Fireforming to Ackley

[jackieschmidt]

Cases with quite a bit of body taper, such as the 22-250, 6.5x55, and the 338 Lapua, see a significant capacity increase when they are Ackley Improved.

Others, not as much. However, the 40 degree shoulder and minimum body taper is supposed to increase brass life and prevent excessive brass growth after repeated sizing.

 

[L.Sherm]

Theres not a case I haven't AI that I regret.
None have been difficult.
3- 280AI
6.5x06AI
20BRA
20PPCAI
20SCC

 

[SeabeeKen]

Have fun. I'm a varmint hunter. I always picked calibers based based on accuracy. I have a 6BR and a 6BRX. Both can shoot under .400" groups. I don't really get a kick out of owning rifles. I enjoy getting out in the fields where it's quiet and peaceful until I pull the trigger.

Ive got 243ai, 6mmai, 250ai, 257ai, 280ai, 7x57ai and all shot well under .5” and a couple shooting under .1”. My 6ai shoots .027” with 108 EH. I hunt varmints and deer with them. No complaints and kick is no worse than the parent cases. Brass has lasted over 20 years and counting.

 

[quartermaster]

Thank you guys. Your input has been helpful.

 

[DHD]

I have only a single 223AI. My cases shrunk about .010" with either WW or Lapua. After multiple firings, guess how much it has grown.

While I measure the case length after sizing, it appears none of my 223AI cases will ever need to be trimmed. I have read many times that the 40° shoulder slows down case length growth, and for me it appears to be true.

 

[quartermaster]

I have only a single 223AI. My cases shrunk about .010" with either WW or Lapua. After multiple firings, guess how much it has grown.

While I measure the case length after sizing, it appears none of my 223AI cases will ever need to be trimmed. I have read many times that the 40° shoulder slows down case length growth, and for me it appears to be true.

My experience also. I think bigger cases may shrink a bit more

 

[nmkid]

Zack built me a 243AI around 2021. I have yet to trim a single case back. Primer pockets are my problem. I like to run that baby at a rather warm pace. LOL.

 

[quartermaster]

Agree. The case may never need trimming, especially these days when the cases are short when they are new

 

[rardoin]

Don't pet the sweaty things. Seriously, though, just get a chamber length rod (non swiveling) with an oversized for bore bronze brush. When cleaning, run the bronze brush in the neck and twist/short stroke a few times. The ring will clear if one is present. I shot a 6.5x55 BJAI for a few years. Never had carbon that wasn't cleared by the above method.

 

[Fast14riot]

My 260AI brass shortens about .010" after 2 firings. I use a Lee case length gauge trimmer I shortened to match. Honestly I prefer cases being that much shorter in the chamber to give the carbon ring somewhere to grow that isn't in the freebore.

 

[RabbitSlayer]

It took 3 firings for all my 223 ai cases to grow to the book trim length. For those 3 firings I just chamfer. I then trim every firing like all my other guns to keep them all the same. I don't think there is any way around them getting shorter on the first firing.

I stay on top of the carbon ring.

Moral of the story, shoot more often so they grow faster!

 

[std7mag]

Do you know what the case length was before firing. SAMMI says 2.035 on an 7-08. Naturally new brass is always shorter in this day and age.
How do you like the AI. What velocity are you getting with the 140’s?
Curious how much case length you gain with each firing.

Sorry it took a few days to respond.

I didn't measure the virgin brass. I did run them through a full length sizing die then trim with the Lee case length gauge.

As for the 7mm-08AI, I like it.
The parent case doesn't have much taper to begin with, so the biggest gain in volume is from pushing the shoulder forward.
I gained about 1.5gr worth of powder capacity.
I gained about 50fps over standard 7mm-08 for the barrel length.
But it has the cool factor at band camp. Lol

My rifle is a Stevens 200. I reamed the factory 22" sporter barrel and set it up with the go gauge as my no-go gauge.
Lets the AI chamber fit tight to the shoulder/neck junction on a standard casing.
No need to jam the bullet into the rifling that way.

Using PPU (PVRI PARTIZAN) casings.
Fed 210M primers.
H414, IMR 4350, and Alliant PP2000MR gave me 2,832fps.
Yup, all 3 gave the same speed over 10 rounds.
RL17 was the speed demon at 2,916fps.

I didn't get the chance to test H4350, or Ramshot Big Game.

PP2000MR was my powder of choice. ES-6, SD-2 over 10 rounds.

I did try CFE223. Decent velocity. Accuracy eh. Couldn't get the ES/SD anywhere near acceptable numbers.
That and on hot days would blow primers.


I never measured after firing as my practice is to run them through the Lee case length gauge for standard 7mm-08 at each reload.
As I said, it doesn't take any off until 4-5 reloads. After that it will trim some off, just not a large amount.

 

[L.Sherm]

Years ago when my wife hunted I bought her a 7mm-08, after about a year loading for it I read an article about Hornandy light magnum ammo pushing a 139 at 3000fps because all I could get was 2850 with a IMR 4350 couldn't get anymore in the case so I bought a box of that Hornandy light magnum ammo sure enough over my chrono 2999 fps so I pull a round apart it was ball powder so I bought a pound of W760 then got 2975 with 140NP that shot well. It was in a 24" Rem factory barrel.

 

[Curmudgeon]

“Just wondering if someone could give me an idea of approximately how much shorter the neck would be? ”The OP asked about what length the neck should be. What does this mean? Is he expecting the neck to shorten?

 

[Oso]

Typical, Ackley Improved changes the shoulder angle to 40 degrees and also eliminates the taper in the case body. The net result is the cartridge body expands outward as taper is blown out and the shoulder is pushed forward to a steeper angle.

The case necks does shorten slightly as some of the material is relocated to help form the new shoulder.

 

[old_heli_logger]

Soooo, if your brass never gets long enough to trim, do you guys square them up and chamfer? Y'all do know that your case mouth IS your first crown, right? Start em out straight
Good luck

 

[std7mag]

Soooo, if your brass never gets long enough to trim, do you guys square them up and chamfer? Y'all do know that your case mouth IS your first crown, right? Start em out straight
Good luck

I've heard many times the "don't need to trim it".

But here in the real world, cases stretch from firing.
My experience with standard 7mm-08 and 7mm-08AI, along with 257 Roberts and Roberts AI is that it will take usually 4-5 reloads after fireforming to where you need to start watching the case length.

AI doesn't have to trim as much, but still needs trimmed.

 

[Oso]

Depending on the size of cartridge (diameter and amount of taper) as well as the rifle’s chamber, it will take several firing before the new AI case geometry stabilizes (2-4 firings). After each firing you can check by progress by measuring and tracking the case length and case base to shoulder to determine when the dimensions stabilize. During this period you are only sizing the case necks for first 3x firings. General guideline is that after the 3x firing you start FL Sizing the cases.

Depending on your shooting objectives, this is point at which you might elect to do an initial trimming to get a uniform case length for the batch of brass. Now that you’ve established a case length then business as usual going forward…trim cases as needed as they grow from future use/firings.