Yeah, the bazooka blocking during the mash can be a right pain. I now give the crushed grain a shake so that the flour and fine grains go down a bit, leaving more husky material on top. That way the first few scoops are a bit more husky and help with better drainage and filtration at the bottom of the malt pipe. Even better is to start the recirculation slowly with the valve almost shut, then increase it bit by bit as the mash progresses. That way the grain bed doesn't get drawn in and compact which gives the pump an easier ride. Even by the end of the mash I rarely have the valve fully open, yet still get good flow. Another thing, I would probably go with a bit more strike water for a 6kg grain bill. The recirculation works best with a slightly thin mash with more grain to be suspended. All in all, if you can get past the first 15 minutes without the bazooka clogging, the grain bed filters nicely and the rest of the mash is a breeze I find. I often do a second or third stir of the mash after 30 minutes or at 20 and 40 minutes, for the sake of efficiency, but don't stir it all the way down to the bottom of the malt pipe, so as to keep that part draining and filtering well. Happy brewing!