Didn't the flintlock Brunswick rifle use a belted ball, too? I think the "Sharpe's Rules" series about the Peninsula Campaign on PBS featured the Brunswick, but plot emphasis was not on the particular rifle so much as that the company of riflemen was an anomaly in an expeditionary force otherwise armed with smoothies.
BlueJacket, I'm pretty sure that the Sharpe's Rifles series characters were using the Baker rifle which had more conventional rifling. See Squire Robin's posts on shooting his original Baker.....a wonderful piece of history!
I, too, had brought up the similarity between the two-groove rifling in the rifle shown in this thread to a Brunswick in my earlier post. Coincidentally the Brunswick was of German design.