oof...bunch of questions. I'll answer using the build I have, with the caveat that mine is a Savage. I am having a 26 inch 1:11 heavy sporter Benchmark barrel on it, because, for that i shoot, I like it best. For scope, since you said, 500 yards there are a lot of good options, Nikon Monarch, and maybe even Buckmasters, the Vortex Viper line is very popular, Sightron III is also a good decision. Weaver makes a bunch of good scopes. For more expensive there is Nightforce, S&B, Zeiss, and Swarovski.
a little more information would be helpful for giving you advice.
as far as bullets, I've used 178 Hornadys, but recently decided to dial back the weight and up the velocity, so when i get my rifle back, I'll be trying out 155 Berger VLD, which, if I can get a solid load from them, will be used for hunting and mid range (600 yard) F-Class shooting. I use Varget for loading my own rounds.
That's about all I got, I'm a newbie, and others will be along with more knowledge.