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

Since the 280 AI has become so popular I couldn't help but wonder why a 270 AI wouldn't also become popular if promoted by the gun press and manufacturers ? I understand that we don't really need a 270AI but then again one could argue that we didn't really need the 280 AI either and yet it has become wldely used and available.

Common people who don't twist turrets, own laser ranger finders, or feel the need to shoot VLD bullets buy 270s and are blissfully content until told differently. Sometimes good enough really is good enough.

The 280AI is a vehicle for those in search of elusive perfection, higher speed without the recoil. The 7mm SAUM is a short action 280AI, but it is about as under appreciated as it could be.

One factor is the .270's SAAMI maximum average pressure is 65,000 PSI--as high as they allow for ANY cartridge.

Half or more of the reason the .280 AI gets more velocity is SAAMI's MAP for the standard .280 is 60,000 PSI, because it was originally introduced in Remington's semiauto rifle. When SAAMI accepted the .280 AI they standardized the MAP at 65,000.

Just "Ackley Improving" most rounds doesn't gain much extra powder room, and in fact in some basically none--as in the .35 Whelen AI, because there's no enough shoulder there to gain significantly more room.

The reason reason most Ackley Improved rounds gain significantly more velocity over the standard version are handloaders "work up" loads until they see "pressure signs," then back off a little. This generally means pressures a lot higher than data or factory ammo for the standard rounds.

About the only real advantage in AI'ing any cartridge is reduced case-stretch, due to the sharper shoulder maintaining headspace more firmly in the chamber.

Mule Deer please don’t tell Dogzapper that. It will break his heart.😁
GreggH

Having limited experience with AI's, I don't see this as a minor thing. It has been right up there with sliced bread for me shooting and loading for an AI. The cases don't seem to budge even a little in several firings.

It's not a little deal--especially if you shoot a lot of "colony varmints" with a .223 AI.

On the other hand, many newer commercial cartridges have shoulders steep enough to do the same thing. 40 degrees isn't actually required; 30-35 will do as well if you're careful when setting the sizing die.

Are AI cartridges more accurate due to better brass fit in chamber?

I shoot a 270 improved it is called the 270 WSM. It doesn't eclipse the 270 Win. by all that much, most loads only gaining 100-150 fps. I can't get 130s to 3,400 fps like some claim to and much over 3,300 is pushing it in my rifle. The WSM is only moderately popular and it is hard to compete with the original 270.

I would not be surprised if the 6.5 PRC out sells the 270 WSM. As Mule Deer wrote with out the pressure advantage the 280 has the 270 AI doesn't gain that much and uses a grain or two more powder just to get up to the 270 Win. speeds. Real world it will gain 50-100 fps over the standard.

The AI can show an accuracy gain but most of it is due to custom reamed chambers. Ackley claimed improved powder burn but this hasn't been proven. It does produce more uniform pressures with a 30 degree shoulder being optimal, the 40 has some of the same effects.

The shoulder angle has no effect on accuracy, but some claim a shorter fatter case does improve accuracy.

Ahhh the brutality of truth!

I have had a 270 Improved in a 15” pistol barrel. I loved it & it was very accurate. The 130’s would run 2950 fps.

I have two 280 AI’s. They are both customs and very well capable of making me a one gun hunter.....if, I wanted to be.

my dog knows more about guns and chambering than you do

PO Akley said .270 W was one of the cartridges that did not improve, likely because of the MAP being what it is.

I thought most of the powder volume gain was from lessening the body taper, not just the little shoulder angle increase? If that's the case then the volume increase would be close to the same on the .35 Whelen as it is on the .280 AI.

Not saying any of it worth it, just trying to understand.

AI's do look cool.

That was enough for me to try it (once) with a 338-06 IMP.

Made no sense but I do love the round!

std 280 with a 9", 24"
160g-162g
IMR 7828
Fed 210
Win brass
2930 fps
Load right out of the Nosler #4 manual, not for pumps and semi auto's, and Nosler reduced the load in later manuals

Also, the 280 AI shoots the 175g-180g at the same speed.

