I've always been a big fan of the .30 carbine, too. Some people, starting with the US Gov't have always placed overly high expectations on it, so it's been a disappointment to many. If one thinks of it as a .22 magnum on steroids it's far more likely to satisfy the end user. The Israeli police have done some interesting things with it, including the special purpose
Hezi SM1 which uses the .30 carbine round and M1 magazines...