Thoughts on Ackley Improved cartrages


PDA






Kachok
February 6, 2012, 07:53 PM
This is one thing that has intrested me for a while now, but I have never tried it one, what are your oppinions on AI cartrages, are they really better then the original versions of their respective cases.
Here are the claimed benafits of AI cartrages
Slightly improved case volume. Improved speeds as a result
Better combustion properties as a result of the sharp shoulder. Often claimed to improve accuracy.
Less case stretch for handloaders, longer case life as a result.
Are these all true, and if the AI versions can do all of this without any downsides why are they not factory chamberd (other then the 280 AI)

For those that don't know what I am talking about, an AI cartrage has had it's shoulder blown out to a 40 degree angle instead of the normal 17 degree found on the 06 based cases and 20 degree on the 308 based cases.

If you enjoyed reading about "Thoughts on Ackley Improved cartrages" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!
Mike1234567
February 6, 2012, 08:08 PM
Added to my subscriptions...

LoonWulf
February 6, 2012, 08:12 PM
dont forget less bolt thrust as the cartridge tends to grab the chamber walls harder since there is little to no taper. Ive hear that to be one of the reasons people end up with super high pressure when working with AI style cartridges, they dont get a sticky bolt LOL. Anyway, i still havent gotten my hands on one yet, if been thinking about doing a .30 gibbs in my 1903, and a 260 AI on my savage .243 when its barrel dies.

Kachok
February 6, 2012, 08:15 PM
I am dreaming up a 25-06 AI or 6.5-06AI build on a Savage action. Super flat trajectory, moderate recoil and can form from common brass.

Gordon
February 6, 2012, 08:35 PM
I believe most Ackley Cartridges used a 30 degree shoulder. Most Ackley cartridges are fireformable with factory ammo, hence "Improved" . The Gibbs not so, I was very disappointed that .270 and .30 Gibbs you could NOT safely fire form factory ammo so that was the deal breaker. 40 degree shoulders are pretty extreme and only used on some wildcats I think.

Hocka Louis
February 6, 2012, 08:37 PM
.30-06 AI is my .308 Magnum.

Kachok
February 6, 2012, 08:37 PM
I believe most Ackley Cartridges used a 30 degree shoulder. Most Ackley cartridges are fireformable with factory ammo, hence "Improved" . The Gibbs not so, I was very disappointed that .270 and .30 Gibbs you could NOT safely fire form factory ammo so that was the deal breaker. 40 degree shoulders are pretty extreme and only used on some wildcats I think.
No all AI cartrages are 40 degree. All of them I have ever seen anyway.

Gordon
February 6, 2012, 08:45 PM
Actually yes some, maybe most are 40 and prolly the ones you are interested in, but Parker came to settle on 30-35 degrees as being "better" in his later years and mine have that angle.

Kachok
February 6, 2012, 08:54 PM
Mabey the 35 degree shoulders are better, but whenever I look up the specs on any AI cartrage it is always listed as a 40 degree. That has always been their trademark.

helotaxi
February 6, 2012, 09:06 PM
Some have feeding issues. Not the best suited to semi-autos as a result. There are plenty of newer cartridges built on the improved model such as the SAUMs, WSMs and RUMs as well as the .204 Ruger.

Not all AI cartridges are a marked improvement in ballistic performance. The .243 is a perfect example. There are still plenty of .243AIs out there. Most guys cite the lack of case stretch as the reason.

Others provide a significant improvement over the standard cartridge. These are usually cartridges with a lot of case taper and/or a very shallow shoulder. The .257 Roberts and 22-250 are excellent examples of this.

Kachok
February 6, 2012, 09:16 PM
Who said the 243 AI was not higher performance then the regular 243? All information I can find on it show it runs neck and neck with the 6mm rem, about 100fps increase across the board. Never did load development on one but that is what I read. I would not expect a 40 degree shoulder to feed as smoothly as a 17 degree in a semi auto. In bolt guns it is not likley to make a notable difference.

35 Whelen
February 6, 2012, 09:23 PM
I own a 257 AI and like all the original AI cartridges, it has a 40° shoulder. It netted 200 -250 fps over the standard 257 Roberts, but then again the 257 Roberts is loaded to WAY low pressures(45,000 CUP) for some reason.
John Barsness of Handloader magazine claims improved cartridges really don't gain you that much performance. Realistically, I'd say blowing out a .308 based, *X57 or an '06 case would gain you 100 fps, maybe a touch more. Can't comment on the other stuff but it sounds like someone rationalizing an AI chambering which is certainly OK!

35W

Kachok
February 6, 2012, 09:43 PM
100fps seems to be the going rate, 280 AI maxes out a 150gr pill 100fps faster then the 280 Rem, the 30-06 AI can push a 180gr 100fps faster then a regular 06, though the difference grows a bit more with 200-220gr bullets. The 25-06 AI is the only one that seems to bump it up a little further in the 150-200fps range, but that might just be because people who tweek that round seem to like 26" tubes.
It is worth mentioning that the 280AI pushes very close to 7mm rem mag performance in a smaller package burning several grains less powder, and the 25-06 AI matches the 257 WBY with alot less powder (about 8-10gr avarage)

35 Whelen
February 6, 2012, 09:56 PM
It is worth mentioning that the 280AI pushes very close to 7mm rem mag performance in a smaller package burning several grains less powder...

Funny you mention that. I have an old Ruger 77 that was a 7x57 that Dad had rechambered to 280 Remington. For nigh on 15 years I've only fired two loads out of it; a 140 gr. Partition at a shade over 3000 fps, or about par, and a 160 gr. Partition at a (small) shade UNDER 3000 fps. Don't ask me how...I just owkred up the load and stopped when groups were 1" or less and velocity was acceptable.

35W

Kachok
February 6, 2012, 10:06 PM
That is a bit over the published max load for a 280 rem, the AI maxes out a 160gr at about 3050 fps, every bit as fast as the 7mm WSM that would make for one very dead elk for sure. I don't have any elk down here, so I am looking to make a super flat shooting deer rifle, that is why I am looking into the 25-06AI or 6.5-06AI both should push a 115-120gr bullet to around 3400fps with a custom 26" barrel.

nastynatesfish
February 6, 2012, 10:13 PM
i have a buddy that has a 2506ai and has had nothing but grief with it. from loading to spit necks with new brass. dont know what he ever got figured out with it. im still waiting on a 7mm ai mag to show up.

