They do appear to be the right size for buckshot, but it looks like you can see the weave from the patch on one which would mean it was fired as a patched ball. Could be wrong though. You really can't say they are small so probably from a pistol, pistols and rifles shot the same range of calibers. Rifles were much more plentiful than pistols, so odds would favor the rifle. There is really no way to say anything for certain though except that they are either buckshot or small caliber round balls.