I had a chance to shoot an AR-15 autoloader in this caliber this weekend. It is basically an old 30 Remington case head size necked to .270. The standard load is 110 grains. Handloading will go to 115 grains from what I hear. The speeds are in the 2700 - 3000 fps class depending on the bullet weight.
The rifle shot extremely well averaging 1" with factory Remington soft point ammo. I was on surgical call this weekend and couldn't stray far from the beaten path but my friend killed a nice mule deer doe with it at +/- 300 yards. His dad said that it went down at the shot and had expired by the time they'd gotten to it.
Not my first choice for 300 yards shooting but an interesting cartridge...~Muir