Kachok
February 6, 2012, 10:22 PM
Some calibers seem to take to AI very well and others do not. You see alot of 25-06AI and 280AI but how many 270 AI rifles have you seen.......me neither. Never seen a 300 WM AI or 7mm RM AI either. I would think you could make one easy enough. Can you machine a factory barrel to make an AI or would you have to get an aftermarket barrel?

Cemetery21
February 6, 2012, 10:32 PM
223AI feeds fine in ARs I have 3 that get quite a bit of mileage on prairie dog trips and feed as well as 223s. I went to AI for just a little more speed and less trimming. I'm just 3 years/loading cycles into it, so not sure how long they will go before trimming. They actually get shorter on fireforming because the taper and shoulders are blown out.

Edit to answer - mine were cut on 223 chambers. All are custom built from match barrel blanks, but two were shot as 223 before they were reamed out to AI. 223 headspaces correctly in the AI chambers. You lose a little speed in fireforming, but in my case, the accuracy was still there so I could hunt and fireform at the same time.

Clark
February 7, 2012, 12:03 AM
223 is SAAMI registered at 55kpsi, so all the published loads and all the commercial ammo is wimpy.

The case head is good for 75kpsi with long brass life.

The real advantage of Ackley Improved in 223 is almost not measurable, but important gains are from higher pressure.

The 270 is registered at 65kpsi and the case head is good for 67kpsi with long brass life. You will never hear of anyone claiming more velocity with 270 Ackley improved.

I can get 3900 fps with 75 gr in 257 Roberts Ackley Improved, but I can only get 3600 with long brass life.

There is a sucker born every day, and out of control variables are often the key.

Kachok
February 7, 2012, 12:45 AM
I don't know if I quite agree with that, some magnums have a lower max chamber pressure then their standard counterpart, but they are still faster because they can use more of a slower burning powder. Lower peak pressure, but maintains good pressure through more of the barrel. If it were all about peak pressure case volume would mean almost nothing.

hang fire
February 7, 2012, 02:07 AM
Decades ago I had a .257 Ackley improved, it was a great deer slayer.

I also had a .35 Gibbs which was a good moose thumper, but when sighting in that light rifle, I thought it tried to kill on both ends.

Clark
February 7, 2012, 02:47 AM
223 Ackley at 55kpsi will push a 40 gr bullet 50 fps faster than 223 at 55kpsi.
223 Rem at 75kpsi will push a 40 gr 300 fps faster than 223 Rem at 55kpsi.
223 Ackley at 75kpsi will push a 40 gr 350 fps faster than 223 Rem at 55kpsi.

Conflation occurs when the identities of two or more individuals, concepts, or places, sharing some characteristics of one another, become confused until there seems to be only a single identity — the differences appear to become lost.

Case capacity increase from Ackley improving a chamber would be an independent variable.
Velocity would be a dependent variable.
Peak pressure would be another independent variable.
If we measure the effect of case capacity increase on velocity, but do not control [have unknown change in] peak pressure, then we have an out of control variable.

Out of control variables have been associated with bad science, cheating, and having a screw loose.

Cosmoline
February 7, 2012, 03:41 AM
AI's are a great way of getting a little more power out of a rifle you already have. In the good old days, folks didn't have the kind of spending money (or credit cards) we take for granted now. So ditching your .30-30 for a .308 wasn't always an option. Plus the selection was far more limited. The AI's are a simple, cost-effective upgrade that can be done by a smith quickly. You don't change brass or bullets, you just fire form (at least with the ones I'm aware of).

Nowadays though people wanting to upgrade are more likely to ditch the old rifle and buy a new one. The AI's are the province of handloading nuts ;-)

Kachok
February 7, 2012, 09:45 AM
Well I am one of those handloading nuts :) So they should be right up my alley. I want a long range shooter, something with a little more speed to use where my 6.5x55 would fall off trajectory wise. 25-06AI can push scarry speeds with really good trajectorys, it has "enough" downrange energy but not much more. 6.5-06AI can use everything fron light 120gr bullets at similar speeds and ultra high BC 140gr VLDs at just over 3k to resist wind drift and hit hard 500 yards out. 280 AI is a well known Ackley it is not quite as good at light projectiles but can sling 160-168gr bullets around 3kfps giving it best in class downrange energy, probably more power then I need but I would love to have one anyway.

Kachok
February 7, 2012, 07:50 PM
Just bought a Savage 110 (30-06) to be a parent action, looking into barrel options to try a wildcat. Of course if it ends up shooting as well as my mkII I will have a hard time taking the 06 barrel off :D

greyling22
February 7, 2012, 08:11 PM
I've got a 257Ai. it's great. I don't know how it actually compares to a roberts, but on paper it's supposed to net another 200fps and be one of the better ackley conversions.

helotaxi
February 7, 2012, 08:34 PM
223 Rem at 75kpsi
Is essentially a proof load...

SAAMI pressure for the .223 is currently expressed in CUP but roughly translates to ~63kpsi. 75kpsi is a 20% overpressure load and 10kpsi over the max that SAAMI considers safe for ANY load.

I think that I understand your basic premise though. Many of the claims for significant velocity increases come from the fact that that loads are well outside safe pressure levels, not because of an, often very modest, increase in case capacity. The basic danger of wildcatting is the lack of pressure tested load data. You're often on your own.

Chedderbob
February 7, 2012, 08:38 PM
Seeing as how I am constantly buying, selling, and trading firearms (looked down upon on this particular board, but hey, the truth is the truth!), I avoid AI cartridges like my ex-wife.

There is a fella on a local gun trading board I frequent that has been hawking a savage .270 AI for months with no takers (price ain't to terrible either.) If you like marginal gains over common cartridges, forming your own brass, and being stuck with a gun for your entire life, the. AI is for you.

I generally find that there is nothing an AI cartridge can do that a commercially available cartridge can't do. Again, to each his own.

MachIVshooter
February 7, 2012, 08:59 PM
Not all AI cartridges are a marked improvement in ballistic performance. The .243 is a perfect example. There are still plenty of .243AIs out there. Most guys cite the lack of case stretch as the reason.

Others provide a significant improvement over the standard cartridge. These are usually cartridges with a lot of case taper and/or a very shallow shoulder. The .257 Roberts and 22-250 are excellent examples of this.

This.

I wouldn't bother imrpoving a case that already has a fairly sharp shoulder and little body taper (.308 based cartridges, .222/.223/.222 RM). But those based on the 250 Savage, the Mauser cases (6mm rem, .257 Bob, etc.) and the '06 family seem to benefit noticeably.

I'll probably improve my .25-06 at some point. My 6mm-06 build is going to be AI. I would love to have a Kimber 84L Classic Select in .280 AI.

