Well,
I was just curious as to why I have seen many popular chamberings get an AI improvement done to them, yet have yet to find anything about such done to a 308? I take it that the gains made in doing so would not really make it worth while in ballistic performance due to the 30-06 and 300wsm? I just want to make sure that my thinking is on the right track for this one. Thanks.

Jerry

I know I will get flamed, but some cases respond really well. Some just look cool. Mostly all save on brass. You can burn more powder in an AI. All my rifles have an Improved chamber of some sort. Make them better some more than others. Plus none of my friends have them and guys get real curious at the range when i fireform. Everyone says, That can not be safe. How does it do that. Anyway. a 308 would not get anything from a AI chamber.

quote:

Anyway. a 308 would not get anything from a AI chamber.

And this is also true of all the .308 family of cartridges.

As a matter of fact it is true of almost all cartridges except those with a lot of body taper.

More baloney is connected to the AI cartridges than the 45-70!!!!!

Jerry, I own afew Ackley calibers and have been more than happy with them. I cann't say that I have ever considered building a 308AI.

I've shorten the 308 case and and use that wildcat with a 30 cal 1/16 or 1/18 twist barrel that case is kind of a mini 308AI it has 37degree shoulders. I forget who started doing the 308x1.5 then the BR guys also started shorten the 308 case for the 30x44,30x47,
30IHMSA etc.

If you look at the case capacity of the of the 284 case necked up to 30 caliber it just alittle over 4.00cc the 308AI is appr 3.85cc and since we are talking about maybe using a short action using the 284 case you save one step and that is fireform. So if I was looking at the 308AI be easier for me to do a 30-284 and I really don't think you would see much difference between the two. Just my .02

A couple of decades ago it was common for manufacturers to make 1 action length (30-06 lenth was called standard length) and to block of the magazine for short cartridges like 243, 308, 250-300 etc.

An easy matter to remove the block in the magazine and rechamber to 30-06 or 6 mm Rem and similar and that is what a lot of guys did. Another common one was 7x57 reamed out to .280 Rem.

So no real call for a .308 improved, but feel free to go ahead and do it if wish!

quote:

Originally posted by tom holland:
I forget who started doing the 308x1.5

Frank Barnes

roger

Just how much increased performance can you expect to get with improving the .308? I don't know the answer to that. I bet it aint much. So little it may not be worth the time and money involved.

quote:

And this is also true of all the .308 family of cartridges.

As a matter of fact it is true of almost all cartridges except those with a lot of body taper.

More baloney is connected to the AI cartridges than the 45-70!!!!!

I only have two rifles re-chambered to Ackley Improved cartridges. A .257 Roberts AI and a .30-06 with the Ackley shoulder moved ahead to the .30 Gibbs length. I have chronographed them both at 200-300 fps over their standard parent cartridges.

I have had them both for over 30 years, and each of them has taken scores of big game animals.

The baloney is in the freezer in little white packages!

AI shows the most improvement with cartridges with lots of body taper like the 22-250 AI. Short mags, 284 Win and 308 family would be a waste of time. 300 H&H AI, now that woud make a huge difference.

As you know! I live on wildcats and the AI is a good way to get longer brass life. Especially true in cases that are "sometime" difficult to get [250 Sav ie!]My 250 AI thinks it is a 25-06 with a short barrel doing 3100 fps with the 100s which is all I shoot anyway. As to the 308? I did it as an experiment back in the 70s and got 2 more grains of usable powder space and I believe it was 35 fps more velocity. I did, however, use the 35 deg improvement when I did a 308 necked to 338 for a guy in Hawaii many years ago. Main reason was better hreaspacing not speed. Ackley himself told me way back in the early 70s that, had he to do it again, he probably would have done a 35 deg shoulder instead of the 40. This would definitely have made for an easier job in the feeding end of life! I like the "Snob-Appeal" of the wildcats. Even if they don`t actually gain much over the standard cases they do set us apart from the guy who goes into X-Mart and buys his yearly box of Green/Yellow whatever the cal. As one of the other shooters mentioned-- it`s the little white packages in the freezer that tell the story. It is still fun to sit around a hunting camp and ,when asked what I am shooting, tell them I am shooting a 260 AAR or 263 Express. EVERY man to his own--mine are wildcats.

