Muzzle Blasts accepted/published my fiction story about a rabbit hunting fiasco (didn't get a rabbit but had good adventures.) Anyway, I've always shot a .50 flinter, and the time period I live in is mid 18th Century when I am a long hunter with one gun. Most roundball guns shoot the same point of impact at 25 yards with close to half of your deer load. A little range time will give you the specific accurate small game powder charge. No need to change anything but how much powder. Of course wherever the lesser load hits a squirrel is not edible. It's all good fun. Oh, once shot a turkey with a half load, just aimed behind the breast.