If you like marginal gains over common cartridges, forming your own brass, and being stuck with a gun for your entire life, the. AI is for you.

That's the thing with AI, though......your brass is formed by shooting the standard factory load in your rifle. The only expense is AI dies. It's not really a wildcat; You can still shoot ANY factory ammo in your AI chamber.

Resale? If the prospective buyer is a handloader, he'll probably appreciate it. If he is not, well, he'll just be throwing his brass away, so it doesn't matter if it's fireformed to the AI chamber. The non-handloader will still have a perfectly good rifle, he'll just never realize the benefits of the AI.

Zor
February 7, 2012, 09:03 PM
http://www.riflemagazine.com/magazine/article.cfm?magid=7&tocid=38

I'm just about set on the 257 AI for my first build from the action up. I went to my LGS and talked with one of the fellas there about it. He said the most improved round was to the 30-30, that is until the lever revolution ammo came out. He also agreed that the 257 AI was one of his better successes. Read the article I linked and you'll see that not everything Ackley tried was a success. He admitted to that.

However, I still haven't shot one, so take my word with a grain of salt.

Zor

MachIVshooter
February 7, 2012, 09:15 PM
I'm just about set on the 257 AI for my first build from the action up.

.257 AI is a great round, but IMO, doesn't make a lot of sense if you don't already have the .257 rifle. The cartridge is too long to fit in a short action, and the AI version of the .257 bob still won't match the performance of unimproved .25-06. Might as well just buy a .25-06.

Kachok
February 7, 2012, 09:20 PM
As much as I like the 257 I already have the perfect close-medium range deer rifle (6.5x55) I would be looking for extended range and performance.

Zor
February 8, 2012, 12:22 AM
.257 AI is a great round, but IMO, doesn't make a lot of sense if you don't already have the .257 rifle. The cartridge is too long to fit in a short action, and the AI version of the .257 bob still won't match the performance of unimproved .25-06. Might as well just buy a .25-06.
I'm going with the improved bob for a list of reasons. It fits in the intermediate action Mausers (6.5 swede and 7x57), it's an oddball (which I like), and for the sake of curiosity. Sierra has loads listed for it and claims that it outperforms the 25-06 right in their manual. I have a rifle that chucks bigger bullets at fast velocities for big game, this rifle is for smaller stuff like antelope, javelina and whitetail. Also, I'm building the rifle so the cost is going to be pretty much the same no matter what the chamber is.

MachIVshooter
February 8, 2012, 02:33 AM
It fits in the intermediate action Mausers (6.5 swede and 7x57)

If you're building on a small ring Mauser action, that's a little different story. I just hadn't assumed so, since very few people do. I like the small rings, though already having a .25-06, I'd just stick with the 7x57 (maybe improve it).

But for the record, the improved bob cannot match the standard .25-06.

Sierra has loads listed for it and claims that it outperforms the 25-06 right in their manual

5th edition Sierra's top load for the .257 Roberts AI is 2,900 FPS with 117/120 gr. pills. The unimproved .25-06 is listed for 3,100 FPS with those weights, and I've driven them a full 100 FPS faster than that in my 24" Remington 700 BDL with no overpressure signs. Both test guns in the Sierra manual were Savage 12VSS with 26" barrels, so there's no discrepancy there.

The "far more efficient" wording in the book is also self-contradictory; With the 117/120 gr. bullets, There are two common powders listed for both calibers at the 2,900 FPS mark. IMR4831 Charge in the Bob AI for 2,900 is 46.4 grs; To get 2,900 in the .25-06 unimproved with IMR 4831, they show a charge of 44.9 grs. With IMR 4350, the charges are exactly the same. Oops.

I'm not saying there's anything wrong with the Roberts. It's a good round. But the .25-06's equal it is not, improved or otherwise.

35 Whelen
February 8, 2012, 06:20 AM
The "far more efficient" wording in the book is also self-contradictory; With the 117/120 gr. bullets, There are two common powders listed for both calibers at the 2,900 FPS mark. IMR4831 Charge in the Bob AI for 2,900 is 46.4 grs; To get 2,900 in the .25-06 unimproved with IMR 4831, they show a charge of 44.9 grs. With IMR 4350, the charges are exactly the same. Oops.

Not contradictory in the least. In fact you unknowingly contradicted yourself. All things equal, a particular cartridge case cannot obtain more velocity with less powder than a smaller case of the same caliber. It's simple physics. Think about it: the 25-06 case has more internal capacity than the 257 AI, that is a given. Therefore, it will require more of the same powder to propel a given bullet a velocity the same as that obtained by the 257 AI with the same powder and bullet.

Your quoted load from the Sierra manual was either misread or is a gross misprint. I'd bet the farm that the 25-06 load should read 49.4. Consult the Hodgdon on-line manual and I think you'll see what I'm talking about.

All I have handy is an old 80's vintage Speer #9 manual, but it has both cartridges and generally speaking, the 25-06 has about a 100 fps advantage over the 257 AI.

So in the real world: From a velocity/energy standpoint, that gives the 25-06 less than a 50 yd. advantage and from a trajectory standpoint, less than 1/2" at 400 yds.

Pick your cartridge, no animal's going to know the difference.

35W

RevGeo
February 8, 2012, 09:27 AM
I have two AIs. The rifle barrel on my drilling is .22 Sav HiPower AI. It shoots a 70gr .228 bullet at about 3400 fps using H380. Powerful antelope and whitetail medicine, but kind of messy.
The other is a sporterized Original Haenel Lorenz Wehmanns Gewehr single-shot 98 Mauser chambered for 30-40 AI but requires a .315 bullet because it was originally chambered for 8.15x46R which is about like a 32-40, power wise. I have a bullet forming die to squeeze .323 (8mm) bullets down to .315.To form cases I shove regular 30-40 cases over the expander ball in the sizing die and seat a .315 bullet over a standard Krag load. That gives me 'factory ammo'. Never had a problem fire forming cases in either gun,BTW.
Parker Ackley (who did the rechambering on both of these rifles for my late father) claims .300 H&H velocities from this cartridge but his loads of 4350 look pretty hot to me. I load it to 30-06 levels using H380 with no problems.

Some of the loads in Ackley's book would have the lawyers sharpening their pencils these days, I'm thinkin', but apparently he had no problems with them.
For anyone unfamiliar with Ackley's books his Handbook For Shooters And Reloaders has a fascinating chapter on his attempts to blow up various military surplus actions with rediculous loads. The results are rather surprising.

pcf
February 8, 2012, 09:59 AM
I've had one AI, it was a superb Cooper 52 in .280 AI, that I foolishly let it go for a 7mm STW in a misguided quest for more velocity.

