I've shot 155, 165 and 180's in my 27 and it's dead on the money with the heavy 180 loads. Seems like the lighter the bullets get the worse the accuracy. Mine really likes the Hornady 180 grain TAP. I've always liked lighter bullets in the 40 but I believe accuracy comes first. I would rather hit him with a 180 than miss with a 155. I know the 180's are good I just like light and fast. But I will stay with heavy and slow for my 27.