The 5.7mm Johnson is the .30 Carbine case necked down to .22 cal. From the data I have you should get around 2,850 with a 40 gn. bullet and 2,700 fps with a 50 gn. bullet. You would have to make your own brass. This is done by necking down .30 carbine brass. To do this you would need a set of form dies and have to annel the cases. If your not into wildcatting this would not be a real good choice to start with, but it`s not impossible eather.