Whoever told you that BH ammo is unsafe in an AR is sadly mistaken or works for Federal!
Seriously, all flavors of BH .223/5.56 ammo, particularly their 77gr SMK Mk262 loads, runs like a scalded dog in all of my ARs. Never a single ammo-related issue in any of nearly a dozen ARs I have used BH ammo in. Same with the BH 308/7.62 ammo in my AR-10 and POF P-308 rifles! Same holds true for the Corbon offerings.
While I can't speak directly to the .260 Rem ammo from BH or Corbon, I cannot imagine that it would have any problems functioning properly in an AR-10/LR-308 platform rifle and offer excellent accuracy.
The BH that I'm talking about is that 260 ammo that GAP had made. I believe George said it was too hot to be semi auto safe. I could be mistaken though.
I have a stash of the gap 260 black hills. I havent chrono'ed yet but I can assure you it is on the ragged edge of too hot in my GAP bolt gun. I dont think I would put it in an ar10 type platform. It flattens primers and shows faint extractor marks in my gun. Shoots phenomenal though. I watch it pretty close down here in SE NM in the summer time. No 115 degree shooting days for me with that ammo.
the BH 260 ammo will operate fine in an AR, the problem is it's not accurate from an AR. I went through a case of it and it was 1" at best. I wouldn't shoot it in an AR again. Now a bolt gun, that's a different story.
If you go to GAP's website and keep refreshing you'll see two different pics of the rifle. One will say "Just like dentists" and will have a bald guy shooting an AR, and the other will say "Balance" of the same guy prone, pointing at the camera. Those are a picture of this rifle with the 308 upper. With the exception of the muzzle break the 260 and the 308 uppers are absolutely identical.
Must be they took the "dentist" one down all I find is the "balance" one. Nice stick. I'm going the same direction but might cut the barrel back to 20" and put a QD muzzle break on it. The barrel is a 24 now.