Sorry to be a wet blanket, but I just don't get that excited about wildcats based on usually already rare parent cases. Take the 375 JDJ which I think can be reasonably said to be the most successful of the JDJs. It's based on the 444 Marlin, which isn't even a common case, and is trouble enough to get your hands on, let alone potentially destroy in the conversion process.

Then start asking yourself WHY? How do any of the JDJ cartridges do something better than an already available cartridge? For example, is the 375 JDJ really an improvement over its parent, the 444 Marlin? Both cartridges are way overkill for deer, so lets focus on Elk. 444 Marlin, under 100 yards, offers better KO values. And beyond that, I really begin to doubt the wisdom of using a handgun. And 430 diameter has a much wider bullet selection than 375, too. To me a 375 JDJ makes MORE sense in a longer barreled rifle, like a re-barelled Marlin formerly in 444 than anything else.

The same goes for small bores it seems. Is there a small-bore JDJ cartridge that can do something the 7-30 Waters or 223 Rem can't?

I have owned several bizarre (44 Swiss), obsolescent (7.62x38R), and wildcat chambered firearms in my life, but now I've whittled it down to only one: 357 Herrett, based of the 30-30, and nearly perfect for whitetails. Common parent case, wide bullet selection (357/358, both pistol and rifle bullets), and no brutal recoil. I've fired a contender with a 375 JDJ and a X-Frame S&W in 500. No thanks!

But for those that like the JDJs, keep on enjoying them, anything that makes Contenders popular I support.