Re: DPMS Panther LR .308
I know I'm new to this forum, but I'm not new to shooting. I feel fairly confident in saying that if you aren't aware of some basic loads for a caliber as common as .308, you should probably not be worrying about shooting at 500 yards, definitely not 1000. I would stick to making sure you can get good groups at 100 or less first. Learn good trigger control and natural point of aim. Also practice some dry firing drills with snap caps to see just how bad your trigger flinch really is.
That said, a CLASSIC .308 round for 300 yards or less is a 168 grain Sierra or similar match bullet with a good powder, such as Varget. If you insist on shooting 500 yards and beyond, consider a 175 grain. People have also been having good luck with 155 grain bullets.
As I'm sure you're gathering from the responses to your post, responsible gun owners don't like it when people walk in and act like cowboys. People who act irresponsible give a bad name to the thousands of responsible gun owners out there. Not saying this is you, but just be careful what you say and how you say it, particularly in public.