I have no idea what the design specs were on the AR-10, but I do know that the basic system design depends on a specific weight projectile traveling at a specific velocity in order to make the whole thing function properly.
I have no proof, but I suspect the majority of the reliability problems with the AR10 series is that folks are putting lots of different bullet weights at lots of different velocities through them and expecting reliable functioning. That's just not going to happen.
The other major drawback I see to the AR10 is that mags and spare parts are scarcer and more expensive than hens teeth.
You said you wanted a decent battle rifle in your original post. Now the AR10 is a well built rifle, but I don't think it's quite graduated to the status of a 'battle rifle' if you know what I mean.
The FN and the M1A are both field tested and proven designs that have functioned all over the world under the most extreme conditions. Both of them are still killing the enemies of freedom. It's hard to argue with that.
If you're really looking for a battle rifle, I'd confine my search to the above types and scratch the AR10 types off my list. Yea, they're cool but they just haven't 'seen the elephant'.
As I said before, this is just my opinion and your mileage may vary.
L
It seems that in the past 78 years I have fired them all.H K 91 & FN-FAL are jewels but so is the M1A1,M-14 some AR-15 & 10's will do in a crunch.
Anyway,it depends on how you define "battle".
There really isn't a battle rifle.
In WW 1 Sgt,York killed 32 Germans & captured 136 up close & personal with a Sprigfield 1903 5 shot bolt action 30.06 rifle.
Me,I'll stick with my M-1 in .06 and .45 1911 A-1 Colt.
I have a 1938 Swedish Mauser in 6.5 for talking long distance.
And my grand paps trusty Winchester M-97 12 guage pump with double ought buck.
Coming in on the FAL side of the argument, I'd also point out that the field-adjustable gas system can be a life-saver if you're really running through the ammo. When there's no time to clean a battle-fouled rifle, the adjustable gas system will allow you to put rounds down range for a while longer.
General take - a well set-up M14 shoots like a dream, but the economics of it make it a pricey item. Used to own an HK91 - shot really well, but it did tend to beat me up, recoil-wise. Also, that delayed roller block assembly can be a royal bitch to contend with when you're trying to clean the rifle out in the field and under some pressure. The FALs I have shot way better than I can, and I could and did afford two of them (plus another kit for spares) for the price of a nicely turned out Springfield Armory M14.
Another StG 58 FAL note - after about 60-80 rounds or so, it does tend to get a bit hot around the foregrip. GLoves of some sort are a good idea for any battle kit.
As harpseal used to say, "Stay well, stay safe, stay armed."
It ain't over yet, not by a long shot.