280 AI questions

Some 280 AI info from PETERSEN BRASS !

Some people refer to it as the .280 Improved. Other people call it the .280 Ackley. On casings made by Peterson, they are headstamped .280 Ack Imp. Whichever way you refer to it, the concept popularized by gunsmith and wildcatter P.O. Ackley, is here to stay. Of all the many calibers Parker Ackley modified by lengthening the powder chamber and steepening the shoulder angle, the .280 Ackley is the only one, so far, that has been adopted by SAAMI. And it is a high performer.

According to Derek Peterson, president of Peterson Cartridge, “The .280 Ackley Improved casing will launch a 7mm, 120 gr. bullet over 3,400 fps. The .280 Ackley has a similar velocity to the 7mm Rem Mag, when using light to mid-weight bullets. It also tends to produce less recoil, and less muzzle blast. When comparing the 280 Ackley with similar size cartridges, it has heavier bullet options than the 270 Win, and a flatter trajectory than the .30-06 Springfield.”

Peterson continued, “The.280 Ack Imp casings made by Peterson are designed for reloading. Our .280 AIs have an ultrahard head, and a thicker web which allows them to tolerate high pressure. It also results in you getting more reloads per case.”

“Speaking to the 280 AI chamber design, the concept was that you could ream out the chamber of your .280 Rem rifle to the Ackley dimensions, which sharpened the shoulder angle to about 40 degrees. Then, after the first firing of your factory loaded .280 Rem ammunition, the casing would fire-form into the new shape. The newly formed case would then hold more powder, and send bullets faster and flatter on subsequent reloads.”

Peterson concluded, “Some people use the made-up term “Ackley-ized” to refer to Ackley’s concept of steeper shoulder angle and taller powder chamber. Sometimes, around our shop, we use the term “Peterson-ized” to refer to how our casings have increased hardness values and improved web design to hold more pressure and get more reloads. To take advantage of both concepts, give the new .280 Ackley Improved casings from Peterson Cartridge a try.”
 
Ok i was just having a debate with a buddy. seams to me like a waste of a cartridge to try and make it faster and flatter by turning it into an AI version and then chopping the barrel back to 22 inches.
To me the purpose of this round was to replicate the 7mm mag in a standard action. Thinking you would want a nice 26 inch barrel to achieve maximum results?
I am no pro on the subject. more curious than anything to get another opinion. seams to me like a cartrige with some pretty great potential.
 
My 25” .280AI is running 150’s at bang on 3000fps.

I’m sure with a bit more goofing around I could probably grab another 50-100fps but the rifle shoots so good at 3k, I have no desire to run it faster.
 
profesional 111 said:
Ok i was just having a debate with a buddy. seams to me like a waste of a cartridge to try and make it faster and flatter by turning it into an AI version and then chopping the barrel back to 22 inches.
To me the purpose of this round was to replicate the 7mm mag in a standard action. Thinking you would want a nice 26 inch barrel to achieve maximum results?
I am no pro on the subject. more curious than anything to get another opinion. seams to me like a cartrige with some pretty great potential.
Click to expand...

I'd be wanting a longer barrel if speed is the ultimate goal: I have a 30-06 with 28.25" varmint barrel that is very accurate and with modest powder charges, quite fast. Primary goal is accuracy, but reasonably high velocity with 208gr is a factor but without getting carried away with pressures.

The 7mm RM is a standard action length round: 2.5" which is within a few thousandths of 270, 280, 30-06, 25-06... actually the 7mm RM is .004" shorter than the 280. But even if one excludes the belt from the diameter is substantially larger diameter body. You simply cannot duplicate the velocity of the 7mm mag with a 280 case capacity unless one creates a bias by pressure differences, but all things equal one cannot overlook the powder capacity difference. I don't see the point in trying to achieve great speed by burning more powder yet chopping the barrel so that more of is burned past the muzzle: Might as well have the small powder charge of the 7mm-08. But there is a happy medium in barrel lengths: where one achieves maximum efficiency from powder charge but not so long as to reach the point of diminished return induced by barrel friction.

Intended use also comes into play: it's impractical to carry a long barreled rifled most places. As to the usefulness of the 280 in standard or AI form? it is a good choice for hunting any large game on this continent. The 7mm mag just extends the useful range a bit... whether it can more quickly heel the grizzly intent on turning you into pooh is debatable: Your ability to shoot true is the most influential factor.
 
IMO 24 inches is a good starting point. A .280 AI with a stout load will approach 7mm Rem Mag factory velocities, with that much powder the extra length can help maximize the velocities. If I was hung up on barrel length I would just look at a 22" .270 or 7mm-08.

One of my open country rifles is a 26" X-bolt in .280 AI. With its 8-twist barrel and a case full of StaBALL 6.5 it should have no problems getting the most velocity out of the 175gr+ bullets. I'm still burning through my stash of Hornady Precision Hunter cartridges to break in the barrel and build up a pile of brass, but so far I'm thinking of Winchester Large Rifle primers cooking off the StaBALL charge behind some AB-LR or Barnes LRX bullets. With a big 4-24x scope and tons of adjustment it doesn't have to be the flattest shooting thing in the world, so long at the bullet stays within its expansion velocity window it's all good.
 
My 280AI is 22.5", and so is a good friends. With RL26, our rifles can push 3125 fps with the 139gr Barnes, and 2950 fps with the 160gr Accubond. If that isn't traditional 24" 7RM ballistics, I don't know what is
 
I don't regret the length at all. Another friend has a 23" on his Tikka build, and it will push the big 168gr LRX to 2800 fps with RL26 even when seating that looong bullet deep to the 3.34" magazine box
 
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