Speaking in very general terms, with a 150gr bullet, I was using 3-4 grains more powder in the 280 AI over the 280 Rem and gaining 150-200 fps. I was using 21-24 grains more powder in the 7mm STW over the .280 AI and picking up another 200-250fps.

IMO the .280 AI nears peak efficiency in a 7mm. There are cartridges that can beat it's performance, but it comes with disproportionate increases in powder and recoil.

Kachok
February 8, 2012, 10:49 AM
Yeah i like speed and all but I would never trade a 280 Ackey for a massivly overbore 7mm STW. The 06AI case seems to be just right for 6.5-7mm bore, nobody fussing about rapid barrel burn, no excessive recoil, but they are nipping at the heals of hot belted magnums.

Zor
February 8, 2012, 12:53 PM
Does anyone have pressure data that they could add to the discussion? Did any of the manufacturers pressure test loads and put out data on AI vs standard?

Kachok
February 8, 2012, 01:03 PM
Nosler #6 has load data for the 280AI and 30-06AI but no pressures given.

Zor
February 8, 2012, 01:23 PM
Sierra gives load data for some of the A.I.'s as well, but I can't find pressures. Does anyone have one of Ackley's books?

LoonWulf
February 8, 2012, 01:30 PM
Hodgdons site has pressure data with their load info.
They do not have the 6.5-06AI, just the stanadard. Top velocity with 140s is in the high 28s pressure running about 63K.
.280 AI shows about 2850ish with 160/62s at 60-62k, bout 3k with 140s.
06AI they dont list....odd that, of all the AIs i thought they would have...

pcf
February 8, 2012, 01:35 PM
Hodgdon data center http://data.hodgdon.com/main_menu.asp has some info on the 280 AI with pressure.

MachIVshooter
February 8, 2012, 02:35 PM
In fact you unknowingly contradicted yourself.

Not hardly. He cited the Sierra manual, I referenced it.

http://i110.photobucket.com/albums/n117/Hunter2506/101_1270.jpg

Your quoted load from the Sierra manual was either misread or is a gross misprint. I'd bet the farm that the 25-06 load should read 49.4.

They list 50.9 for 3,100 FPS, and I have real world data to back the numbers up. My go-to load is 54.0 Grs. 4831 with 117 Sierra Gamekings, and it averages 3,195 FPS over my Chrony Gamma Master at 15', with a high of 3,227 FPS and a low of 3,166 FPS. And remember, my 700 BDL is a 24", not the 26" Sierra used for both the .257 AI and .25-06.

Speer #13 also shows 45.0 Grs. IMR4831 to get 2,793 FPS from the unimproved Roberts (Speer doesn't have AI data) from a 24" Ruger M77, and 46.0 Grs. 4831 in the .25-06 (700 BDL 24") to get 2,769 FPS. With IMR4350, Speer shows the Roberts at 43.0 Grs. for 2,758 FPS and the .25-06 at 44.5 for 2,773 FPS. Again, both 24" barrels, and this is the unimproved Roberts case, so it should have slightly better efficiency than the improved.

I'm in agreement with you that, as a rule, smaller cases are more efficient with a given charge weight. But there is also a phenomenon that can occur when some cartridges are at the top end of their capacity where efficiency actually decreases. I can't explain it, but I've witnessed in with handgun cartridges using certain powders and loading over max published data. Kinda like a Bullet's BC rating usually increases with velocity, but sometimes it falls off.

The Roberts does maintain higher efficiency with lighter bullet weights, and when you load below it's maximum. Not by a lot (3-6 grains for the most part), but it is.


Pick your cartridge, no animal's going to know the difference.

I'm in agreement there. I'm not disputing that the .257 AI is a perfectly capable cartridge. Just pointing out that it ranges from slightly more efficient to no more efficient than the .25-06, and cannot match the ballistics.

Think of it like this; Chevy small block V8 - You have a 350 (roberts) and a 400 (.25-06). You can turn that 350 into a 383 stroker and it'll make more power than it did at 350 CI, but it's still not a 400. And at best, there'll be a hair's breadth difference in fuel economy. In fact, larger, more powerful engines are often more efficient in heavy vehicles or when towing, Just as sometimes the larger cartridge case is more efficient with the heaviest loads.

c.latrans
February 8, 2012, 02:54 PM
They are fun to tinker with. 20 years ago I thought the AI concept was brilliant, and still believe it has its advantages in certain areas. I have built several AI guns over the years, but probably wont bother with another. I still have a .25-06 AI that will honestly run on the heels of a .257 Wby. Age has changed my attitude about many things, including this issue. If I need more than, say, a standard .30-06 offers I will simply step up to a .300 mag of some version. Trying to get more out of a cartridge than it was designed to provide seems to me, at this point in my life, to be a really good way to bring grief I dont need.

I have never had a blow up with an AI, but I have seen pressure issues such as significant bolt face extrusion and primer pockets that opened up WAY faster than normal, so it seems intuitive that the pressures can get up there.

Clark
February 8, 2012, 03:02 PM
The 257 Roberts, 257 Roberts Ackley Improved, and 25-06, all use the 1889 Mauser 7.65x53mm case head built with large Boxer primer pocket.
That case head is good for 67kpsi and long brass life for an individual rifle in all three rifles.
For those who do not use load books, that makes all three very similar.

I built a few 257 Roberts Ackley Improved rifles on VZ24 actions 10 years ago.
The first one I headspaced like a 257 Roberts.
That is a mistake.
It should be .004" tighter, so that when the firing pin pushes the case forward, it is already crushed into the sharp chamber shoulder. Otherwise, it crushes .004" into the sharp edge, expands, grabs the walls, and then stretches back. That long stretch can crack the brass. In that rifle, 10 years later, I still fire form with Cream of Wheat to get some shoulder for the the firing pin to work against.

Look at the good groups at 100 meters!

RevGeo
February 8, 2012, 06:19 PM
I have Ackley's Handbook For Shooters And Reloaders and he doesn't list pressures with his loading data.

35 Whelen
February 8, 2012, 09:06 PM
The "far more efficient" wording in the book is also self-contradictory; With the 117/120 gr. bullets, There are two common powders listed for both calibers at the 2,900 FPS mark. IMR4831 Charge in the Bob AI for 2,900 is 46.4 grs; To get 2,900 in the .25-06 unimproved with IMR 4831, they show a charge of 44.9 grs. With IMR 4350, the charges are exactly the same. Oops.

