By small caliber out to 500 I'm assuming 243 or 308 type stuff. But if you want to take game at a 1K. You need to answer some question for yourself first. The answer to alot of these questions depends on how deep your pockets are.
1) How much are you willing to spend up front and in the long term? To accomplish what you are after you need a rifle w/good scope, rangefinder, spotting scope, wind meter (or some way to read the wind). These are up front investments. The the other investment is in reloading gear and components. You will run through plenty of ammo practicing and working up ballistics tables, thus you need to be ready to buy plenty of powder, bullets, primers, etc....
2) How much weight are you willing to carry? Many of the guys that hunt at those distances carry around 15+lbs rifles. Generally speaking the rifles in the larger 338 and 375 calibers have 28+ inch barrels and are rather heavy.
3)How recoil sensitive are you? With a good brake the recoil of these big rounds can be tamed. These are rounds that carry heavy bullets and lots of powder. Thus they can thump.
4)There are lots of calibers that will do what you after. The most economical will be the commercially available 7mm and 300 magnums (WSM, Rem Mags, Ultra Mags, Weatherbys, etc...) Now if you really want to go for some of the bigger more expensive stuff you can but it gets pricey. But the 338s and 375 excel at dumping large amounts of energy into their targets at long range.
The point of all this is that we need more information in order to answer your question. Try to help us fill in the blanks so we can give you an educated response.