Your loads are fine, elk aren't armor plated. So don't screw around trying to make heavier bullets work.
BUT, AND THIS IS IMPORTANT!!!!! Don't shoot 500yds at an Elk. Why? Two reasons:
- You're supposed to be "hunting", not shooting. So hunt - get closer. If you can't get within 300yds of an Elk then you truly suck and should take up a different hobby.
- Giving a Elk a 500yd head start is a downright dumb idea. Elk don't just fall over because you used a cartridge that impresses forum-dwellers. Elk usually are going to run a ways (unless you CNS them or pop the heart). It's a tough job to start tracking in falling light after you finally hike over to where the Elk was. I've talked to too many nimrods who say stuff like "I found blood and hair but I'm sure he survived" - don't be one of them.
Sorry if this comes off heavy-handed, but I've had too many guys tell me their lost Elk sob stories and I know there seems to be a growing trend for sniper wannabes to get bragging rights for the longest shot. My Elk go in the freezer - every time, either by bow or 45-70.