True, the 25-06 is slightly more efficient with IMR-4350, IMR-4831 and other relatively slow burning powders in that particular manual. My old Speer manual used exactly the same powder in both the 257AI and the 25-06. Even counting the IMR4350 and 4831 the 257AI is uses quite a bit less powder than the 25-06, but this is especially true with powders with a faster burning rate than 4350 and 4831.

I almost bought what you showed in the picture of the Sierra manual, but there's one small detail that causes me to question Sierra's data (and nothing against Sierra..I have two of their manuals).
Under the 25-06 data, if you'll look close at the charges for IMR-4350 and IMR-4831 you'll notice that Sierra show almost identical charges of each of these powders for the same velocity (2800-2900 fps range)with the same bullet. :confused:

35W

MachIVshooter
February 8, 2012, 09:33 PM
I almost bought what you showed in the picture of the Sierra manual, but there's one small detail that causes me to question Sierra's data (and nothing against Sierra..I have two of their manuals).
Under the 25-06 data, if you'll look close at the charges for IMR-4350 and IMR-4831 you'll notice that Sierra show almost identical charges of each of these powders for the same velocity (2800-2900 fps range)with the same bullet.

Yeah. Why does that make you skeptical? 4350 and 4831 are both medium-slow powders.

#137 & #146:

http://www.reloadbench.com/burn.html

Those are two of my most-used powders from 6mm Rem to .375 Ultra Mag, and they do tend to require very similar charge weights in a given cartridge.

35 Whelen
February 8, 2012, 10:09 PM
Yeah. Why does that make you skeptical? 4350 and 4831 are both medium-slow powders

It makes me skeptical because they're similar only in that they're relatively slow burning powders, but not even remotely the same as the Sierra data would imply.
If you still don't understand this, work up a 120 gr. load in your 25-06 using identical charges and see which one begins to show pressure first, it'll be the 4350, I assure you. Then stop and continue on with the other, which will be the 4831, and make a note of how much more 4831 can be loaded before pressure signs appear.
If you're serious and you really don't understand this, you might want to get some different manuals and do some studying.

I've used both of these powders for around 20 years in the same 280 Rem. In fact I use identical charges (55.5 grs.) with both powders. The difference is I use 4350 with a 140 gr. bullet and and 4831 with a 160 gr. bullet. Were I to assume they were very similar powders and us said charge of 4350 under a 160 gr. bullet, I'd be pounding the bolt of my rifle open with a rubber mallet because it'd be a good 1.5 - 2.0 grs. over maximum.

See what I mean?

35W

MachIVshooter
February 8, 2012, 10:20 PM
not even remotely the same as the Sierra data would imply.

Some random selections from Speer #13 (all max loads)

.300 H&H mag 165 gr.
IMR4831 71.0 Grs. 3185 FPS
IMR4350 69.0 Grs. 3185 FPS

7mm Rem Mag 175 gr.
IMR4831 59.0 Grs. 2,827 FPS
IMR4350 56.0 Grs. 2,789 FPS

.243 Win. 90 gr.
IMR4831 47.0 Grs. 3,107 FPS
IMR4350 46.0 Grs. 3,026 FPS

8x57 Mauser 200 gr.
IMR4831 54.0 Grs. 2,395 FPS
IMR4350 53.0 Grs. 2,432 FPS

I get what you're trying to say, and yes, 4350 is a little faster powder. Still, load data tends to be very close between the two, almost interchangeable with some cartridges/bullet weights.

I've run very heavy charges of both (think 97 grs. 4350 in my .375 RUM behind a 250 gr. BTSP and 99 grs. 4831 behind a 260 ballistic tip in the same), often exceeding published velocities in shorter barrels. Never had pressure issues beyond slightly flattened primers with either powder.

BTW, there is also a 2,900 FPS 300 gr. load for the RUM with either powder. 95.6 Grs. 4831, 93.5 Grs. 4350

capreppy
February 9, 2012, 09:02 PM
I've been giving this a lot of reading of late. I'm looking to rebarrel my Stevens 200 in .270 Win to either a .308 Win or a .260 Rem, but have been reading a fair amount regarding the .260AI. The .260AI has a lot of things going for it. You can fire regular .260 Rem brass in an AI chamber to fire form it and I like that.

MachIVshooter
February 10, 2012, 01:27 AM
I've been giving this a lot of reading of late. I'm looking to rebarrel my Stevens 200 in .270 Win to either a .308 Win or a .260 Rem, but have been reading a fair amount regarding the .260AI. The .260AI has a lot of things going for it. You can fire regular .260 Rem brass in an AI chamber to fire form it and I like that.

.260, like other .308 based cartridges, doesn't benefit much from improving. They already have minimal body taper and fairly sharp shoulders.

.308 vs. .308 AI:

http://www.bellmtcs.com/store/images/category157/300Savage9_3-vi.jpg

Why not improve the .270 you already have? Or, since you're already working with a long action, do a 6.5-06 AI.........It'll out-perform the .260 by quite a bit.

GooseGestapo
February 10, 2012, 03:21 PM
All the discussion of the AI is nice, but remember, you're talking apples vs. oranges when comparing two different rifles, barrels, and lot#'s of powders.

All this makes a "ballistics manual" data comparison moot.

I've got a standard .257Roberts with the so called "3inch" chamber. For practical purposes it's data mirrors that of the .257Roberts RCBS "Improved" data that one of the manuals had data for back in the '80's when I built the rifle. It is an example of "one". A rule unto itself.

I had a .22Hornet AI back in the early '80's. It was a useless piece of junk as the chamber had been cut poorly rendering the rifle useless except for one shot with factory ammo. Fireformed brass was useless as it would split and collapse when sized. The chamber was cut too deeply and was out of round......

With the cost of new barrels plus cost of installation by a "qualified" gunsmith, I would just get a "used" Weatherby in either .257Wby (what I've got) or a .270wby if wanting something a little bigger. A used Weatherby Vanguard can be had for less than the cost of a new barrel on a Savage. (maybe even a new Vanguard for cost of a match grade barrel....).
Plus, you add the substantial cost of a set of dies for the new chamber, which can exceed $200.00, you can see that you could almost get a "magnum" rifle and buy a near lifetime supply of components for the cost of an "Ackley Improved".

I could see getting something like a .280AI that's a SAAMI listed cartridge in a new rifle, and reasonable priced dies, ect. But, I got a "deal" on a new, unfired .30 Herret barrel for a T/C Contender for $75.00. Then I found that a set of dies would set me back $200.00..... It's still unfired !!! I may have it reamed to .30/30 or such. Or just sell it to get my money back......
Don't even get me started on lot to lot variation on powders...... or barrels cut with different reamers....

