Yup, the montana bill withstood the surpreme court. It basically relied on the premise that started the Civil War, and the same premise that has allowed California (among other states) to allow the use of marijuana. To abide by the US constitution, the laws of the states are not allowed to further restrict the rights of citizens, only to grant them EXTENDED rights. So the states can legally pass laws, if they follow due procedure, that would contradict the federal authority. So while possession of controlled substances, or Class III weapons might be regulated by the BATFE, it is the right of individual states to waive such requirements for it's citizenship.

Personally, I've never been a fan of using sub-sonic centerfire ammo because the power factor and range are so poor. The alternative is to use a bigger bullet, but the bigger the bore, the less effective the suppression.

All that said, check your state regs. Hunting with Class III's in many states is prohibited, even if it IS just a suppressor.

That said, back in college, I bought a pre-ban suppressor ($200 tax stamp, $1600 for the suppressor) and threaded the muzzle of a Win 94 Trapper lever action. With .357mags, it was pretty quiet, but still made a "crack", with .38spcls, it was nearly silent. Somewhere between an air rifle and a .22lr fired underwater. It was pretty nice for hunting hogs and coyotes at night down in TX without waking up the neighbors on the next 40.