Home Forums Hunting & Shooting Ask The Gunwriters Want to get a 280 AI?

so it appears that the love for the 280 AI revolves around 2 things, that being AI people run at max or slightly over standard pressures. couple that with pretty anemic 280 factory loadings and guys really think they are doing something if you limit yourself to the lower pressure data and a guy comes along beating that by over 100 fps with an AI, then everyone jumps on the bus.

I did some checking in my lyman 48th for 140's and 150's the top book loads are faster for the 270 despite being a smaller bore. so once again muledeer summed it up, 50fps with equal pressures.

There are a couple of small advantages to the .280 AI. The cases don't stretch much, typical of AI's, and the Nosler factory brass is made by Norma and hence excellent.

In fact, the brass is why I did my own .280 AI. Nosler gave me some, so of course I had to obtain a rifle to use it!

Well JB, I used to buy the dies first to justify the gun, result is the same but it's obvious you still have your "rifle loony" credentials. I have a M700 ADL combination gun in 280AI and 7mm Rem Mag. When I want the 7 mm mag I use my handloads and when I shoot 280 AI's thru it I buy 7mm Mag factory loads pretty trick huh? saved the die money for beer that time. Magnum Man

That might even be called anti-loony!

Did you drink the beer slowly?

As someone who has been circling the 7mm kool-aid punch owl for a while <grin>, I can report that it's the single most hotrodded bore size there is! You will see the craziest claims made for speed... WAY over what the books say.

I attribute it to the fact that the 7mm bore size naturally attracts folks who like to gack and tussle over ballistic minutia, since in many ways the 7-bore often wins those tussles.

(actually, my 2nd and 3rd hunting rifles were 7mm's ('08 version) so I've secretly been sipping the koolaid for a while now... grin...)

Yes very slowly and I only opened it after the bottle started to sweat and after it sweat enuf I drank it slowly, then repeated the process 2 more times .Which was enuf to forget about 280 AI's and went to my favorite gun shop to trade for a 280 Rem,that is a really different outfit you know?Funny thing about that St Pauli girl leading me astray and giving me ideas, illusions of grandeur as I was tipping up a bottle my eye caught the Hornady catalog laying there. Sure enuf, I opened it and Hornady Light Mag SST ammo for the 280 Rem with 280 AI performance.... only 2 guns but 3 cartridges. Go up or down to the AI without buying any new dies. More money for St Pauli girl. Magnum Man

If you shoot a 7mm magnum (or any magnum) you're tagged as a poseur but if you shoot a .280 Ackley Improved you're tagged as an aficionado!

So did you lick the sweat off The St Pauly girl??????Just wondering!!!

Where does one find 65Ksi pressure tested load data for the .280 Remington?

Or are you on your own in determining when you reach 65K?

Using only published data the AI version is 100 to 200 fps faster.

Well practical or not...seems real cool and I will have a NULA .280 ACKLEY next week. It was the same LH .280 that Boddington tested for G&A last summer. Worked out a deal with Melvin and he Acklyized and repainted it and I am planning to shoot the hell out of it. Prolly have 1500 7mm 150 gr bullets of various flavors plus a bunch of Amaxes that have been molding away on my bench and they are going to get launched.

Lefty C

I've never been called a poseur before, a hoser maybe...Ah Huntz, no I didn't but will take your advice under advisement sounds like a safer idea than what I was thinking. Magnum Man

I'm jealous.

What kind of velocity would a 7mm Magnum get if loaded to 65,000 psi? It seems only fair to load them both to the same pressure.
whelennut

Well this is how I always felt about it....I built a 7 1/4 pound 7RM back in the early 80's with a long throat that would pile composite groups;drove 140's close to 3300 and 160's at 3125....hunted and shot it till the barrel quit in the 90's.....

I also knew by then the 280 would do 3080 with a 140 from a 22" tube,and better with a 24" and RL22,because I had those, too....when I learned of John Sundra's 7mmJRS I thought it was nice but did nothing I couldn't do with a 24" tube from the 7RM, and much easier.

These days I look more to the rifle than a middle of the road, capacity wise, cartridge like the 280 imp.

When I handle a Kimber 84L I will know if I like it better than the 8400 WSM's. If it stands out handling wise I might consider one in 280 imp.