No flies on a 180g ELDM at 2800 out of a std 280 with Lapua formed brass from '06....about as idiot proof as they get....in the AI with Lapua '06 brass, you are looking at 2900+ depending on your barrel bore dia, throat dia, and bbl length.

I copied this load from another member here, everyone that shoots the std 280 with the 180 eldm wants one. A .796 BC at 2800 with match accuracy is impressive, to say the least. Not much powder, recoil with a brake and limbsaver is pure Honey!

There's not much taper in the .270, .280 .35 Whelen case to remove. Even with the sharper shoulder and less taper, the .280 AI only gains about 4 grains of powder capacity over the standard .280--which translates to about 50 fps of velocity gain in loads around 3000 fps, with both cartridges loaded to the same pressure in the same barrel length.

But the .280 AI also gains about another 100 fps over the standard .280 due to a higher SAAMI pressure for the .280 AI, 65,000 PSI versus 60,000 in the standard .280.

Which is why I would choose the 280 over the 270 only if I was a handloader. And at that one willing to develop my own loads.

Thanks John. 👍

I can follow all that. What confuses me is no one ever promoted a 270-08 or 25-08 for that matter. I know both are recognized wildcats. Only ever read 1 article on the 25 super (not sure of the spelling) by Van Zwoll I believe. Seemed intriguing. So...... why no 270-08?

While probably not the issue today with Re 15, the 375 Wby/AI can pick up 200 f/s over the standard H&H and especially with long spitzers. 4064 burn rate is a bit fast for the H&H and the 4350 burn rate a bit show but easy to get full pressure loads in 375 Wby/AI with 4350.

Actually in the late 1960s in Australia the 270 Imp and 218 Bee Imp (On Martinis) and that was because of powder. We mainly had the old 4831 which was a bot slow for 100 grain Hornadys in the 270 so the 270 Imp did better than increase incase capactity would suggest. For the 218 we had 4740 which was used in Canadian military 303 and like 3031 burn rate and too slow for the 218 and so the 218 Imp.

My feeling, that is I am not 100% sure, is a sharp shoulder and parallel body seem to speed up the burn rate of powder.

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.

The theory was (and, I suppose, is), if a line drawn along the angle of the shoulder, hits within the neck, throat erosion will be reduced. I've never seen any concrete data to back this up but it makes some intuitive sense. Geez, I hate trying to type anything on this damn site. I'm outa here! GD

LJB Thanks, that’s the first I’ve heard of this “ reverse donut “ when necking down with the bushing dies, but it does make sense. Thank you for sharing your experience.

This throat protection is why I’m more interested in the 6.5-280 AI in a long action.
The 6.5 PRC has lots of features to recommend it though.

An overlooked benefit of going 'Improved' for some is going to a shorter barrel and getting the same velocity as you had for a longer barrel.

Example, my high country backpack rifle was a Remington 700 Ti in 260, 22" barrel.
I installed a 20" factory take off 260 Rem that was Improved with a 40 degree shoulder.

This made it for me, a much more comfortable rifle to pack and more handy just having two less inches barrel, and 4 ounces less.

Anyone who has packed in and hunts high know this. Ounces and inches count overall and it makes a positive difference, and I was still able to maintain the original velocity when it was a 22" barrel.

Shots were long, even to 700 yards, and that little extra speed made the difference for that 20" barrel, and I could maintain my scope settings.

I would think that if going 270 Improved, if you could find that sweet spot powder (maybe a little slower powder) for the particular bullet weight you want to shoot, it would be worth it. Fun for sure trying anyways!

The 30-06 Improved is in my sights now, another one worth investigating. I have an 8lb keg of IMR 4831 that says yes!

I found a 40-page Australian military study from 2005 that looked intensively at barrel erosion, "Understanding and Predicting Gun Barrel Erosion," put together by Ian A. Johnston. It is by far the most comprehensive collection of information I've seen on the subject, and where I obtained most of the demonstrated info on barrel erosio-including info on neck length and shoulder angle I summarized the findings in a magazine article quite a while ago, which was eventually expanded into a chapter in GUN GACK II.

