Well, those jacketed rounds certainly do go against the conventional wisdom. Having said that, there ARE factory subsonic rifle loads with FMJ out there, I suppose (.300 whisper and subsonic 9mm for SMGs come to mind, but the SMG barrels are usually quite short). Having said that, you have to be DAMN careful. I wouldn't do it. No need to. At subsonic velocities in a long barrel, there is no real advantage to using a jacketed bullet. A properly constructed lead bullet will get you basically the same performance, and probably better expansion, since most jacketed rifle bullets are not meant to expand at all at those velocities.
