The first thing you need to look at is a rangefinder. No gun of any cartridge will do you much good at 500 yards unless you have a rangefinder that can reliably range an animal or at least something you can depend on being near the animal (like a tree). The human eye is only reliable to +/- 150 yds or so at 500 yds, USELESS and you're slinging guesses without a rangefinder.

The second thing you need is better optics. You cannot reliable "hold over" for drops that far out. You need 1) a tactical-style scope with external adjustments, 2) A mil-dot scope, or 3) a BDC reticle, I recommend them in that order. I shoot a Nikon Tactical 4-16X 50mm scope on my 300WM. This fall I got the trip of a lifetime (so far!) to Montana for elk and muley and took my bull from 683 yards as I was not going to get another chance to get one closer.

The third thing will depend on what you hunt. Deer? A 270 might still be a 500 yard gun, I'd have to check the ballistics. I'd recommend a little more gun that far out and certainly if you intend anything bigger than deer.

The fourth thing is practice, and lots of it, which suggests the fifth thing, which is reloading equipment. I could not afford to shoot the quality ammo I shoot if I did not reload it for under $1/shell. Once you have a rangefinder, the biggest problem shooting long range is wind and while the computer will calculate rough drift values for you only a lot of experience shooting far and possible a wind meter can help you judge conditions and adjust your drift compensation.

Shooting long range is a complex process, and expensive to do it right, especially if you consider what I did:
Before hunt:
1) Put together long range rig - Remington Sendero, Nikon Tactical scope, Scope Level, Burris Signature rings with inserts to add addtional upward travel into the scope.
2) Learned to reload and got all the equipment
3) Carefully developed the fastest accurate load with 200gr Accubond in my rifle - 2945 fps
4) Gained 200+ rounds of experience at 100-400 yds
5) Two range sessions to 860 yards to verify drop chart, wind drift estimates,and group size (6inches)
6) Additional range time with .22 and muzzleloader at long ranges to practice wind drift compensation
7) Bought Bushnell 1500ARC rangefinder

During the shot:
1) Called in elk until he hung up and offered no stalk opportunity without being winded.
2) Several range readings to be confident in range - 683 yards
3) Set up gun and leveled Harris bipod legs
4) Adjusted magnification and side focus to eliminate parralax error
5) Consulted drop chart, dialed in appropriate drop
6) Estimated wind through valley in front of me, consulted chart to dial in wind
7) Got all set, verified spotter was ready to call my hits
8) Verified gun was level with scope level, tightened in and fired first shot
9) Spotter called he couldn't see it, animal did not react (he was well hit)
10) Repeated firing sequence, fired again. Spotter couldn't see it, animal didn't react (well hit again withing 6inches of first hit)
11) Double-checked all calculations
12) Fired third shot; spotter called he heard the hit, animal turned 180 degrees at the shot
13) Fired fourth shot; spotter called miss right at his nose. Realized wind drift was a little more than estimated (first shots had just missed lungs through liver), so pulled the crosshairs further over and fired fifth shot. Heard shot impact (boilerroom shot perfect), animal reacted slightly, walked behind tree where he soon collapsed.
14) Waited an hour before approaching animal as you can't see what happens that well from that far away!!

Long range rifle hunting is a complex game and a lot more than just getting a gun and scope that will get bullets out there! Study up, read longrangehunting.com.