If you are a gunsmith and can do the work yourself, including machining the dies like P.O.Ackley, then they make great experimental pieces... But if not, you'll be better off just getting a E.A.Brown barrel for your Savage action in the standard 6.5/06, and use an extra 2" bbl length to get the "extra" speed you "think" you need.
just my honest opinion... That, and I wouldn't use the Savage action as it lacks the "camming" of a Mauser, Rem. M700, or Win. Mod-70 to extract the case. Even getting "close" to peak operating pressures with the Savages I've had (.243 -(2), .30/06LH, .300RemUltMag) and extraction gets difficult due "stickiness" of the brass and at max loads needs a wooden block to extract the brass....

Plus that, and the fact that with Reloader 25 from my .257wby I'm seeing 3,700+fps with Max 100gr loads, and 3,650fps with a 2% reduction to a "working" load, that I can reload 5x+, and this from reformed 7mmRemMag cases that cost me nothing; I've got a $400 (including dies, scope) rig that I can get my money back on if needed..... With a AI, you're probably "stuck" with it.....Including the very expensive custom dies....

Several years back I got the hankering for something a little speedier. I got a used Savage M110 in .300RUM for $250 at a pawn shop because no one wanted it due to $$$ ammo. With some milsurp powders, I'm shooting it (what little I shoot it) for less than the cost of new components in a .30/30. Then I stumbled across the .257wby. Having a near lifetime supply of .257" bullets on hand and "all that surplus powder", I too picked up the .257 for $250.00......

Now, my desire for "something" faster has been assuaged, and I even "occasionally" hunt with them. Amazing though, that all the deer I've shot with them have been under 200yds (except one with the .300RUM @ 325yds... but still a "chip shot" for the '06....).
Even the little .257Robt. would have been"point blank" for that shot..... Hence it get's shot and hunted much, much more......

quartermaster
February 12, 2012, 10:26 AM
I am having a 25-06 AI rifle being built. It should be in my possesion within a month. I love the 25 cal, hence my handle on thr. I wanted to try the AIs due to all the reasons you mentioned in your initial post. I'm hoping to get almost 257 wby velocites out of it without dealing with all the freebore, which hopefully will make it easier to load for accuracy.

The new one is being built on a trued 700 action with an oversized recoil lug, Shilen 10" twist #5 SS 26" barrel, bedded in a laminated stock, and a Jewell trigger. It has a tight chamber, so I will be slightly turning necks. Hopefully the twist will be fast enough for 115-120 gr heads. Respectable authorities say it will be, although Shilen says I need a 9"

I am subscribing to this post to post my results, likes and dislikes when I get going on it.

I may start a thread, even though it has probably been beaten to death, on the fireforming process. I am hoping to be able to work up a load for it during that process, but who knows if it will be the optimum load for the second shooting. Part of me wants to try the fire forming process with the pistol powder and cream of wheat process and the other part of me wants to jam the bullets and shoot. I have 100 Norma brass to get started with, but can't decide which route to go. I'm leaning towards the latter.

Sorry to get off the original subject of this post Kachok. I am excited about getting this rifle and I guess it shows. If it works out I will consider another AI being made from an action of one of my other duplicate calibers.

helotaxi
February 12, 2012, 10:32 AM
Nice thing about an actual improved cartridge is that jamming into the lands isn't required to control headspace while fire-forming.

Coltdriver
February 12, 2012, 10:56 AM
In his day Parker Ackley was definitely on to something when he created the first improved rounds.

I have his books and they make for great reading.

And I have a .243AI.

But given the powder/bullet/chambering improvements we have seen in the last 10 years I wonder if there is any real advantage to an AI chambering? They do look cool.

I have my eye on a .270 WSM. Same sort of concept with the fat cartridge.

I have not found the very highest velocity loadings to be the most accurate also. Once in a great while that happens or you find a "node" up near the limit where it works out.

MachIVshooter
February 12, 2012, 11:00 AM
The new one is being built on a trued 700 action with an oversized recoil lug, Shilen 10" twist #5 SS 26" barrel, bedded in a laminated stock, and a Jewell trigger. It has a tight chamber, so I will be slightly turning necks. Hopefully the twist will be fast enough for 115-120 gr heads. Respectable authorities say it will be, although Shilen says I need a 9"

That should be quite a shooter! And 1:10" twist is standard for .25-06, so you shuld be fine unless you start making custom 130 gr. + pills.

SlamFire1
February 12, 2012, 11:26 AM
Don’t forget less bolt thrust as the cartridge tends to grab the chamber walls harder since there is little to no taper.
P.O Ackley was selling snake oil.

Cases don’t act as wedges or inclines. Unfortunately they stretch. They don’t carry load, or should not carry load, they are simply a gas seal.

At the time ole PO was selling his Ackley improved (AI) cartridges, he was blowing out the shoulders, straightening the case, to increase powder capacity and raising pressures. It is obvious that ole PO was taking flak from folks who were claiming that his high pressure cartridges were overstressing the action.

This would be an interesting side topic, but based on the cartridge taper advice found in my design books, straight cases are not an ideal form. They don’t steer well and they don’t retract well. If the mechanism does not cycle well, if case sticking is a constant problem, if feed geometry is too fickle, the mechanism will be a failure.

P.O Ackley cartridges are very interesting and P.O’s test of a straight sided cartridge holding pressure without a breech block has been duplicated. The tester swabbed the chamber out with alcohol swabs between shots. The Ackley cartridge held. However the other cartridges, such as the 30-30, 35 Remington, blew out of the breech at 1900 fps. A 150 grain cartridge case flying at 1900 fps will go through both sides of most people's skulls.

Ackley was taking heat because he was getting high velocities from his improved cartridges, cartridges which were being used in actions not designed for the things. P.O. wanted to show that his speedy cartridges did not increase bolt thrust, and infact as a result of his experiments, claimed they actually reduced bolt thrust. Which was bogus as heck as these improved cartridges actually ran at higher pressures. Higher pressures increases bolt thrust, it does not lessen it. P.O got higher velocities through higher pressures.

Read carefully Boatright’s papers one of which he shows how a 308 case, in a clean chamber, can lock in and hold pressures by itself up to 25K psia.

Go to Jim Boatright’s web page.

http://www.thewellguidedbullet.com/

Look for yielding of the brass case in these studies

http://www.thewellguidedbullet.com/mechanical_studies.htm

However once pressures go above 25K psia, Boatwright shows the brass case stretches and if not supported, the case head will blow off.

Regardless of taper, and all that mystical mojo, cases are made out of brass and will stretch. There may be bolt load reduction due to friction and stretching but it is inconsistent and not to be relied on in any way.

