I've had mediocre experiences loading cases with #4 shot, over tiny loads of IMR3031 (like .9 grn); the problem is generally the rifling twist--it's going to throw shot all over the place, no matter how you load the shell.
After a number of experiments I just switched to ye olde field expedient of carrying a few 2" .410 for 'opportunity grouse'. The patterns are still terrible, but at least I've got a pocketfull of them if I miss with the first (and second, and third...) rounds.