Clodbuster,
What you probably don't need is an adjustable objective scope.
Unless you are going to have time to play with bringing that into focus,
I would stick with the fixed objectives, in the 3x9 to 3x10 range.
Things are going to look tiny at 500 yards, but you will be able to
get on the target, faster, at any range, with a fixed objective scope.
All of my varmint/target rifles have adjustable objective scopes,
for small targets, at extreme ranges, and there I usually have time
to adjust the objective. None of my game, or predator, rifles have
adjustable objective scopes on them. Around here Wiley doesn't
give you more than a few seconds, to get on target, and get a good
trigger pull, unless it is early in the year, and there are a lot of stupid
pups around.
So, if this were my decision, I would be looking for a good 3x9.
Actually if this were my decision, and I had the cash, I would
buy a Savage bolt gun, in something like a .25-06, or a 7mm
mag, a good bipod, and a nice clear 3x10scope, and get to a 600 yard
range, to tune the rig for long range. "up to 500 yards or more", is a
pretty long poke for a lever gun. I suspect you have a lot of
confidence in that Savage 99.
Squeeze