I was out sailing a couple of weeks ago and the wind rapidly changed from a consistent 4-5 knots from the NW to a violent & gusty 20 knots from the SW in a matter of only a few minutes. Waves, whitecaps, excessive healing....all made for an exciting if not panicky few minutes. I quickly turned her into the wind and furled in the genoa while we made ready to reef the mainsail. I have a jiffy reefing set up however things did not go exactly as planned....I don't have to reef very often and this was the first time this summer so it isn't practiced a lot and with this blow we had no early warning. The weather channel had not even predicted it, so planning ahead didn't really work. Meanwhile back at the crisis at hand....I asked my wife to take the helm and try to hold her into the wind while I began attempting to reef the mainsail. I took the tension off the main halyard and began to lower the sail as I grabbed the jiffy reef line with my other hand. The boat violently shaking and beginning to turn with the wind. The boom now dropping down the mast and resting against the down-haul cleat. There was no way to complete the reef at this point. I could only do one of two things; raise the mainsail back up or drop it completely and begin motoring back to safety (approximately 40 mins away). I chose the latter and we arrived back at the slip safe but shaken by how violent those few minutes were and how fortunate that neither of us were injured or the boat damaged. So, the root of my question is this: What went wrong? How do I prevent the boom from dropping into the cockpit during a reef? Something has fundamentally changed in my set up from the last time I had to do this under similar conditions but I don't know what that is? I have a pigtail topping lift that I could have applied prior to dropping the main halyard but that prevents the boom from moving more than about 1' from mid-ship to port or starboard. That would have been risky because the gusty winds could catch us during the maneuver and potentially knock us down. Going forward and messing with the down-haul seems risky....What is the proper sequence? What should I have done differently. I appreciate your years of experience and wisdom...Thanks for your comments.