does an improved case really improve

[dnb86]

So... only weirdos like "custom caliber" ?

Only the cool ones

 

[Koda_]

Cant say Id call an AI chamber a custom caliber...

 

[Mike D Texas]

A 260AI is a great example of improvement over a parent design.
The 260 is lethargic as under capacity for 140gr bullets. Ackley improvement takes you to perfect capacity for this.
You could go up to 6.5x284 or larger cases, but YOU WILL find lower efficiency and lower barrel life with this. Most people end up downloading the 6.5x284 to a point no better than a 260AI, while burning way more powder.

The way to see thjs stuff is to build a table, even if mental, of all cartridge design attributes (incl pros/cons) and rank them in comparison.
With this, it could be that there are situations where Ackley improvement is not a gain for you (or maybe anyone) (overall).
I imagine it would be easy for me to conclude that a 264wm AI makes an already extreme/bad design -even worse.
But for any caliber, I'm sure there is a better capacity cartridge for it that can be improved, leading to gains.

Don't be talking bad about my 264wm......it might not be a perfect design, but it's efficient for me as it is. With steep shoulders and almost no shoulder length it seems a waste on some improved designs. When a higher angle decreases shoulder length/space you lose capacity without lengthing the body. This is a reason the 260 out performs the 6.5creed even with lower pressure. Granted you'll need to throat it so the tail is in the shoulder that more in the body. This doesn't just apply to Ackley, but all so-called improved cases. Now take a fatter case increase decrease the angle and you have more capacity in the shoulder. Well you also have barrel burner like the wssm cases in 22cal. Maybe the 26 and larger cals would be a better suit for the wssm case?

Ouch Mike. That hits close to home. I love my 264WMI.
What do you feel is a bad design with the 264WM and exacerbated with the AI version?

 

[ARlife4me]

Ouch Mike. That hits close to home. I love my 264WMI.
What do you feel is a bad design with the 264WM and exacerbated with the AI version?

If you love it, then there's nothing wrong in your mind! There's only 1 way to improve the 264wm and that's by increasing the twist to 7.5 or 8. If 1 thinks you can't get enough case life out of it, then why am I getting more than 10X on the same brass. Good ole super-x from the 80's. I don't load light, I top out on pressure or real close to.

 

[Mike D Texas]

If you love it, then there's nothing wrong in your mind! There's only 1 way to improve the 264wm and that's by increasing the twist to 7.5 or 8. If 1 thinks you can't get enough case life out of it, then why am I getting more than 10X on the same brass. Good ole super-x from the 80's. I don't load light, I top out on pressure or real close to.

Oh I push this one hard, with throat burning powder too (N570). I've settled on a load that is just under 3350fps and shoots in the 2s consistently with 156 EOLs. The barrel is a 28" Proof 8 twist.
I do have a 26 Nosler reamer waiting for the throat to burn out on this one. I'll set it back and rechamber this barrel with it. Like the picture above the 26N will be properly throated for the 156 EOL as well.

 

[Plinker147]

Here is my take on this. I have one AI- 280AI for about 3 yrs now. It's my primary hunting gun and I really like the cartridge. I get 2850 with 175 Berger's and 3k with 162 EDLX 24 inch barrel good solid performance.

Reality is I haven't seen less case stretch, minimal velocity gains. I could probably push a standard 280 in 26in barrel close to the stats I'm getting. If I had to fire form case it wouldn't be worth it to me. I won't do another unless there is factory supported brass like the 280AI.

I believe the 30-35 degree shoulder are the sweet spot with performance, easy of loading, best all around. 40 degree have small but a few issues with donuts, easy of cycling and minimal performance gain for my uses. Most benefits from 40 are just from pushing pressures harder, the other slight benefits like suppose less Stretch, case life are too hard to measure for most of us. The more I've shot and played with different cartiridges the more I like the 30 degree cartridges.

