My best friend has a 30 carbine and I helped him load up about 200 rounds for it. We used 15.0 grains of H110 with the 100 grain JRNs and 14.4 grains of Lil Gun with the same bullet. No problesm with either load and they seemed to be accurate loads. Start low and build up as usual and you should quickly find a load that works for you.
You are correct in your observation of the loads being similar for a .357 mag! The loads for the .357 are about the same. The 30 carbine is basically a pistol type load. Ruger put out the Black Hawk in 30 carbine at one time. I saw a used one recently for sale at the local Cabelas. I use Papa John's pet load of 16.2 grains of Lil Gun for my .357 158 grain jacketed bullet loads. Very accurate! I have used loads from 15.0 grains to 16.5 grains of H110 for the 158 jacket .357 rounds as well.
The 30 carbine is a real kick to shoot and you are going to have a lot of fun with it. Enjoy!