field989,
a 30-'06 improved, 35 Whelen or a number of other long cartidges can do what you ask and will be cheeper to build than the long magnums. You might be able to build a good 500 yard shooter for about $1500. Get a used long action, (I would recommend Remington 700 but there are others) have it and the lugs trued and bolt face squared. Select a smith that can do the work and talk with him each step of the way. He has to know what you want in order to provide you a gun that can do it. SEe what he thinks about your budget and the gun you want. You may not get a real nice stock for that kind of money but if it is bedded properly you can get it to shoot. You may need to add another $500 for a decent scope but it might be a necessity if you have old eyes like mine. Good luck with your project.
Paul