I am thinking about getting a new AR and I would like to get something other than 5.56 but I can't decide what . I've been looking at the 7.62x39 , 6.8spc and the 6.5 Grendel. Any suggestions?

I've got one in .458 Socom and love it!

Buy me one and I'll evaluate it for you

Get Cole Blackmon to build you a 7.62x39, since you mentioned that calibre. If I owned an evil black rifle with an obscene amount of ammo, that would be my choice.

Hmmmm before the flood carried off mine, I owned a 450 bushmaster, 6.8 and a 6.5. Kinda hard to choice because I liked all 3 of them. The 450s accuracy was impressive, I was getting inch groups at 100 yards out of a 16" carbine barrel...

They chamber.260s in Ars too.

If you ever get down to Mobile and you've got a Marlin 30/30 plus some boot I'll trade you a complete PSA 6.8 SPC II mid length upper, two mags and ammo. PM me if interested.

I have 6.5 grendel and 300 blackout AR's. I really like both of them. The grendel is better suited for a longer barrel (20"-24") and thus a longer rifle, but has more range, better ballistics than the 300blk. However my 300 blackout I use a 8.5" barrel in an ar pistol so it is very light and compact and I fell really confident with it out to 150-175 yds on animals, 200-250 yds on targets.
Ammo for both is fairly common. I think there is a lot better variety of ammo available for the 300 blackout right now and you can buy it at walmart. If you reload blackout there is an endless combination of loads. If you go suppressed, the blackout really shines.

Now my 6.5 is great too. Really flat shooting and great ballistics. It has almost no recoil. At longer ranges it carries 308 type energy. I have a JSE upper with a 20" stainless bull barrel and it is VERY accurate. It is a little on the heavy side though.

If you plan on hunting over 200 yds I guess 6.5 grendel would be better for you. If under 200 yds consider the Blackout.

I have to agree with ValleyDawg,
While you may as well have a 5.56 upper, it really is about the least effective round for deer or hogs out of an AR. I mean no disrespect to those that hunt with it successfully, I base my opinion on what I've seen in the field. The 300 blk is about apples to apples with 7.62x39 ballistically without the issues of feeding in an AR15. As stated, either 300blk or x39 are good on game out to around 250yrd
If you have the right bullet and you can get that performance out of a very short weapon and it only improves a little out to 16" barrel.
I just built my 6.5grendel at the end of last season and have not killed with it yet. However, my 22" barrel build has been printing .4-.6" groups for me at 100 yrds and, running my numbers it nearly matches my 30-06 out to around 550yrd. I wouldn't hesitate to take a shot at game out to at least 400 with the Grendel. I can't tell you about the other flavors as I don't have much practical experience with them.

I would skip all that and go straight to an AR10 in 308.

I would only go 7.62 or 6.8 if I was adding another upper to an AR15 that I already owned.

Thanks for your input guys