The only cartridge that looks like it would truly benefit from an "AI," would be the 6.5x55mm.

... but have yet to find the need.


Other cartridges, like the .270 WCF, cover that nicely.




GR

I like that idea of going improved with some cartridges and shortening the bbl. Makes sense.

Somewhere in PO Ackley's writings he said the only cartridge he couldn't really improve was the 270W. I figure it's just really hard to improve on perfection.....

I built a 30-06 AI in the early 90's, and it ended up liking IMR4831 the best for accuracy and velocity. I used both 180g X-Bullets and 200g NPT's. Killed two moose, two caribou, two elk, a deer and a pronghorn with it. IMR4831 can be temp sensitive though. If I had to do it all over again not sure I would that again though.

Interesting read. I went through the AI thing more than a few years ago, with my first, a7x57 AI. Course this was before LRF and dialing scopes..the added velocity gave me a little insurance, case I mis-judged distance to a target. MD is exactly correct..I pushed the case, cause it was "Improved". The cases didn`t last long, primer pockets went first. I then had to FF new cases. That got to be a PITA. I think I got a little smarter. I now have a standard 7x57, LRF, and dialing scope for 'Long" shots. Can`t say I miss the "extra" velocity, case problems, etc. If I need more snort, I use a different tool. Sounds like we all have them...tho I still have two AI`s.

Has anyone lost velocity when going AI? That is what I experienced when I converted a 243 to 243 AI. I had to increase my load by 2 grains to get back to were I started. It does look cool though and gives you something to talk about at the Range.

TEXMAG

Increased case volume. Same amount of powder as before in a larger case equals less pressure, and that equals less velocity.
The idea of an improved cartridge is to primarily increase powder capacity.

My point exactly, you use most of what you gain to get back to were you where. The brass does look cool though and doesn't need much if any trimming.

TEXMAG

It's been done, was a guy down in Arizona or somewhere down that way loved his BLR 1 st generation you know the one that the mag stuck out 2" at the carry balance point anyway he liked his blr more than his bolt 270 but liked.277" bullets. So he designed a reamer on the 308 case to 270-308 , bought a 24" Douglas barrel had his smith thread it a cut the chamber.he claimed by chrono that he could get 3000 fps with 130's and ball powder. Of course like everyone else it all but shot one hole groups. That article was in either Rifle or Handloader way back when in 2 digit issue numbers. That guy is prolly 80+ years old now if he survived and didn't get aids from using that gun and cartridge. Probably damn near get the same ballistics in a 308 with 130 ttsx loaded hot without risking your health or bank balance. Mb

Magnum Bob
Long ago there was the 25 Durham which was an “improved” 308 necked to .257. Pretty fair outfit.

Before that there was a 270 on a 300 Savage called the 270 Titus. Was created by Utah barrel maker Bliss Titus. He converted 99 Savages.
There were 1950-1960’s vintage.
Rick

Back to the 6.5-06 versus 6.5-270 or 280 AI. All of them can still use the 06 brass it will just be short and may never need trimming. I am not sure how many rounds you would need to shoot to see scorching at the front of the chamber but if shooting 38 special in a 357 mag chamber is any indication you would scorch the throat before the chamber became a problem.

There were 25&27 IHMSA's on both the Savage and 308 cases for silhouette shouting.

Having owned a couple of supposedly, "barrel scorchers" for over 50 years, I have yet to see any issues. Of course they are only fired 20-30 times a year, because I use other rifles for casual shooting and to maintain proficiency. I will be gone long before they are worn out.
I cannot believe that a 280 bullet fired from a .270 case is going to be much different than the same bullet fired from an 06 case. I use Nosler or Hornady brass for my AI, no need to mess with fire forming. Early on when I did not have cases specifically for the AI, I necked down and fire formed 06 cases, which is a waste of time and energy if commercial brass is available.

Kinda fond of the .270/.270 myself. Usually load it like a hot 7x57.

Tag Reverse Donut Type S Bushing

I still like my 250-3000ai. 100 grain bullet at 3200 fps has killed a bunch of deer. By the same token I’ve played with a bunch of other ones and found the difference to be minimal. Still enjoyed working with them. There are so many great rounds out today the need for AI stuff is not what it once was imo!

