Changing the composition and voting system of the Security Council, in an effort to increase the institution's global legitimacy, is proving to be one of the most difficult hurdles to overcome for the global community of states represented in the United Nations (UN). This paper demonstrates that due to institutional hurdles, it is considerably more difficult today than it was in the early years of the UN to reach a winning coalition in the General Assembly to secure Security Council reform. In addition, the paper analyzes the effects that adapted patterns of voting, as prescribed by recent reform proposals, would have on the distribution of power among UN member states in the Security Council and on the probability that this institution can form a winning coalition, i.e., reach decisions. Our power and decision capacity computations are based on (modified) Penrose-Banzhaf-Coleman measures.