So, i'm looking at buying/building an AR platform rifle. I am sure I don't want a .223 but I cant decide if I'd rather have a 5.56 or 6.5 Creedmore. Pro's v. Con's? Ammo expense & availability issues? The idea for the rifle, is open iron sight or red dot to easily index targets at 500 yards & in. I already have a long banger built up. Thanks in advance.

If you don't want a .223, then I don't believe you want a 5.56 either.

223 and 556 are essentially the same cartridge. 6.5CM would be a LR308 pattern rifle not a AR15 pattern. The LR308 is big brother to the AR15. Two totally different animals. If you're wanting open sights or red dot I'd say go with 556. Kind of a waste of 6.5CM not to scope it and reach out.

For that distance AR10 for the creedmoor or AR15 in 6.5 Grendel

open sights 5.56/.223
the cost factor between the AR15/LR308,AR10 is about $1000.00

You know you don’t want a 223 but you want a 556

He prefers the metric system.

556 is externally the same as 223, do some research on that. I say get the 556, it can go to 500 like you want and ammo is everywhere. Like KRoyal said, the 6.5 is an AR10. It will cost you more and for what you are shooting, the ammo cost doesn't justify unless you want to hunt, that would change my opinion.

As others have said, if you don't want 223, then you also don't want 5.56. So I'm assuming you want something bigger.

Having said that, I would heavily consider a 308. The advantages of 6.5 are mostly related to precision type work and I'd prefer the higher bullet weight of a 308 to the ballistic advantages of the 6.5 in an entry-level gas gun. But that's JMHO

I should have been a little more clear in my posting. I know that the .223 & .556 are essentially the same round. My understanding is that you can shoot a .223 through a 5.56 but not the other way around. I figured that being the case,(if that is true) then to go to the 5.56 would increase the availability of ammunition that you can use to shoot with. Maybe I'm wrong here

That is correct and most hunting ammo comes in 223 a lot of the 556 is the military ammo and for the most part FMJ. As long as your barrel is stamped 556 you can shoot both.

Kmon has made a good suggestion here. If you have not considered the 6.5 Grendel, you should take a look at it.

In an AR-10 platform, I'd look at these two:
DPMS Recon GII in .308, ~$1200
Savage MSR-10, either .308 or 6.5 Creedmoor, ~$1100

If you're going AR-15, I'd look at either the .224 Valkyrie or the 6.5 Grendel if you're hunting deer or hogs. If all you're doing is punching paper, varmints, or you really like mag dumps, go 5.56.

I'll speak the unspoken. Thought about a 6.8 SPC?

^^This.

6.5 Creedmoor, .308, 6.5 Grendel all right at home at 500 yards.

You can get a .223 to do it, but it's probably going to require a hand load of 75+ gr bullets, and it would be better to have a 20" barrel.

Hey JG, do you have a Grendel yet? I can't recall you having mentioned it.

I do not.

I've got a 16" 5.56mm and a 16" LR-308. The Grendel would fit in the middle, and I just don't see the need. I get free .223/5.56 and .308 brass monthly, I see no reason to go to an upper that runs on brass that I have to buy, and that takes advantages from both sides of it. But, if I had to run one, and only one AR platform, there is zero doubt in my mind it would be a 6.5 Grendel.

I've had a few out for the class, and spotted them to 800 yards. And they repeatedly hit the far targets at will. And the ones I watched shoot during the Hunter's Rifle Challenge were salty!

What? I got my AR-10 6.5 CM for a grand so are you saying they're giving away AR15s?

No it’s not.

Agree, for hunting purposes anyway.

Have you considered the weight difference between the 10 and 15?

won't be an issue with the savage msr hunter

I went to talk with the guys at Faith Armory, in Waxahachie today, and I cant say enough about how helpful they were. They spend a solid 45 minutes answering questions and explaining different aspects of the rifles. I ended up going with a Ruger 556 MPR, with an 18 inch barrel and a free floating rail. Magpul furniture and the "elite" 452 trigger @ 4.5lbs. I feel pretty good with the decision. I may upgrade to a stainless bolt and I still havent decided on optics, RedDot or scope but I appreciate all of thr input from forum members. Good stuff

500 yards means scope, and not just any scope.

Yeah, that is what I gathered from our conversation today. It sounds like i'm going to have to put back or revise my expectations on yardage