Brent,
You need to do more research on the science of bullet stability. I would suggest Bryan Litz's book as a starter.
One thing is certain: The two groups do not provide enough information. If we just eliminate either the left or right shot in the bottom group, the other three shots would be about as relatively accurate as the top group at 125.
The drop is more of a puzzler. Even a very bad chronograph reading (and I have seen cheap chronographs give readings as much as 10% off over the years) wouldn't explain that much drop.
The scope may also be the culprit. In fact unless a scope has really been proven on another rifle, I tend to suspect the scope first in most problems with smokeless rifles.
On Savage 99's the forend would be second on the list.
