I have no experience with the 280 AI, (would like to have one in the Kimber Montana), but I would like to comment on the 7mm rem mag and 270. I am with boston, in regards to 270 velocities. I had two 270's, one with a 22" bl, one 24", I chronograghed 130 gr loads from Federal, Hornady LM, and Remington, and none of them were as fast as the factories advertised in either gun. My history with the mighty 270 lasted less than one year.
As for the 7 rm, bea175 says its a clone of the 30-06 with 150 gr factory loads I would tend to agree, acutual with 150gr factory loads I would choose the 30-06. But, when the 7mm is handloaded to its potential, here's what I have found. With over maximum (overmax) advertised loads of RL22, (but safe loads in my guns) here are my results: these loads were chrongraphed in a factory Rem 700 24" bl, ruger no 1b 26" bl, and a rem 700 action with a custom 23" bl. With the same 140gr bullet load vel averaged from 3325fps-3375fps between the 3 guns. I am currently shooting a 150 gr laod with rl 22 that averages 3300 fps in the custom gun. A 270 or 30-06 can't compare to that IMO, and yes these are over maximum listed charges, but it is what it is.
I'd be pretty much inclined to agree with the above except that I can't be down on the 270 for a lack of performance. I've been loading the cartridge since, I think about 1972 in too many rifles to count anymore,and routinely get about 3100 with a 130 gr bullet;some rifles and loads have given close to 3200.
You can play with ballistic charts all you want,but no 30/06 load can shoot as flat to 400 yards as a 270,although possibly the brand new 130 mono's from an 06 may do as well;but that's just one load with one bullet.
Since the 270 has a history and track record on big game that the others are gagging to catch up with (maybe the 7 mag is close today),I would suggest that if you think a jump to the 280AI is gonna make your life simple,you're mistaken.
Except when I have deliberately built 270's and 7 RM's with over-sized groove diameter barrels,I have generally not had to exceed published data to get the velocities I have posted,from either the 270 or the 7 RM.
I think the above posters velocities from the 7 RM are a tad higher than I have encountered with the 7 RM; I generally settle on 3250 or so with a 140;routinely get about 3180 with the 150,and a bit under 3100 with a 160;and I am not fire walled with any of these loads from a 7 RM.The AI seems to max out at 3050 with a 150.Why bother,from the same barrel and action length?BTW all shoot flatter to 500 than anything you force down the barrel of any 30/06.
It's pretty apparent that there is little to choose between these cartridges and the reason I am not all in a lather over the 280 AI is not because it's not "good";mostly because it is not popular(never will be),brass is hard to get,and its' ballistics are easily duplicated by commonly available cartridges that I can get at WalMart, or about anywhere I typically hunt big game.
The 280 AI is kind of like mammary glands on a bull;udderly worthless,but interesting to speculate upon.....
