Home Forums Hunting & Shooting Ask The Gunwriters 280 AI and 270 AI

seems like a rude and uncalled for comment

In my opinion, cases based on the '06 - going AI is not worth the troubles for velocity reasons. I think there are cases that "improving" them is worthwhile, based on increased velocity alone. A few come to mind: Hornet, H&H cartridges, cartridges based on the 250 Savage. But, I finally got my 300 H&H pre-64 Winchester and I would not consider trying to improve it.

I have a pre-64 375 H&H AI and it does get higher velocity than 375 H&H, however, I bought it "AI'd" and got it for about 1/2 price of a standard 375 pre-64. I do not have means to accurately test pressure. (Some of the loads for the 375 H&H AI in Load Data are incredible!!!) I don't mind it being "improved", but the price my kids will get for it someday will be lower do to this "improvement". From what I've read by Ackley and others is that 375 Weatherby data can be used in this cartridge and I've been limiting loads to match Weatherby velocity and it happens to meet the loads of the Weatherby grains of powder wise.

When I built my 375 Whelen, I decided to go AI mainly for shoulder issues and availability of reamers and dies. It had nothing to do with velocity. It was work getting it to feed. A 9.3x62 would have been much easier.

I use 220 Swift data in my 22-250 AI and I believe that is prudent. (That 22-250AI shoots 1/4 MOA or less with full power loads.) This is a varmint rifle and 22 Creedmoor wasn't considered.

My 280 AI, in my opinion, was not enough improvement on velocity to make it worthwhile. I have not shot it enough to say that it significantly reduces case stretching, but I've heard it enough times from others that I suspect it to be true.

Finally, making statements like, "my dog knows more about guns and chambering than you do" I believe is rude and uncalled for also.

funny when the anti gun lib puppets chime like they know something about firearms

AI designs have me puzzled : the .473 AIs have a shoulder diameter of .455”, the CM has a .462” shoulder diameter.
Shorter case body, but not used in the longer improved cases

I’m thinking about a 6.5 280 improved 30 with a CM taper, shoulder diameter of say .460”

Any thoughts ?

338Rules
On that 6.5-280AI.... If you want one you will get one. But a really great rifle builder I know started with a 6.5-06 and then tried at least 4 different chamber configurations to optimize it. There were shoulder angles of 28, 30, and 40. There were different body tapers. When he got to the “final most bestest” version, for which he had custom dies built, he said it was a waste of time and suggested the 6.5-06. So there you go.

Lastly, my beagle doesn’t give a rip about cartridges because she is preoccupied with getting a treat.

Rick,

These days, as another rifle-loony option there's the 6.5 PRC--which has just about exactly the same case capacity in a shorter, 30-degree shoulder case.

Of course I had to have one, so had Charlie Sisk rebarrel my 9.3 Barsness-Sisk rifle he built 15+ years ago on a stainless, short-magnum 700 action with a stainless Lilja barrel. Had Charlie install a stainless Lilja 1-8 twist in the same contour (so I could interchange barrels) and it shoots VERY well. The velocities are just about exactly what I got with my 6.5-06, a Shaw custom rifle made a dozen years earlier....

When firing forming the .280 case .
The case will actually get about .003 shorter.
They dont move much after FF.

Dave

338

My cousin and hunting buddy is building a 6.5-280 AI or 6.5-06 AI, I don't remember which.

If I build a 6.5-06, it will be a a necked up 25-06 with no other changes. (Clearly, there is an huge abundance of animals out in the world that neither the 270 nor the 25-06 would work for an assortment of very valid, important, and significant reasons. Thus my totally desperate need for a 6.5-06).

I don't think the '06 case needs improvement (or is significantly improved) in calibers 358 and smaller.

I do think an AI case looks nice. In most cases there isn't a lot of negatives with the AI case/chambering, though some people do a bad job of chambering the AI. And there is the often quoted case stretching issue.

Less than .01% of my center fire shooting is with factory ammo, so I have a different view in this regard than some regarding the 'AI or not AI' issue..

If you want an '06 or 280 AI case based rifle, that should be good enough reason to do it.

Bugger

Bugger,

After my experience with the 6.5-06, would not build a conventional one--or use .25-06 brass necked up. Instead I'd build a 6.5/.270, and neck down .270 brass--for two reasons:

The .270's neck is longer, which reduces throat erosion slightly.

Necking down .270 brass bypasses the probability of creating the "dreaded donut" at the base of the neck, due to the thicker brass of the expanded .25-06's shoulder.

Good advice MD thanks.

Given Nosler 280 AI brass and a standard style (not the Type S bushing) Redding full length sizing die, the 6.5-280 AI is just as easy as the 6.5-06. I've been working with one lately. It's a very likable cartridge.

Great info here. Thanks

(Excerpted from a few posts up)

First I’ve heard of this. A longer neck in a rifle cartridge tends to equal less throat erosion? Why?

Is it just the slightly increased distance from the main powder column to the throat?

Always preferred the extra grip on the bullet & less protruding of the bullet into powder space but this is another factor to appreciate longer necked cartridges for...

Common folk can get by with a 270 or 280. Never known a deer to understand the difference.

Yup that pretty much covers it.

RinB Your beagle knows best !

The more I look at all these improved, and semi improved case designs, the more I like the Weatherby 6.5 RPM .
Just need dies and a source for good brass. Might want to long throat it a bit in a 700 LA
I’m sure we’ll see a few variations on the RPM case : 7mm, Or even a 9.3 come to mind.

LJB Why not the Redding Type S bushing die ?

More alike than different really. Pressure and Twist being the principal differences between those two.
Plus availability. ;-)

Tight Twisted 270s might become all the rage. Say that fast three or four times , ha

Those 130s spun fast might be just the ticket for whacking coyotes

The Redding Type S dies (either FLR or NS) do not resize the neck all the way down to the neck/shoulder interface. This is true for every cartridge on which I have used them. When necking 280 AI cases down to 6.5-280 AI with the Type S die this "reverse donut" can be too large to fit in the 6.5-280 AI chamber. The standard die on the other hand sizes the neck all the way down to the neck/shoulder interface, which allows the necked down brass to chamber easily. Of course, once the initial neck reduction is done, the 280 AI Type S bushing die (with the right size bushing) can be used if you want to do so.

Yep. Throat erosion is worst right in front of the case mouth, because that's where pressure and heat are highest. A longer neck protects more of the steel.