I have owned 2 270's, both with 22 inch tubes. Still have one of them. I may have had slow barrels but both of them were pretty much all done at a little under 3000 fps with 130's and 2800 fps with 150's. From reading other postings I am sure that my results were not typical, but that was my experience. Twice.
I like the 277 bore and had lots of Nosler Partitions, 150's and 160's, that I obtained for $10 a box at a sale, so I had a 270 Roy put together. With a 24 inch barrel I have no trouble adding 250-300 fps to anything I was able to squeak out of the 270 Win, and at lower pressures to boot.
Really like the 284 bore also, but where the rubber meets the road there is really very little difference other than what's in your mind. I seriously doubt that a 7 RM or 7 Roy will do anything on game out to 500 yards, which is my self imposed limit, that I cannot do with the 270 Roy.
Opinions vary, mine is that either the 270 or 280 AI versions largest advantage lies in the mind of the owner.
