I've been shooting a 6.5x280AI for about 8 years now. I have two rifles in that chambering, one on a Montana Rifle Co 1999 action (Bartlien barrel) and the other on a Savage action (Black Hole Weaponry barrel), both 1:8" twist.
I use a set of Redding bushing dies in .280AI with the appropriate neck bushing.
Since I live in West Texas, I have shied away from Re26 due to it's issues with pressure spikes in temps above 95F, finding that Retumbo is perfect in my rifles with 140gr and up bullets.
100gr Nosler BT pushed with a max load (in my rifles) will do over 3,600fps and put five shots in 1/4MOA all day long.
I'm sure it's a barrel burner at that velocity, so it doesn't get used very much.
I've been very pleased with the cartridge and highly recommend it.
Yes, the "Easy Button" is the 6.5 PRC, but I found this before that came out and I'll stick with it.
Ed