According to P.O. ACKLEY FIREFORM IMPROVED WILDCATS FROM CURRENT FACTORY CARTRIDGES

"... But the 270 Winchester Ackley Improved was a different story altogether, another customer request that resulted in a wildcat inferior to the standard cartridge.

P.O. wrote that the standard 270 was already "overbore," so a 40-degree shoulder with minimum taper couldn't offer much improvement, if any."


P.O. ACKLEY FIREFORM IMPROVED WILDCATS FROM CURRENT FACTORY CARTRIDGES
Cartridge:
270 Win. Ack. Imp.

Performance Gain over Factory:
Little or none with more powder

Ackley Comment:
Not recommended, factory 270 is better




GR

Lot's of common folk never heard of a 280 either.

After building and hunting with 257AI, 257AIR, 250KragAI, I would say don't AI [Ackley Improved] anything. It takes an extra step of fireforming.


But the 280AI has Nosler brass available.
https://www.midwayusa.com/product/1021411695
No wasted time on a extra trip to the range.

I Have a 270 AI, fun to do it, picked up some speed. But is it worth it? Sits in the safe, running a .257 weatherby.

No doubt this was also in part due to the more limited selection of slow burning powders available at that time. That is not to say that I am suggesting it is worth doing today. I have a 6mmAI and appreciate what I learned about reamers and reloading while working with it but I would not do another one.

Many people when they go AI are wanting the most form a cartridge. They also will make changes to the reamer design to better suit brass dimensions, and bullet position in relation to the shoulder/neck junction on the brass. Brass trimming is over when you go AI.

I have seen note worthy increases in speed with extremes in accuracy with:

223 AI
22/250 AI
243 AI
6 Rem AI-long action case at it's best

Figure 200 fps increase(223 AI-150 fps increase), and none of them are short barrel rifles.

I have shot out quite a few barrels with the parent cartridge with target chambers, then went to the AI version. I never felt like there was a down side to the AI version in the above. I was usually fire forming on Small varmints or Coyotes. Fire forming loads are very, very accurate.

The only big game cartridge that I have played with is the 280 AI.

In the std 280, I shoot the 160g partition at 2930(IMR 7828 with a Fed 210 giving the best accuracy), a load right out of the #4 Nosler manual. In the AI, that same bullet is doing 130 fps faster, R#26, Lapua 30/06 formed brass, 26" barrel vs 24" on the std 280. I now run the 175g ELD-X in the 280 AI. Some would argue that running the 162g ELD's in the std 280 would be prudent vs going AI, and I can not argue with that train of thought.

When I lived in Az, I met a gentleman at the rifle range that was shooting a 26", 30/06 AI, 180's at 3000 fps verified with my Ohler 35P chronograph. The accuracy was very impressive with his 30/06 AI with the 180g Sierra BTSP and 180g Nosler Partitoins., I did not know his load or particulars on chamber dimensions other than he was shooting Winchester brass. I saw the gentleman shoot his 30/06 AI often, and it was impressive to say the least out to 500 meters.. Up until that time, I thought that the 7/08 AI, 7x57 AI, and 30/06 AI were a waste of time, but that one gentleman made me question my closed mind. I have purchased the 7/08 AI dies, reamer, and barrel.....as far as I have got in 5 years.

AI shooters are often using Lapua and Alpha brass parent cases to fire form with, and I use 14.6g of Bullseye with cream of wheat to fire form my 280 AI brass from Lapua 30/06 cases. The primer pockets on the Lapua '06 brass is so tough it is hard to believe. There is no doubt that 100 cases will last a barrel's life time.

I found the Lapua 22/250 and 243 brass to be very tough also when it relates to tough primer pockets, with Federal brass in all AI's being solid junk.

Rifle loonies are often chasing the smallest details on trying to get the most accuracy with velocity, it is a hobby with in a hobby no doubt.

