Have to agree with IXLR8. The JRC is a great idea, but too pricey for what it is and what it does. For that price you could just as soon build yourself a decent 9mm AR. One of our site sponsors sells those Quarter Circle 10 lowers that accept Glock mags. You'd need a Glock compatible bolt and a 9mm upper. I think there's a company called LDR that sells a Glock mag AR as well.
For a pistol caliber carbine, there are a lot better options out there than JRC. Especially once you figure in the price of the JRC. Heck, you can even get an M1 Carbine copy that shoots 9mm.
Lone wolf sells a 9mm glock lower.