The BD 14 is all but the perfect Bockdrilling, I will get there one day…
I would not buy a BD14 that is more than a couple of years old. They had an abortion of time getting them to work, the first few generations sucked.
Drilling 101:
Dri = 3 so 3 barrels.
Vierlings have 4 = vier our four barrels.
Bockdrilling is a vertical drilling. To some people a Blaser d99 is a bock drilling. I do not believe it is, it is just backwards. Think over under shotgun. Or Bochflinte
Kugeldrilling is a all rifle barrel drilling
Doppenbuchsdrilling is a double rifle drilling.
You could also have a Doppenbuchsbockdrilling. Double rifle with 1 shotgun barrel in the over under configuration.
Or a Bochkugeldrilling 3 barreled over under drilling.
Cartridges
6.5x55 yes, but not common. Mostly sold to Scandinavian countries.
7x57 probably not, but yes to 7x57R
7x57R would be super common
8x57R super common
8x75R not impossible to find, but not common in export guns
There is another 7mm Vom Hoffe round for Rimmed cartridges really rare
10,3x60R probably not commonly exported, but they exist popular in Switzerland
9,3x57R popular in Scandinavia
7x65R yes and very common
9,3x74R yes
5,6x57R unfortunately yes but not super common
5,6x52R yes 22 Savage
5,6x50R common, but maybe not exported kind of a 222 Rimmed kind of
6,5x57R very common
30 Blaser common
8,5x63R newer round, not super common but not impossible
30-06 oh yes, lots
308 yes, very popular now
270 rare
243 not sure rare, but not common
6x50R rare
6x63R rare
222 Super common
Then you will run into einstucklauf's Or insert barrels most in 22 based cartridges like the 5,6x52R, 22 Hornet and 222.
There will be others, and old calibers like the 9,3x72R and others that approximate it.
Current production is limited to Blaser, Krieghoff and Merkel. Sabatti made some for a while and another Italian company did too, but I don't think they are currently in production. I would not buy an Italian gun unless it was cheap.
New Drillings here in Germany are basically a $10,000 start.
Custom Drillings from like 30 or so makers on both sides of the Alps are still made. Suhl, Ulm, Ferlach, Innsbruck, and so on. I would say $20,000 would be a start. Maybe $17,000 for a super base gun if you are lucky. Most will be $35-75,000.
This is the German Egun website for Drillings.
https://www.egun.de/market/item.php?id=20068128. 3500 Euro Blaser D99 in 7x65R/20/20. This is a spectacular rifle for this price.
https://www.egun.de/market/item.php?id=20034174. This Bockdrilling is a dream.