For precise handgun shooting, I like to use a sandbag about half full, laid in a "V" between two supports. Don't let any parts of the pistol touch the bag, just use it as a cradle for your hands. Consistent hand placement is critical, and varying your grip can easily cause the vertical dispersion you've experienced. Take notice how far up the rear of the grip you place the web of your hand everytime you lay in the pistol. One thing that a lot of shooters don't think of is to blacken your sights...it makes a huge difference. Just take a butane lighter with the (unloaded) pistol upside down,and run the very tip of the flame over the front and rear sights till you have a nice dark sooty coating. Then it's all about a clean break on the trigger and FOCUS on the front sight. The front sight must be crystal clear and the black bull of the target will appear fuzzy gray. If your eyes are young and sharp, you're good to go. Once you hit you mid 40's, 50' etc., you may not be able to focus as well on the front sight. There are apertures made that attach to your shooting glasses to correct for this.If you're cheap, just place a piece of black electrical tape on your lens with a hole punched in it a little smaller than a BB. My 50+eyes suck, but with a little care, I can still hit a hubcap at 200 yds 5 times out of 6 with my .44mag!