As we see advances in the BC of bullets, there are some combos that are simply mind boggling, and the std 280 Rem, with brass formed off of 30/06 brass, with a 180g ELD-M is simply a game changer. R#17 with a cci 250 with only a little powder can replace a lot of magnum cases, and is killing deer and hogs, 2700 fps on a bullet with a BC of .800 sheds a lot of light.. I am running a Bartline 3b, 5R configuration, 8T barrel, at 24" in one std 280, and factory 280's in others.

Running quality brass with High BC bullets replaces a lot of BS, AI or no AI. Good chambers that take into consideration neck clearance and bullet geometry is a game changer if you are wanting to shoot to 600 yards with extremes in accuracy. Taking Magazine length into account when considering the Cartridge Base to Ogive pays some big dividends, choose wisely and consider how the leade grows 800 rounds from new chamber.

.

The AI offers an advantage in only magazine capacity. For a hunting round I can't say having 3 in the mag ever was too little for me when I have carried magnums from 7MM Mags all the way up to 458 mags. So that advantage may be more a "good feeling" then a real world advantage. Heck, I have often hunted with single shots and still never found them to be at a disadvantage. But extra rounds in the mag can't hurt.

If ballistics are what is being pursued, (more speed) the 270 Short Mag, or 270 Weatherby both beat the 270 AI and do so with FAR less bother. You can buy brass for them both and not have any need to fireform first.

Same with the other AI shells.

257 AI vs 257 Weatherby or for that matter the 25-06, So in the case oif the 25-06 even mag capacity advantage is non-existent. 25-06 holds just as many rounds in the mag and does everything the 257 AI does and sometimes a bit more.

6.5 AI VS the 264 Win mag---- and nowdays several other hot offerings.

30-06 AI vs any of the many 300 mags, all of which beat the AI in velocity.

AI is more of a fun game for those that like fireforming, messing with brass as a hobby and for some, bragging about how "advanced" they are in their understanding of rifles. But for practical use, they offer nothing you can't buy off a gun-shop wall, and the ones you can buy from a local gun shop (or even Walmart) give HIGHER velocities without needing to buy more expensive dies and use up powder and primers to fireform.

I read all the great things about the 280AI. I already had 280’s.
The rifle I bought was a gunsmith build with blue printed 700 action 26” premium varmint barrel etc.
So far my old 700 280 with a stock I carved (not well BTW) shoots tighter groups. But I’ve shot a lot of paper with that rifle.
I really have not spent time and have shot < 1 MOA groups with the 280AI but I expected more and the rifle is pretty heavy even in the light Kevlar stock. I’ll likely try to ring it out this year.
I don’t think I should have spent the $’s what that 280 AI cost. I already had a couple 7mm RM and I didn’t need the extra 50 or 60 FPS from the AI over the 280. I might shoot a lot more at paper with my hunting rifles than most, but the stretching of cases with a 280, I think, is over stated.
As far as 270 shooters, most seem to think they already have the perfect cartridge and there’s no better than perfect.

what about Charles Newton`s 256 Newton anyone do any of the new type powders ? and have some velocities with bullet sizes or how does it compare to these other cartridges posted on this site ? i have been thinking about chambering a rifle in this neat old cartridge. what i really would like to do is have a Ruger # 1 with a Brux barrel 8 twist 26 inch length chambered in a 256 Newton ,its just a dream so far. i did have a 25 Wallok and Holmes rifle using a 270 Win.case but rebarreled this rifle to a 257 Roberts for my daughter. also thought about a 6.5 / 270 Win. A.O. instead of a 256 Newton ? there sure are a lot of options out there to play with . my good friend Greg a a very good machinist and bench rest shooter rebarreled a rifle too a 280 A.O. and after a couple of years wasn`t that excited about the 280 A.O. anymore said it was accurate but just wasn`t his thing anymore. so maybe i may just stay with what i have been using ?

I have done the AI thing several times, and the only advantage I could find was in less case-trimming--sometimes.

My first one was .257 Roberts AI in a New Ultra Light Arms Model 20, with a 24" barrel. It shot very well, and I could see the added velocity on the chronograph, but never could see any advantage in "killing power" or trajectory, because it only got around 100 fps more than the standard .257 when loaded to the same pressure.

