correct again, ouch not a good day for me.
The multiple bullets on a row configuration is know to me, but i doubt it was used to often. I read that the bullets tended to get stuck inside the barrel?
On the other hand, i have seen replica's beeing fired without trouble. (not because they where replica's but because there is a lot of sense in the idea).
if i remember correctly (and that is pretty hard for me today apparently) i recall a firearm which used a trail of gunpowder in the middle of 2 barrels. With multiple holes in the barrel with a corresponding load of powder and bullet lined up.