I am an old shooter but a new deer hunter.

I recommend you don't conclude anything until at least firing a 3-shot group. Adjusting the scope for each shot will result in wandering all over the target without learning much.

If you are shooting at a target that is at least 100 yards away, I would just remind you to take some wind into account as well. Crosswinds will tend to affect lighter bullets more than heavier ones.

Also, be sure you are keeping both eyes open. If you are right handed and right eye dominant, this should be fairly easy to do with a bit of practice. If not, you may need to try an eyepatch, at least at the firing range. When you close the non-shooting eye, inevitably you will squint a bit with the other. During an extended session at the range, your vision in the shooting eye will tend to get blurry from keeping the other eye closed.

I wouldn't worry THAT much about the barrel heating up. You would certainly notice it shooting at the National Matches on the 1,000 yard targets, but not too much shooting through 20 rounds in an hour or two.

Then again, I could be wrong...