Right now I have WSM's in Kimber Montanas and 84M's as well. Can't see the 280 imp. beating out a WSM. However the rifle might.

Somehow I doubt it. Its just another cartridge.

nsaqam,

The .280 AI data in the Nosler Reloading Guide 6 was developed with the SAAMI 65,000 psi limit.

The SAAMI limit for the standard .280 is 60,000 psi, supposedly because it was designed for the Remington pump and autoloading rifles--despite the fact that both rifles were also chambered for the .270 (65,000 psi). But that's the big reason the .280 AI data shows such a big advantage over the standard .280.

Low factory pressures for standard cartridges are often the reason AI rounds show a big velocity jump, leading some innocent handloaders to believe a few grains of extra powder capacity works miracles. I have read articles over the years about supposed wonder cartridges such as the .250 Savage AI and the .35 Whelen AI, where the author compared factory muzzle velocities with (usually warm) handloaded velocities for his AI rifle.

The .250 AI does gain quite a bit of powder room, due to the tapered case of the .250 Savage, but the .35 Whelen AI probably gains the least amount of powder room of any Ackleyed round.

FWIW,

I just went back and checked my load records for my .280 RCBS Imp.- nearly identical to the AI version, 30 degree vs. 40 degree shoulder.
Rifle is a custom Ruger #1.

With my best load of RL22 and 140 gr. Nosler Partitions, MV is 3150 fps.
With factory Fed. Vital Shok ammo, and 140 gr. Nosler Accubonds, MV is 3100 fps. Accuracy with the factory stuff is as good, if not slightly better, than my handloads.

50 fps difference is just not worth the hassle, IMO.

Yes, I understand that, but where does one find 65K data for the regular 280?
If the only published data for the regular 280 is 60K how does a normal handloader reach the 65K that the AI version is loaded to absent pressure testing equipment?

The point I'm trying to make is that unless one can find 65K data, (either published or measured yourself) for the regular 280 then the 100 to 200 fps AI advantage is the reality.

The same calculus applies with regard to the 280AI vs. 7mmRM comparison.

If the published load data for the 7mmRM is limited to 61Ksi (SAAMI)then the 280AI, loaded per the published 65Ksi load data gets velocities very close to the RM.

Well, there are two ways to at least get a reasonable estimate of 65,000 psi in the standard .280.

One is to use the old ballistic rule of thumb that pressure increases at twice the rate of velocity. Thus, if we have some standard .280 data that suggests 3000 fps is tops with 140-grain bullets, we can do some figgerin' and come close.

65,000 divided by 60,000 = 1.0833. From this we can figure that a velocity increase of about 4% (half of 8.33%) should result in 65,000 psi--or even less, since most handloading data isn't right at the top anyway.

3000 + 4% = 3120. This should be a safe maximum velocity in the standard .280, given a manual-listed 60,000 psi maximum of 3000 fps.

We can also measure the difference in case capacity between a standard .280 case and the .280 AI. I've done this and IIRC the difference is about 5 grains.

Let's say the .280 holds 67 grains of water with a 140-grain bullet seated. This means the standard .280 holds about 62 grains--again a difference of about 8%. This time, however, we use the 1/4 Rule, that any increase or decrease in case capacity result in 1/4 that amount of potential velocity at the same pressure. Thus the .280 is capable of about 98% of the velocity of the .280 AI.

If the .280 AI can get 3250 fps from a 140 in a 26" barrel (and the Nosler data lists 5 powders that do that), then the .280 can get 3185 fps when loaded to the same pressure.

Now, that's in a 26" barrel. For a 24" barrel we subtract 25 fps per inch, and come up with 3135 fps. This pretty much agrees with the number we got with the other method--and is pretty much exactly what I tend to look for from the standard .280 when handloading.

Of course, that depends on the bullet to a certain extent. When I was hunting with the .280 a lot, my rifle was a custom Remington 700 by Dave Gentry with a 23" barrel. My light-bullet load was the 139 Hornady Spire Point Interlock and 60 grains of H4831, at around 3150 fps. Typically Hornady Interlocks develop a little less pressure, on average, than most other bullets, so can be safely pushed a little faster.