Aloha, Mark

I have a 280 AI and am building a .257 roberts AI. I personanly am not as impressed buy the 280 AI as so many seem to be.
While you certainly get a usfull velocity increase , in my opinion the main reason for the increase in velocity is du to the low preasure of the standard 280, not the AI case shape.
I am looking forward to seeing how much more powder I can cram in a .257 AI case compared to a standards Roberts.
I bet its some where beetween 3.5 and 5 grains.
Thats aproaching a 10% gain with some powders.
That does not mean of corse I will be able to use that much extra powder safly nor is it likly to give a 10% velocity increase.
But even a 5% velocity boost will be 100 to 150 FPS, worth while to me for sure !
But the 308 rounds are prety close to an ideal shape now.
I remember a guy awhile back who swore his .260 AI gave him a 300 FPS boost.
It might have of corse but he was way over preasure no queston.
...tj3006

Conversion rate from powder gain to velocity gain is about 4 to 1.. 721

quote:

Originally posted by vapodog:

quote:

Anyway. a 308 would not get anything from a AI chamber.

And this is also true of all the .308 family of cartridges.

As a matter of fact it is true of almost all cartridges except those with a lot of body taper.

More baloney is connected to the AI cartridges than the 45-70!!!!!

WoW Roger

When it comes to the AIs I can only share my actual experience with them as well as my own 280 base wildcats. Pretty much a Rocky Gibbs style with longer neck and 2grs more powder.

I've played with my case as well as many normal AIs over the last 25+ years. Many with strain guages checking the gains from the same barrel going from standard to AI to my own case.

For an 06 based case the 4 to 1 is pretty darn close if you add in equal pressures. For the 7x57 case it is a little better maybe 3 to 1 for the 308 it is worse on the order of 5 to 1.

What I found was that most of the claimed gains from the AI is do to pressure. The Roberts and 7x57 factory are loaded down. I would call 75% of the gain seen in them pressure and rest powder capacity. Key issue is finding a powder that will allow you to effectively use the extra capacity.

I built my wildcat from 243 to 416. While gains did happen they were not worth having custom dies made. Again just the opinion of a shooter with more Wildcats and AIs than factory.

Other key issue is many think the AI somehow makes the concern about pressure go away. What I found was pressure was still there. The AI might help hide it. You would see no sign until the primer let go. Doesn't mean that just below the primer going was a safe load (at least to me).

I've lost count of the amount of $$ I spent over the years playing with them.

If you want an AI then by all means build one. Hey main reason I started was to "be different". If you want 300mag velocities at egual pressure then shoot a 300mag.

Back when Speers #4 Reloading Manuals for Wildcat Cartrides was published (1959) was some intersting data about pressure with the 7x57AI here what was written, "P. O. Ackley, however,say he does not care what pressure are so long as he does not have extraction trouble or primer leaks, and he says that the straight body facilitaes extraction and prevents undue backthrust on the bolt. In that he is probably correct and more and more ballisticians are inlcined to agree with him. No pressure data for this cartridge is, of course, available, but experienced observers believe top pressures run around 60,000 psi or prehaps more". They also published data for a wildcat called 7mm/06 using a 160gr bullet velocity was around 2800/ 2900fps.


I shot a Rem factory 7mm Express before I had the 280AI build and who knows what the real velocity gain would of been had I been able to compare the 280AI against a custom 280 intead of a factory rifle. I did take rifles one was a 223 Hart barrel other 6Rem with a K&P barrel had both those rifles barrels set back and rechamber to the Ackley in 223AI/6RemAI and my velocity gain was over 10%.

I was surprised when I looked at IMR 2007 reloading data that listed loads for the 280AI and pressure around 61,000psi. If you look at the pressures from the Short mag Rem/Win it's around 60,000PSI, maybe those guys from around 1959 guessing pressure on a non belted mag case may of had something. Just my .02