Never saw a vierling with a rimfire barrel unless it was as an einstecklauf. To my knowledge, most often the sub-bore cartridge was 5.56 Vierling, a centerfire cartridge. They're also more than handy with most weighing less than 8 lbs. Less than a lot of scoped, bolt rifles. Cape gun is generally the British term for SXS combination guns. Generally, in the British version, the shotgun barrel is on the right and the rifle barrel on the left. Continental combinations are usually the opposite, rifle on the right, shotgun on the left. On the continent it's generally combination gun or "Buchseflinte". In the US, SXS combination guns were uncommonly made as one sees very few. Not so on the Continent or in South Africa and, there is quite a few in the US, if you know where to look, brought over as WWII trophies. They were made long after the BP era came to an end.
Any kind of combination gun never was exceedingly popular in the US, even when hunting was wide open and seasons non-existent. I always thought that unusual as they seem a perfect....combination. I can understand it today where laws from state to state vary so much and, with what kind of firearm one can hunt with during a season.
I don't believe combination guns, drillings or vierlings came about because of a limit of "one gun per household". I'm fairly certain that's been laid to rest as a reason for their development. Their utility as game keepers firearms and for northern European hunting, whether driven or not, no doubt influenced their development. None of the 3 were ever inexpensive, certainly beyond the means of a peasant and, I don't recall ever reading where the well to do businessmen, Junkers or various "royal" houses were ever limited to one firearm.
