While I was messing around with snap caps I kept experimenting to see how I could pull low/left and I believe it's due to lack of forward palm support and too much finger pressure. In all of my shooting, with every gun I've shot, I've practiced the following method and it's always worked for me. Try gripping the pistol by the front of the grip, with only your three lower fingers and knuckle part of the palm, then wrap your hand on around and depress the grip safety on the back of the grip and position your thumb forward. If I don't press lightly on the thumb depression I tend to hit right slightly. Make sure the web of your hand is firmly pressed into the grip safety so that it will not move under recoil, this will reduce felt recoil slightly as there's less slack. Make sure the heel of your hand is firm too so that you don't pull downward with your lower three fingers and web of your hand. This may seem slow, but it doesn't have to be so methodical, as long as you get a good grp all the way around, leaving no gaps. From holster, I typically jam my hand into the grip safety, lock my three fingers into position, pull, position thumb, and then place my finger on the trigger once I'm on target. A gap in the forward area of the palm will make you turn the pistol slightly to the left if you're a righty, and slightly right if you're a lefty. A good grip from all directions with equal pressure is necessary, as a slight imbalance will cause it to move off center. Another way about fixing this is to only grip by the front and back of the grip, putting no palm pressure or finger pressure on the grip. I find this difficult and uncontrollable, but a few shooters in my area, particularly 1911 shooters, have had great success. See if either of these grips work for you.