Hunting & Fishing Got drawn for elk! Help me choose a caliber!

I'm not going to pass up a close up opportunity if it presents itself, but part of the fun and challenge of the hunt is engaging targets at distance. Yes, I'll take am elk at 50 yards, but I want a cartridge that'll serve an ethical kill at 500+. That's what I'm concerned with. I'm 90% 1.5 moa cold bore accurate to 550 yards in most weather conditions(set aside varying gale force blowing dust winds). I'm no sniper, but I think I can do my part. So I just want a cartridge that will do it's part if I can send that bullet to my harvest' vitals. From posters here, it sounds like the right bullet behind my 7 saum is more than up to the task.
Now I just need to know what unit I got , in AZ, it could be the difference between needing a muzzleloader or a cannon.

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Good to know. My buddies got unit one first archery bull, so they got their hands full and money tied up in their own hunt. But I have a co-worker friend that knows exactly where to go in unit 27 and I'm hoping he can get some time off work to help me out, because I WANT this hunt to be successful. Given the area, I'm fairly certain I'll be hard pressed to have opportunities beyond 400+ yards so it looks like I good done practicing to do with the 7 saum...

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