Have also had a couple of .280 AIs, and also never could find any advantage there either. Both were very accurate, but so have been my standard .280s--and my .270s.

There was also a .35 Whelen AI, a used Remington 700 Classic that somebody had punched the chamber on, thereby cutting the rifle's resale value in half. (Some shooters pay a LOT for unaltered Classics.) I figured it was worth playing with, and also quickly figured out the .35 Whelen AI was just about useless, because the added capacity gained by blowing out the minimal shoulder of the parent case didn't mean anything. (Had never had any trouble with headspacing in standard .35 Whelens either--another claim of an advantage in the AI version). So I "parted out" the rifle, selling the barrel, stock and action separately, actually making more money than I paid for the rifle.

The last AI I fooled with was a .223, because so many people talked about the great velocities, some claiming to get close to .22-250 zip. I found the extra powder capacity gained (measured with the water method) wasn't enough to get .22-250 velocities at the same pressure, so I ran a test with a standard .223, adding more powder until "pressure signs" showed up. Guess what? With the zippiest "safe load," muzzle velocities were just about what most people claim for .223 AIs. This was because my handloads were getting a LOT more pressure. (Traditional "pressure signs" often don't show up until around 70,000 PSI, something I determined with the help of the folks at a piezo-electronic pressure lab years ago.)

Eventually I concluded that most of the extra velocity from AI rounds is due to their being handloaded to higher pressures than the parent case--though of course some compare their AI handload velocities to factory load velocities. This is why the .250 Savage AI is claimed to be such magic: The SAAMI pressure maximum pressure for the .250-3000 is really low.

Also decided the only real advantage at AIs is less case stretching, due to the sharper shoulder headspacing firmer in the chamber. But a lot of newer rounds have steep enough shoulders to do the same thing, right from the factory.

Maybe one interesting thing some manufacturer could do is get a saami approved 270 AI with fast twist to take advantage of heavier bullets coming out for the 270. Since apparently it is too confusing for them to just fast twist a regular old 270 or 270 wsm. Kind of ride on the 280 AI, high bc, plus new military round trend

Have you heard of the 6.8 Western?

Ha, yep. I have one. Competition, however, is healthy from what I hear

Lou

I was going to improve the .270 with a 30 degree shoulder and take the diameter out to about .454 for a mild improvement that would still ensure good feeding. Unlike the .280, the .270 with its longer neck gives too long a neck if you want to headspace a standard .270 case in the improved chamber to fireform the case. You can of course trim the neck for a shorter case. If you have the improved case's neck shoulder junction higher than the original junction and gain a slight increase in power space, then you have to create a false shoulder by necking up to 30-06 then back down to .270 Improved or fireform by jamming a bullet seated out further into the lands. Neither of these methods are as desirable or as safe as being able to fireform an unfireformed case that headspaces correctly. With the .280, this problem doesn't arise.

A tad confusing, but sounds like you’re trying to set a false shoulder for forming to a 30 degree Improved case.
I’m not sure if the 280 std case differs that much with its shoulder only .050” forward compared to 270 Win

Taking advantage of these new Quick Twist barrel / bullet designs is most tempting. No point launching the big long heavies in anything less than an Uber Improved case.

Have a look at drawings for the SA CreedMoor, it has a shoulder diameter of .462” giving minimum body taper, Combined with that desirable 30 degree shoulder for pressure consistency.

The longer the neck, the better for protection from throat erosion , Plus tons of latitude for seating depth.

I’ve been thinking along these same lines for my LA 275 Improved Express BangN Thunder Uber Improved Cat

Cheers

To me the '06 based cartridges are great candidates to AI, assuming the rifle will feed them. I wouldn't take a good shooting .270 or .30-06 and ream to AI, but would do so upon rebarreling a rifle that I planned to rebarrel anyway. Outside of feeding, and most of my CRFs feed AIs fine, I can't think of a disadvantage.

Loaded to normal pressures, in theory, the AI brass should last a long time without much stretching, which eliminates one step when reloading and I'm all for that.

