They were beech loading. The battery gun used a long strip that held cartridges much like Maynard cartridges on it that was dropped into the rear of the gun then butted up against the breeches. They were fired by a percussion cap that ignighted a train of powder.
That big Vandenburg was also breech loaded and fired paper cartridges. I suspect the Vanden berg may have been the source of the idea for the French Millteusse (sp?) (Come on guys I can barely do English so give me a break on French, eh?)
Apparently the Billigquist battery guns actually worked rather well for guarding bridges or the moats of fortresses.
See, I did go back and suffer through the whole thing.
-kBob