Apparently the standard 30-30 is strong enough not to lose its case head without the AI taper.

http://gunsmithtalk.wordpress.com/2008/08/19/ackley-bolt-thrust-tests/

I have not seen actual pressure test data verifying his claims of more velocity with less bolt thrust. If you notice, P.O. Ackley never conducted his test with a 30-06 or a similar high pressure cartridge. I am certain those would have blown right out the back of his lug less rifle. Ackley and others did not conduct sensitivity tests, varying chamber finish, (chrome for example), powders, primers, or much of anything else. I totally disagree with the implicit conclusion that Ackley and others have drawn, which is if Ackley improved cartridge reduces bolt thrust, a user can just pour the coal into the cartridge and let fly. Ole P.O. was interested in promoting his cartridges, found a “one off” and left a very misleading legacy in terms of case friction, load, and chamber roughness.

35 Whelen
February 12, 2012, 01:31 PM
P.O Ackley was selling snake oil.

Cases don’t act as wedges or inclines. Unfortunately they stretch. They don’t carry load, or should not carry load, they are simply a gas seal.

At the time ole PO was selling his Ackley improved (AI) cartridges, he was blowing out the shoulders, straightening the case, to increase powder capacity and raising pressures. It is obvious that ole PO was taking flak from folks who were claiming that his high pressure cartridges were overstressing the action.

This would be an interesting side topic, but based on the cartridge taper advice found in my design books, straight cases are not an ideal form. They don’t steer well and they don’t retract well. If the mechanism does not cycle well, if case sticking is a constant problem, if feed geometry is too fickle, the mechanism will be a failure.

P.O Ackley cartridges are very interesting and P.O’s test of a straight sided cartridge holding pressure without a breech block has been duplicated. The tester swabbed the chamber out with alcohol swabs between shots. The Ackley cartridge held. However the other cartridges, such as the 30-30, 35 Remington, blew out of the breech at 1900 fps. A 150 grain cartridge case flying at 1900 fps will go through both sides of most people's skulls.

Ackley was taking heat because he was getting high velocities from his improved cartridges, cartridges which were being used in actions not designed for the things. P.O. wanted to show that his speedy cartridges did not increase bolt thrust, and infact as a result of his experiments, claimed they actually reduced bolt thrust. Which was bogus as heck as these improved cartridges actually ran at higher pressures. Higher pressures increases bolt thrust, it does not lessen it. P.O got higher velocities through higher pressures.

Read carefully Boatright’s papers one of which he shows how a 308 case, in a clean chamber, can lock in and hold pressures by itself up to 25K psia.

Go to Jim Boatright’s web page.

http://www.thewellguidedbullet.com/

Look for yielding of the brass case in these studies

http://www.thewellguidedbullet.com/mechanical_studies.htm

However once pressures go above 25K psia, Boatwright shows the brass case stretches and if not supported, the case head will blow off.

Regardless of taper, and all that mystical mojo, cases are made out of brass and will stretch. There may be bolt load reduction due to friction and stretching but it is inconsistent and not to be relied on in any way.

Apparently the standard 30-30 is strong enough not to lose its case head without the AI taper.

http://gunsmithtalk.wordpress.com/2008/08/19/ackley-bolt-thrust-tests/

I have not seen actual pressure test data verifying his claims of more velocity with less bolt thrust. If you notice, P.O. Ackley never conducted his test with a 30-06 or a similar high pressure cartridge. I am certain those would have blown right out the back of his lug less rifle. Ackley and others did not conduct sensitivity tests, varying chamber finish, (chrome for example), powders, primers, or much of anything else. I totally disagree with the implicit conclusion that Ackley and others have drawn, which is if Ackley improved cartridge reduces bolt thrust, a user can just pour the coal into the cartridge and let fly. Ole P.O. was interested in promoting his cartridges, found a “one off” and left a very misleading legacy in terms of case friction, load, and chamber roughness.

I have read both of Ackley's handbooks and I don't recall seeing any pressure data on his AI cartridges (please correct me if I'm wrong, as it's been 20+ years), so your blanket statement :"...these improved cartridges actually ran at higher pressures." is at best a guess. Cartridges, by design, don't run at higher pressures as though it's come uncontrollable factor. As we all know, higher than normal pressures are most always attributable to loading practices.

The primary goal of reducing case taper and increasing shoulder angle is simple; to increase case capacity thereby increasing velocity potential.

Evidently all his experimenting wasn't without merit as todays newer cartridges, oddly enough, resemble AI cartridges. The WMS line, 22 & 6mm PPC, etc. When's the last time one of the major ammunition manufacturers introduced a cartridge with steep body taper and a shallow, sloping shoulder? I wou;d say somewhere around 1925 when Holland & Holland introduce the 300 H&H.

35W

quartermaster
February 13, 2012, 09:19 AM
I don't feel that case stretching and failure is a problem after you get past the fireforming procedure. I would expect that most people would just neck size or set the shoulder back .001 or .002 elimimating excessive expansion from that point and on.

On the other hand, I'm not sure about pressure issues. Personally when I fireform my 25-06 cases into the AI chamber I have intentions of starting at a bit less than max loads for the parent chamber and doing whatever is necessary to fully form the case. I would expect with the second loading that pressure could be kept in check utilizing powder choice and charge accompanied with primer selection.

I also considered the 6.5-06 before making my selection. I just love the 25's. Good luck with whatever you decide on and let us know how it works out for you

This will be my first dealing with an AI cartridge. I'm looking forward to the experience and figure on taking my time and carefully working up to where I hope to get. Time will tell.

SlamFire1
February 16, 2012, 11:06 PM
I have read both of Ackley's handbooks and I don't recall seeing any pressure data on his AI cartridges (please correct me if I'm wrong, as it's been 20+ years), so your blanket statement :"...these improved cartridges actually ran at higher pressures." is at best a guess. . As we all know, higher than normal pressures are most always attributable to loading practices.


There is not any pressure data in PO's book. There is load data, and if you look at the load data for standard cartridges, the maximum are several grains over today's measured data.

I have not seen pressure data on the Ackley improved. I look at the increased velocities ole PO got and don't see how he did it without increased pressures.

Cartridges, by design, don't run at higher pressures as though it's come uncontrollable factor

Since PO did not use pressure gages in the development of his improved cartridges, then what did he use in "designing" his cartridge?

35 Whelen
February 16, 2012, 11:41 PM
.


There is not any pressure data in PO's book. There is load data, and if you look at the load data for standard cartridges, the maximum are several grains over today's measured data.