 

[lancetkenyon]

Here is my take on this. I have one AI- 280AI for about 3 yrs now. It's my primary hunting gun and I really like the cartridge. I get 2850 with 175 Berger's and 3k with 162 EDLX 24 inch barrel good solid performance.

Reality is I haven't seen less case stretch, minimal velocity gains. I could probably push a standard 280 in 26in barrel close to the stats I'm getting. If I had to fire form case it wouldn't be worth it to me. I won't do another unless there is factory supported brass like the 280AI.

I believe the 30-35 degree shoulder are the sweet spot with performance, easy of loading, best all around. 40 degree have small but a few issues with donuts, easy of cycling and minimal performance gain for my uses. Most benefits from 40 are just from pushing pressures harder, the other slight benefits like suppose less Stretch, case life are too hard to measure for most of us. The more I've shot and played with different cartiridges the more I like the 30 degree cartridges.

Are you using Peterson brass?
I have found quite a bit less case capacity with Peterson than with Nosler, or other fire formed brass. So velocities will be lower like you are getting.
If you are not using RL23, try it. I get 2850 with a couple 22" .280AIs and 175 Elites using Peterson brass.
I got 2975 w. Nosler brass, RL23, and 175 Elites in my 26".

 

[Hugnot]

My favorite is the 6mm AI.

 

[VinceMule]

Ragged Edge, you are absolutely going to love a 260 AI~ Easy to tune with speed! This case is similar to a 6ppc in how easy it is to tune down to bug hole groups with various powders.

There are some issues in a Re chamber with alignment and bore dimension vs maybe oversize pilot size needed. A good gunsmith should fit the pilot dia. to the bore at the new throat

 

[Bob Wright]

Yes, an Ackley chamber has the higher velocity potential.
The attached screen shot is 280 Remington Federal ammo, 140 bonded bullet. Note the posted velocity.
My handload 280AI, solid copper bullet, not at max velocity, hits 3120 fps. There's more available, I just stopped here. That's on a 145 grain copper mono, mag primer, 58 grains of RE23.
Other members have pushed into 3200+ ranges with same components.
I think the Ackley chambers can open up velocities and reduce case maintenance as P.O. Ackley intended. Not all AI chambers "wow" in every instance. You would need to dig into it.

 

[VinceMule]

Due to pumps and semi auto's, the std 280 Rem is a down loaded specimen in factory ammo. Hand loads are quite a different matter, consult the Nosler manual #4. I shoot their accuracy load with IMR 7828, Fed 210, 160-162 of various types at 2900-2930 fps. Federal brass is soft in the case head...junk to me.

 

[Mikecr]

Ouch Mike. That hits close to home. I love my 264WMI.
What do you feel is a bad design with the 264WM and exacerbated with the AI version?

It's an extreme for the cal already.
Nothing is going to improve barrel or brass life, or efficiency for it.
Or put another way, by the time you did improve these things, it would no longer be anything like a 264wm.

I consider lasting accuracy (not fleeting) as the most powerful of ballistic attributes.
With this, the 260AI with a 140VLD can drop anything a 264wm can in my mind.
So that might sound crazy, but not to a another groundhog hunter.
If I'm presented with a larger game temple shot to 600yds, the percentages are far in my favor.

 

[Bob Wright]

Due to pumps and semi auto's, the std 280 Rem is a down loaded specimen in factory ammo. Hand loads are quite a different matter, consult the Nosler manual #4. I shoot their accuracy load with IMR 7828, Fed 210, 160-162 of various types at 2900-2930 fps. Federal brass is soft in the case head...junk to me.

Of course. That why hand loaded ammo can smoke factory ammo. Choose your components in an improved version and see where it goes.

 

[Plinker147]

Are you using Peterson brass?
I have found quite a bit less case capacity with Peterson than with Nosler, or other fire formed brass. So velocities will be lower like you are getting.
If you are not using RL23, try it. I get 2850 with a couple 22" .280AIs and 175 Elites using Peterson brass.
I got 2975 w. Nosler brass, RL23, and 175 Elites in my 26".

Nosler brass and R23