GF,
There was some data re this with my Kel-Tec Sub-9. There have also been several articles out lately about the Kel-tec and Ruger carbines, some of which listed velocities. I believe the most velocity increase was from a 90-grain Corbon. I seem to recall it was doing 1700 fps or so from the 16-inch barrel. The type of powder used is going to make a difference. I'll see if I can get more info for you later, or you can write me in a week or so (I'm out of town currently) for more information.