I have not seen pressure data on the Ackley improved. I look at the increased velocities ole PO got and don't see how he did it without increased pressures.



Since PO did not use pressure gages in the development of his improved cartridges, then what did he use in "designing" his cartridge?
Yes, they probably are over todays measured data. I have a few older loading manuals including a Hornady from the '70's. Their data likewise is well over todays data. I don't pretend to know why...different powder formulas? Fear of lawsuits? Who knows?

You stated:
Ackley was taking heat because he was getting high velocities from his improved cartridges, cartridges which were being used in actions not designed for the things. P.O. wanted to show that his speedy cartridges did not increase bolt thrust, and infact as a result of his experiments, claimed they actually reduced bolt thrust. Which was bogus as heck as these improved cartridges actually ran at higher pressures. Higher pressures increases bolt thrust, it does not lessen it. P.O got higher velocities through higher pressures.

First of all, please state your sources regarding Ackley "taking heat" because he was getting high velocities from his improved cartridges. Higher velocities were the primary goal of improved cartridges. You do understand the principle of improved cartridges, don't you? If not, let me explain:

The principle of improved cartridges is to take a given case and increase its internal capacity thus increasing its powder capacity which in turn increases the velocity potential over that of the standard case, NOT to have a new cartridge that runs at higher pressures. Think of the 257 roberts and the 25-06. Loaded with optimal powders for each cartridge, to identical pressures with identical bullets, the 25-06 will provide a higher velocity than the 257 Roberts...and so it is with the 257 Roberts and the 257 AI. If it weren't so, the improved cartridges would be worthless rather than alive and well 60-some years after their inception.
Bolt thrust blah, blah aside, if the improved cartridges ran at higher pressures, it was/is because they were LOADED to higher pressures...not because the improved case somehow magically created higher pressures. You state in the quote above "...these improved cartridges actually ran at higher pressures." then concede that Ackley's handbooks had no pressure data. So, how do you know they ran at higher pressures?

As one who's loaded the 257 AI since the '80's, I can tell you with 100% certainty that standard loads in the improved chamber actually created LOWER chamber pressure. I know this because I fire-formed quite a few 257 AI cases by simply firing a 257 Roberts factory load in the improved chamber. Measured MV's were substantially lower (hence indicating lower pressures) than advertised MV's.

35W

lefteyedom
February 17, 2012, 03:05 AM
Had affordable chronographs been available to the public in Mr Ackley (or Gibbs) day A.I cartridges would not have the following they do today.Now with chrony anyone can test the (wild?) claims of gun writers, reloading manuals and cartridge designers.

The basic designs of Mr Ackley cartridge are not bad.

Most A.I. do not delver enough performance improvement to justify the cost. What is the real value of 100 to 200 extra FPS if you are already making 2600-2800 FPS?

A range finder and a better scope would likely be a better use of one money.

All that said/// I would like to build a 6.5/06 AI...

35 Whelen
February 17, 2012, 07:43 AM
Had affordable chronographs been available to the public in Mr Ackley (or Gibbs) day A.I cartridges would not have the following they do today.Now with chrony anyone can test the (wild?) claims of gun writers, reloading manuals and cartridge designers.

Exactly. one of the things that made the 257AI so appealling was it was a vast improvement over the factory 257 Roberts loads because the factory loads were loaded to low pressures. Loaded to equal pressures, I doubt the 257AI has much more than a 100-150 fps improvement over the 257 Rob.

35W

helotaxi
February 17, 2012, 08:23 AM
Yes, they probably are over todays measured data. I have a few older loading manuals including a Hornady from the '70's. Their data likewise is well over todays data. I don't pretend to know why...different powder formulas? Fear of lawsuits? Who knows?
Better measuring technology. The old loads were developed using copper crusher test barrels that are not an accurate measure of dynamic pressure and pressure changes. With the advent and availability of modern strain gauges and piezoelectric pressure barrels with high speed capture measured in the microseconds, load developer quickly realized that the previously published loads were often grossly beyond accepted max pressure levels.

Coal Dragger
February 17, 2012, 03:30 PM
I have a .280AI chambered in a Cooper M52, and so far it has been an excellent combination. Accuracy is superb, and the claimed velocities in the Nosler Manual seem to be pretty accurate within 25-50fps, at any rate bullets hit where they should plugging the values into a ballistics program. I am very pleased with the rifle and cartridge combination, and have noticed no problems at all with feeding or any other issues.

quartermaster
February 17, 2012, 06:10 PM
"Accuracy is superb, and the claimed velocities in the Nosler Manual seem to be pretty accurate within 25-50fps, "

Sorry, I haven't figured out to do the quote box yet.

I always wondered about the velocity in the Nosler manual for the .280AI, as it always seemed to be quite a bit higher than other soures of data. I figured that they beefed up their velocities a bit to promote their rifle.

It's good to know that it's close. It may influence a future decision that I have been thinking about.

I will agree that there is not a great velocity increase in some of the AI's, but there are a select few which will gain a couple of hundred feet/second. But in considering the cost, you have to think about the fact that if you are going to go the route of a custom rifle, there really is no additional cost involved for an AI over a std cartridge. Granted you may have a bit more time involved with fire forming and may use a touch more powder loading, but even if the gain may be only 100 FPS, why not go for it? You also have the benefits which Kachok mentioned in the original post.

Coal Dragger
February 17, 2012, 07:20 PM
I can't speak for all the AI cartridges, but the .280AI is probably just falling into about the perfect case capacity for a .284/7mm bore. That magic area where you can still burn all the powder efficiently, but you are pretty much right at the limit of how much you can burn at the highest efficiency rate. Cartridges like the regular .280 Remington, and the 7mm-08 are still very efficient, but could actually use more powder for the bore diameter, and the 7mm Remington Magnum can burn more powder and get a little bit more velocity but the returns for burning the extra powder diminish and continue to the more powder you throw at the bore size.

So for 7mm/.284 diameter bores cartridges like the .280AI, 7mm Remington SAUM, and 7mm WSM are pretty much in that sweet spot.

As you noted in a custom rifle or semi-custom rifle there is not much you are compromising with an AI cartridge, other than the time involved in forming brass, and the higher cost of custom dies. In the case of the .280AI there is no sacrifice since factory brass is both excellent and available, and so is ammo. I think I read somewhere that Kimber is chambering rifles in .280AI now, so perhaps it will become a bit more common. It would be nice if another ammo maker would start offering loaded rounds and brass too, but for now Nosler components are nothing to scoff at.

If you enjoyed reading about "Thoughts on Ackley Improved cartrages" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!