Cheddites are not my favorite empty, which is a shame because they are everywhere. When I am loading a new load that matters, and hunting loads really matter, I send a group out for testing. With powder migration you describe they will show up a extreme variation in velocity. The nice thing about Fiocchi hulls is that you can see what is going on inside them as mine are a semi clear plastic. With Cheddites and fine grain powders you either have to go with a wad designed for straight wall hulls, like some of the Federal type wads or buy the much more expensive Euro wads. I hate accumulating so many special, single use wads so am trying to go with common wads being used for multiple loads by changing powder use.
I expect your loads would have been fine with BlueDot, if you had any on hand, because it would not migrate as much. The Winchester ball and small flake types like American Select would be off my list. I know Claybuster makes some wads in a straight hull configuration as well as the normal tapered hull configuration, but do not know if they do it for the AAred wad you are loading. In fact I am sure they did not last time I checked. You could use the Remington RP12 which seemed to give a better gas seal than the AA12R did. I use to drop about a grain less powder with the Remington wads. I just checked the Hodgdon website and that still holds true. We use to have a lot of bloopers with Sr 4756, in extreme cold weather. Bloopers are disheartening when you are hunting because your chances are so limited in numbers, you want perfection. Plus the safety issue if you are shooting a semi automatic about the barrel being clear for the next shot. Sorry for your problems. It is food for thought.
