Realistically, taking a 600+ yard shot is really hard to do. You need a solid base, bi-pod minimum. Not many places you can use a bi-pod in the field, unless you are lucky.

And even then there are a lot of variables, ambient temperature, uphill or downhill, shooting through air layers, rifle and shooter capabilities, figuring in bullet drop, accurate range calculations. People forget about ambient temperatures, a twenty degree difference in the temperature from your zero temperature can cause 1/2-1 MOA difference.

Most rifles are doing well to get 1 1/2 minute of angle under ideal conditions. That is nine inches +/- at 600 yards. Without any other variable. The chance of throwing one out of the kill zone is pretty darned high.

The only way to know for sure is to practice at your selected ranges, and practice under different weather conditions and keep a book. Pick your ideal range where you can put every round into an eight inch circle, this allows for some of the variables and helps prevent those "Oh chit" moments.

Just a side note. the angle of the butt stock to the barrel often changes from one model of rifle to another. Many of those notes you took and put in your shooting book, you can forget when you change rifles. The reason being the angle of the butt stock often transfers some of the recoil into a vertical motion, which begins before the bullet leaves the barrel. Different bullet weights and powder burn rates change from one ammo manufacturer to another and even different lots of the same ammo from the same manufacturer.

I have no great confidence of making, sure thing, one shot kills at 600 yards.

My kill zone is 8 inches on most game, I'll fudge a little on varmints. My personal limit is around 350 Yards in the field.

I took a shot at a Fox, 25% slope down hill, where I was shooting from it was 75 degrees F where the Fox was there was patches of snow on the ground and it was likely 40 degrees F, air layers. The range was 400 yards. I put it right through the heart. That Fox wasn't luck, but maybe I could repeat that shot and maybe I couldn't? I'd passed on a trophy Buck and hour before, at the same range and on level ground, I wasn't absolutely sure it would be a kill shot.

IMO pushing the envelope isn't something you do with game animals, it's something you save for varmints.