Yes, a sit-in may be an effective way for Congress to get a vote on an issue in some instances. This brings the issue to national attention as well as the need for a vote on it. The attention that the sit-in receives helps to put pressure on Congress. Thus, sit-ins are effective for publicizing an issue.
With some of the least effective Congresses on record, 2016 Democrats are forced into some grave positions. Hearkening back to the sit-ins for peace and civil rights at earlier points in our history, the Democratic sit-in is a non-violent means of bringing to light a crisis in contemporary American life and forcing members of both parties to do their job.
The Democrats sit-in regarding a gun vote will prove effective in getting Congress to vote. It is a hot button issue, and there was an incredible amount of publicity. Many people have sided with the Democrats, and Republicans will be anxious not to look foolish. The Republicans looks uncomfortable and out of control.
Yes, I think that this is an effective way for Congress to get a vote because the sit-in helps bring more attention to the issue and shows that members of Congress are working tirelessly to get something done. The worst mass shooting in American history occurred and Congress still failed to pass legislation making it harder to get firearms, which is incredibly sad.