I fire-form factory loaded ammo in AI chambers for brass and generally without much loss of velocity or in the case of the .280 AI, I just buy brass. I have in fact, fire-formed ammo on animals while hunting!

I don't expect AI cartridges on an '06 cartridge to produce much more velocity than the original and really don't try to achieve it.

If the neck is too long, my concern is too much grip on the long projectiles and too much pressure. If you increase the shoulder diameter in a .270 much more than around .454", then you start to run the risk of compromising very smooth feeding.

6.5 CM feeds well. Does it feed better than the Swede ?
Probably depends on the action just a bit. Many of those actions were designed specifically for one cartridge only.

The 222 Rem has a very long neck ( for caliber ) , yet produces stellar accuracy. Neck tension is more about sized diameter, and neck thickness.

It’s really not that big of a difference from the 280 AI case for a 270 Improved. PO. Ackley didn’t recommend it because of the basic 270 Win cases pressure level. Hence the RPM, and 6.8 Western cases

Great thread - enjoying the context that JB adds. I’ve got several 338-06’s now & considered sending an AI reamer thru one of them but I think I’ll serve my serve inner loony by sending the rifle to JES for a rebore to 9.3x62 instead of the AI path.

You’d like a 9.3x62 I think. I love Whelens but since I had a few and got a stinker of a Hawkeye in 280 I decided to try the 9.3. It has been a silly easy cartridge to work with, just like the Whelens.

Pints : Does the 9.3 x 62 clean up a .338-‘06 ? AI ?

Who wouldn’t want one of each ? Smooth feeding of course.
CZ made a mistake discontinuing the 550, at least in that chambering.

Not to torpedo Rolly

I don’t know if a 9.3x62 will clean up - I’m assuming it/they would but I have no facts to back that assumption. I’ll have to call JES. I’m with you on owning both! The rifle is a Douglas barreled Ruger 77 but after buying my Weatherby ultralight in 338-06 it doesn’t see any field time.

Back to Rolly

The .338-06 is a longer case than the 9.3 which would mean setting the barrel back one thread perhaps as well as re-boring the barrel.

Sorry, but you don't know what you're talking about. While the .338-06's case is slightly longer than the 9.3x62's, that doesn't matter because the 9.3's neck and bore are so much larger that reboring eliminates the .338-06's neck.

Thanks JB!

Looking at some of the chamber specs for the .338-06 show a diameter of the chamber as .369", .370" at the mouth. The 9.3 x 62 has a bore of .366". As the mouth on the 9.3 is shorter than the end of the neck on the .338-06 chamber, then surely part of the free-bore on the 9.3 will be .369 or .370 instead of .366" if you don't set the barrel back?

Odd, my AI case in the Mauser action required modification to the rails and the feed ramp. While my 700 did not. Further my pre-64 Brown Whelen would have required the same modifications as the Mauser. After setting the barrel back and chambered in 35 Whelen it fed fine.

The 30-30 case does benefit from the AI process as it does add more than 10% to overall case capacity, the squaring of the case reduces bolt head thrust. Case trimming, a pain in a regular 30-30 case is happily reduced greatly.

Riflehunter,

The standard throat ("freebore") of the 9.3x62 is a taper over an inch long, starting at .369 just in front of the mouth. A lot of old smokeless rifle cartridges had similar throats, to accommodate the shanks of the long, heavy round-nosed bullets used in those days.

The difference in case length between the .338-06 and 9.3x62 is .053", basically 1/20th of an inch. So yeah, depending on the original .338-06 chamber, there could be a very slight about of "enlargement" of the 9.3x62's very long throat just in front of the chamber--but I doubt it would make enough difference in accuracy to take the extra step of setting the barrel back a thread.

As long as the reduction in case taper doesn’t impair feeding, Go for it .
Moving the shoulder forward is also a possibility, as these case headspaces on the rim. Notwithstanding Feed n Function of course.

In the .303 British, reducing taper to the Epps / Ackley Improved doesn’t always work well with SMLE’s tapered box magazines.

The shoulder diameter expands from .441” to .454” , so yes virtually the same reduction in taper. After improving the point of the shoulder also moves forward.

