Softpoint,
Since you are using your first joint, I would say that is likely not a problem. As long as you don't have too much finger on your trigger, that should eliminate pulling the gun down too much. Another exercise you could do to help cure your flinching is to practice dry firing in your living room, or elsewhere, with a certain design on the wall or an imaginary target (if this is agreeable to you.) But try and get some practice in by just pulling the trigger and getting used to the feel. I must say this, just to make sure:
Make sure it is empty! I always stress that when doing this!! Also never use a gun with a loaded mag in it while pulling the trigger; it is just another liability. Snap caps come in handy here when you don't want the pin to fall on an empty chamber.
When you see what your sights do without really shooting the gun, it will help you see if you need more practice. Your sights should move enough during practice that you will see the need if it is there. I usually do that myself before a pistol shoot (practical pistol, not genuine competition) to help me with my sight picture, drawing, and trigger control. All you have to do is just pull the trigger back, not thinking of either the gun going off or the sear releasing, but concentrating only on your target and your sights until it goes off. If you concentrate on the target and sight alignment more than on the gun going off, it will help considerably to eliminate any flinching. They say accurate shooting is more mental than physical; I went through the same tough road, so don't feel bad about it. In fact, I do regress from time to time, so I'm not really out of it yet. :shock:
I think the heavier bullet/higher point of impact has to do with more muzzle jump because of the recoil. I can understand the principle better from my experience yesterday between shooting off a bench, and shooting off hand. I was sighting in my 45 ACP at 25 yds. with a new adjustable sight I had put on. While benched, it worked amazingly well; I could keep five shots within a 5" circle (this is without accurate load development; just a simple work-up) dead center. Once I shot it offhand, it was shooting at least a foot higher! This was simply because of the effects of recoil. Off the bench it didn't jump nearly as high, whereas shooting offhand, the gun was free enough to jump enough before the bullet left the barrel. That is all it takes to move the point of impact. There was an immense difference, and I think that is the point PaulS was making.
These are some tips I use that helped me with my shooting habits and form. I hope this helps you out further, and if any more questions remain, feel free to ask them.
-Patriot