My two longest kills are with a 300wm shooting 180gr Partitions. One white tail buck at 430 yards and one Mulie doe at 505 yards. Both measured with laser rangefinder before the shot, calculations made and accounted for, taken from prone using my pack as my front rest. 500 yards is not rocket science, but it does take practice and a good understanding of ballistics(exterior and terminal) as well as wind reading ability. If you have the skill, the proper equipment, and the right conditions a 500 yard shot is nothing.
If the conditions were perfect I would be comfortable out to 700. If they are horrible I limit myself to 300-ish. Know your limits and stay within them.