Regarding practice, or rather, testing, if you really want to be a long range hunter...

Remember, the only groups that matter are one-shot groups.

Practice all you like and please do, but to really find out whether you can kill game consistently without wounding at long range, try this little "game" for a test.

First, always use a critter-shaped target. No bullseye or other scope- or sights-friendly targets. Shoot in all weather. Do not puss out and only go to the range on still, calm, windless days unless you only hunt on such days.

Now, every time you go to the range and BEFORE YOU DO ANY SHOOTING, set your target at long range, go back to the firing line. Gather several fellows around you to watch if any are present and fire one shot. It is best if you can do about a 1/4 mile sprint to get your heart rate and breathing up first. All in the attempt to duplicate field conditions.

Now, go check that one shot. That's it. That's the one that matters. That shot should be comfortably in the kill-zone of the animal target you are using.

When you can do this consistently without groups or "fouling shots" being fired, you are getting there.