I will be running a direct thread can....that's what I'm trying to determine the best length/ or if I should shorten it and keep the flats. I'm going 5/8 x 24 so I'm thinking cutting it down an inch or so and that would leave enough shoulder in front of the barrel flat. Hope I'm making sense to someone....I know I can get a longer barrel and just cut the flats off but I've already ordered the 20 and want to keep em....