The speed is still way too high without some kind of massive compensator (lots more weight, muzzle break, etc.) Considering the pistol round normally travels below 1,000 fps, I don't see how you're getting it to 3,000 fps, mass driver included.
Also, if this is going to be DR 3, you need more than just 10 mm bullets. You need armor penetrating rounds that are made of uranium, they need to be spitzer-shaped. And you still need a bloody stock to firing this thing anywhere near accurate — the perceived recoil right now, based on caliber and muzzle velocity alone, is extreme to utterly uncontrollable. "High" is inaccurate.
DR 4 is too much. There's no way, not even when the round is "mass driven," that this thing reaches DR 4. The LASR reaches DR 4, and it fires its rounds much, much faster, with a heavier, more aerodynamic bullet, and with better construction.
This weapon seems more about the cool factor than accuracy. We do approve weapons like that on occasion, but many times that's because we don't catch the things wrong with them. I know there are things wrong with this.