians, I seriously doubt that a protest demonstration would be effective, because all of these people would tend to be gainfully employed with busy lives. The same is true for firearms enthusiasts... A hundred million people may own a gun, but the number of enthusiasts is smaller, and gun enthusiasts tend to have an income generating job or profession..... It is not that easy to just "march on washington". It is a lot easier to make phone calls, write letters, and donate cash to the cause...