When you say "all over the bullseye" with your friends gun, I have to assume you mean you were on target? That said, the P11 is a true double action pistol, and as such has a very heavy trigger pull, much like double action revolver. Many shooters new to this pistol shoot low until they have learned and adjusted to the trigger pull (which is very different from most semi-auto pistols). Also, when you say you shot from sandbags, were you actually resting the pistol barrel/slide on the bags, or like many, just resting your hands. If it was your hands on the bag, with the gun not actually touching (except perhaps the grip bottom), then it is very easy to pull off target while trying to pull that long, heavy trigger through. So, no real surprise you would shoot low. Perhaps have a more experienced shooter try the pistol, or if that is not possible, then use a rest to actually rest the pistol slide/barrel on to help in keeping the sights on target while pulling the trigger. Then, if still shooting low, you can carefully file down the front sight a bit to raise point of impact (do this a very little at time), or like Txcajun suggests, even easier is to get a rear sight shim kit from Kel Tec to raise the rear sight as needed.