Roughneck told me that trick last fall when talking about his TM M3 shotty. When I got my DE M3, I decided to try it out. At 20 feet, I got about a 3-4" spread with all the same weight (mine has a feed issue and double feeds, so 6 BBs at once). With mixed weights, I was getting about a 12" spread at the same distance. That's much more effective for CQB I'd think. The spread would probably be less with a shotty that's feeding normally, but still wider than using all the same weight.