Which AR10 caliber

7mm-08
308
6.5 Creedmoor

Going to build one for hunting and shooting steel at long range. What are the pros and cons of these calibers?

7mm-08

Borrows some speed and BC from the 6.5mm, borrows some energy delivery from the .308.

7mm-08 and 7mm-08 Ackley Impoved are the best at everything. There, I said it. (Yes I have one of each)

I say 7mm-08 as well. Mine is a bolt action but it has never let me down in 35+ years of hunting with it.

6.5 creed. Plenty of factory ammo. I have a 16” and 22” uppers. Both shoot 1/2 MOA. I used a Wilson combat Ranger 16” barrel on my last build. It loves factory ammo

Not sure what you consider long range but it helps to be a reloader for long range shooting. You can load it more consistently than factory ammo and tailor it to your gun. Also the 160gr range of bullets and some 150gr bullets will have higher BC bullets than most factory ammo which is mostly 140gr.

Info off the ammo in the 16” barrel

I do reload, so I can get better/consistent results over factory ammo. I define long range shooting as 1,000-1,300 yards. I can also shoot hogs at one of my setups at 500-700 yards.

I still pick 7mm. I have lots of love for 6.5 Creedmoor, and .308, and own all of them. If I had to pick only one to use for lomg range target, and hog hunting, 7mm hands down.

My choice was .308 for the AR platform simply because I do not reload, but I do stack ammo very tall and deep for various reasons.

The .308 fills the slot of a "good all purpose lower cost round" for the AR with decent performance for my needs. The wide range of factory ammo (and 7.62x51 for bulk) makes it universal for me.

I suspect that if I tried the 6.5, I would like it - but I have not.

Marc

I agree for the reasons you pointed out. Yes, you would like shooting the 6.5 CM.

I would add one or both uppers after starting with the 308.

For what you’re intending 7mm-08
I own a gas gun 6.5 creed for hunting.
My long range precision gun (bolt) is a .308.
7mm-08 has best of both these calibers.

Never under estimate the power of cheap ammo. Not everyone has the time, knowledge or inclination to precision reloading every rifle. For this type of rifle and my personal needs, the choice is 308 by a wide margin. But then again, I might ever only own one large frame ar, so the answer is clear for me

I like the 308 because it’s $17 a box

I would not be selecting an AR-10 if this was the goal. A 7-08 would be a great choice. But for a 7-08 to fit and feed out of an AR magazine means the high BC bullets desired for long range will have to be seated deep in the case. This will reduce your case capacity (i.e. less velocity), and the bullet will have a long jump to the rifling.

On the other hand, the 6.5 CM round you can seat the bullet out long and still be close to the lands while feeding out of an AR mag just fine. And, the 6.5mm bullets have a high BC and are lighter and can be pushed faster than a 308 or 7-08. For this reason, I would select an AR in 6.5 CM, if 1K+ yards was the goal.

The 308 in an AR will be running out of gas around 900-1000 yards, and may not make it much more past that. It will have much more drop and wind drift than the other rounds. I absolutely love my AR-10 in 308, but it is not a 1K+ rifle.

Come spend a day on the range with me, and I'll show you exactly what cheap ammo really means.

For example, look at Tye's post from above. His reloads have a 20 fps ES (extreme spread) and is loaded with a match grade temp stable powder, H4350. The factory ammo pictures show an extreme spread of 41 fps on only 3 shots for the 129 SST and a 52 fps extreme spread for the 120 GMX on 3 shots. And this factory ammo is loaded with ball powders powders that are temp sensitive. What do you think the ES would be with more shots on the factory ammo!!??

The high 40 and 50 + ES is from a varying powder charge inside the case of factory ammo. This high variation in powder charge will easily cause fliers and many rounds will take you in and out of the main group of factory ammo. When you are only shooting at 100 yards, a high ES doesn't show itself as much. But at longer ranges, it will show on the target in vertical stringing. Meaning, the bullet will impact high or low, simply based on a variation in velocity. Plus the variation in "sweet spot" taking you in and out of the main group. I've seen it many, many times.

I actually prefer value than the word cheap. I think your reloaded 308 was cheap, meaning value, but it cost than some core lokt I found.
And final response, there are some instances where good ammo is just as good as bad ammo. Namely, just blasty fun times.

I'm a big believer that both cheaper and pricier ammo have a space in my ammo inventory.

After reading the article on the “ladder” from the 6.5 guys, I figured to give it a try. I loaded from 39-41 grains for the 143 ELDX and 140 ELDM. Once done, I selected the node and loaded up 5 rounds and give it a try at 400 yards shooting prone with bipod and bags.


I noticed there was very little vertical dispersion and only wind drift.(exactly what I was looking for)


I also was testing some of my hand loads and the Hornady Precision Hunter ammo. My hand loads had a SD of 4.8 (best node) vs the factory ammo of 13.3. Shooting groups at 100 yards doesn’t tell you much. If you are wanting a good long range ammo, you need to test it at distance. I try to shoot 5 round groups and not 3.

BIAS!

Lol, just kidding Jason. I like the Ackley too. And ultimately I would suggest anything but .308.

What barrel length in 7mm-08 or 6.5 Creedmoor?

Which is more important to you, short and maneuverable or, longer making more muzzle velocity? Suppressor or no suppressor?

I shoot suppressed on most of my rifles. I was thinking 20” barrel might be a good compromise. Not sure if a 20” barrel would get me to 1,000 in these calendars. Thoughts?

20" + suppressor certainly will get you to 1k in either 6.5mm or 7mm.

1000 yard calculation using 143 ELDX in 16” creed