Depending on how large the charge would be, the shot would likely be just inside the edge of the chamber, which would mean it had very little velocity while entering the barrel and be much more likely to allow a small amount of misalignment without encountering difficulties, so to speak. If I were forced to use this, I would sponge the first chamber as it was rotated out of battery, and load the last chamber, presumably with combined charge, sabot and shot, then rotate into battery and fire. There would never be two loaded chambers at one time. Since sponging the bore would be impractical, I would cool it from the outside with water soaked towels or something similar.
For weight reduction, I would cut away much of the material between chambers in the turret, like a fluted cylinder. Also, I believe the turret could be made smaller; there is no need for six chambers, three or four would be adequate. You couldn't safely fire this thing with all the chambers in some state of loadedness. Recoil and leakage would both cause serious problems.