The .280 Rem case has the point of the shoulder .050” further forward so it couldn’t be inadvertently chambered & fired in a 270 Win.
So slightly more volume to improve upon in a 280 Improved.

The Improvement starts from the point of contact at the neck shoulder junction.
That cone is larger than the standard case ( 17.5 degree, .441” diameter base ) , vice 40 degree .454” Ackley Improved.

Mo Bigga, Mo Betta !

I own a few AI’s: 280, 22-250, 375 Whelen, 375 H&H

My 22-250 AI, I think is worth it. Basically a 220 Swift in a better case (IMHO). It’s also one of my more accurate rifles < 1/2 MOA. It also shot 22-250 ammo in it accurately. When a fellow has a very accurate rifle to start with he likes the cartridge. Ask a certain writer what he thinks of a 270…

I like the 375 Whelen AI. There’s plenty of work making the brass at any rate. The dies were more available as was the reamer.

The others I have a luke-warm feeling. They are OK, but for me not worth the bother. Once done and cases formed they are probably “better”. But the 280 AI brass I’ve found is expensive and forming cost time and money. The H&H shoots the standard H&H ammo ok. I have no real need for the extra fps in the H&H and I don’t shoot it often enough to worry about stretching. I have not tried working up a load with standard 280 in the AI chamber.

All in all there are a few cases I think would benefit. They include 243, 30-30, 30-40, 303 Brit - I have all these and have not bothered “improving” them. Maybe if they were my main rifles I might of.

B - Seems like magazine & feeding issues are as important as any velocity improvement. Especially in the rimmed cases.

Does your 375 H&H Improved equal Weatherby or Ruger 375 ?

My 375 Improved is a solid increase over H&H and runs on peer with Wby numbers.

The Weatherby case will chamber in the 375H&H AI. Weatherby rifles are often free bored, so it’s pretty close.
The Ruger is pretty close too - going by memory - I think the Ruger may have a little larger capacity. All in all maybe 100 fps max between any of them.

I was looking for a 375 H&H when I came across this Pre-64 Model 70 chambered in the AI version. The rifle is pristine otherwise and would have brought much more money if the chamber hadn’t been messed with. I have quick detachable Leupold bases and rings along with a Pre-64 300 H&H set up identically with one spare scope and rings that will fit either. I was thinking at the time that I might still be able to safari with these rifles. I’m guessing now if I safari that might be in Texas at an exotic game ranch.

Fooled around with a .375 Weatherby some years ago, built by Dave Gentry--which is very similar to the .375 H&H AI.

Most of the "extra" velocity (once again) comes from higher pressure, not the relatively small amount of extra powder room. And it also comes at the "price" of extra recoil--when hundreds of thousands of hunters over more than 100 years have found the .375 H&H quite adequate.

I am not against new cartridges, and in fact have become quite fond of many, including the 6.5 PRC. But if I want to step up from .375 H&H performance would go to a larger caliber, say a .416 with 400-grain bullets.

What game, and build would this 416 target ?

Alaska or Africa

Rigby , or Ruger ? Or …

I looked at a BRNO 602 recently with an eye towards a LR 26” 338 Lapua ,
or 300 Norma build

416 takeoff barrel + 602 stock could be available.

I would have been happy with the 375 H&H too. I don’t try for maximum velocity, I like it when the holes in the paper come together, more so than big numbers on the chronograph.
My Ruger 416 Rigby gave me recoil head aches and right away! Granted I only tried 400 grain solids and they were full loads for a Rigby. I had thought about shooting cast bullets in that Ruger, but I decided to let it go instead. I toy with the idea of a 416 Remington or Taylor. My cousin has a 416 Remington - I’ll shoot it before I buy one.
But to tell the truth that 375 H&H AI is likely a more potent cartridge than what I’ll ever need.
I had a standard 375 H&H that evidently didn’t fit me well as felt recoil was greater than my Winchester, so I let that go I’ll probably have that on my estate sale unless one of my kids want it.

I seem to be the main person to be whining about poorly fit stocks…