Anyone have any experience with this round?

One heck of a good round! I still build 2 or so every year. Easy chamber to make cases for. Easiest way is to size a 7MM Mauser case to 6.5 to "just" allow the bolt to close and fireform with Bullseye and a cheap bullet or use your own thing. I do mine the hard way with L.C. NM 30-06 brass. Tons of work but the cases last forever. I still have my old BSA in 260 AAR. Killed a lot of deer, a few elk and other stuff.
Aloha, Mark

I've been using my .260 AAR (Shilen barrel on a M98 action) for about 25 years now. Most of my hunting for deer and antelope has involved 120 grain bullets, but it handles bullets from 85 grains to 160 grains with equal accuracy. I've rarely needed a second shot other than for sighting-in. It's an outstanding, well-balanced cartridge. I fireform most of my cases from 7mm Mauser brass necked down to leave a slight false shoulder for headspacing. My fireforming loads with 120 grain bullets are used for hunting as well with equal accuracy and only a slight drop in velocity.

My father-in-law had one built in 1953 on an arisaka type 38. He forms cases from .257 roberts and fireforms to the improved chamber.
unfortunatly he had a 18" barrel installed. Really suffers in the velocity dept.

I had a 6.5-284 instead.

Easier to load for and higher velocity.

I have one built on a Remington 700 SA and it is one of the most accurate rifles I own. Mine has a 23" Montana Rifleman barrel. It is a great cartridge; mine is accurate with everything from 85g Sierra's to the 140g of any make. Bohica told you straight.