I do not believe that any of the Mec progressives will do 3" shells.
I also use a grabber for my trap, skeet, sporting clays and silo pigeon loads. I have found that #6 shot can be ornery about bridging in the shot drop tube, at least the bag I tried was a pain.
I use a size master for the stouter loads and have been hand weighing shot charges rather than dropping them with a bar, but for those kinds of loads I an generally only loading a box or two at a time.
