Any mix of lead shot is safe so far as pressures go, but it takes some tuning to get a pattern, if that's what you want from the fine shot. For buck shot to print good patterns it must lay in stacks of three or four, which fill the case closely, maybe even two, with the next stack of two crosswise. If you want to have large buck print a nice pattern, center each ball in shot buffer and stack the shell full. The load will be light, but the balls will leave fairly well centered with the bore and print nice tight patterns. Pressures are touchy with shotguns, so find data that suits the shot charge weight you are putting in. I see no reason why the proper size shot which filled a snug row all the way around your buck ball wouldn't do the same as fillering with shot buffer or stacking as for proper buckshot loads. However the shot wouldn't be worth much for large game if under #4. Better to find the goose shot which stacks like buckshot. It probably isn't well known, but from a 12 guage, #2 shot will kill deer instantly out to 40 yards using a full choke and taking side of the chest, neck or head shots. BB or larger in your 410 will penetrate to deadly depths, but won't have 12 guage multiple hit quaantity. But for close rande defense etc I would trust it. I stated lead shot above. Don't mess with steel shot if you value the barrel..