Find the load that is the most accurate for both barrels then you find your regulation point. DBML's are hard to do this because of all the variables in loading. Getting the exact same pressure on the push down, powder within a grain, nipples allowing the same amount of fire through, even slight variations in the patch lube can cause different speeds. You will have to be getting as red neck close as you can basically. And no, faster or slower will not effect regulation. They are still traveling at the same geometric line and will come to meet at the same point. Faster or slower won't affect that. Only thing speed will effect is elevation of where each barrel will hit not windage. It's getting both barrels to hit at the same point consistently that is difficult with ML's because of previously stated reasons.