One Ackley improved experience

[Clark]

Jan 2000 I buy Keunhausen's scatter brained book on Mausers.
Feb 2000 I buy a VZ24 surplus rifle from BIG5 for $70.
Mar 2002 I buy a Lothar Walther .257 light varmint barrel $145

I get .257 Roberts Ackley Improved reamer from Dave Manson.
I build an action wrench.
I build a barrel vise.
I make an action truing mandrel.
I make a lug truing cartridge.
I make an inner C ring lapping tool.
I do a trigger job on the military trigger to control take up, force, and overtravel. Pull is down to 1 pound.
The bolt is bent with an Acetylene torch and sledge hammer.
I buy a Wheeler Eng drill and tap fixture and drill and tap.
Weaver #45 and #46 steel mounts are glass bedded to the receiver.
The barrel is dialed in on both ends of the lathe to within .0001".
Threads and chamber are cut.
The chamber measures still concentric on the lathe to with in .0010".
Stock is sporterized and glass bedded to the barrelled action.
A 40X Leupold scope is installed.
Barrel is cleaned and burnished with moly bore cream.
Winchester Brass is fire formed with 10 gr pistol powder and back filled with Cream of Wheat.
Case mouths are chamfered inside and out.
Forster dies are used on a Rockchucker.
Bullets are 75 gr Vmax moly coated for me by Russ Hayden.
Powder is surplus bulk military pull down IMR4895 that act more like H322.
Bullets are seated long to jam into the lands.

Late 2002:
1) 48.3 gr. gives 3757 fps and the extractor groove grows .0005"

2) 47.2 gr. gives 3736 fps and no extractor groove growth

3) 45 gr. gives 3674, 3621, 3630, 3614, and 3630 fps


A) All 5 shot 100m groups over last 6 years with 75 and 72 gr bullets average .87".

Can consistently shoot less that .5" when there is no wind at all.


B) With Hornady 100 gr soft point blem bullets, and 8.5x25x50 Mark IV scope, groups are less than 1" with 42 gr surplus bulk IMR4895 3220 fps

[918v]

Excellent writeup!

One question:

In your expretience, does the AI design minimize case stretching?

[Clark]

I headspaced with a 257 Roberts case.
Big mistake.
That does not allow for .004" of case crush from the firing pin pushing the case into the sharp neck 40 degree corner.

If the case is formed in one step, the case will stretch and separate right behind the shoulder.

So I have to half form with Cream of wheat or cheap bullets, and then shoot it normally.

After that, there is no case stretch, but I never get case stretch with any cartridge, as I never push the shoulder back more than .001", and I only do that very seldomly.

What does it all mean?
I don't have good case stretch data.

Do you want to mess with Ackley Improved chambers?
Everyone should have one, and then another 220 normal chambers.

[2400]

I headspaced with a 257 Roberts case.
Big mistake.
That does not allow for .004" of case crush from the firing pin pushing the case into the sharp neck 40 degree corner.

If the case is formed in one step, the case will stretch and separate right behind the shoulder.

So I have to half form with Cream of wheat or cheap bullets, and then shoot it normally.

After that, there is no case stretch, but I never get case stretch with any cartridge, as I never push the shoulder back more than .001", and I only do that very seldomly.

What does it all mean?
I don't have good case stretch data.

Do you want to mess with Ackley Improved chambers?
Everyone should have one, and then another 220 normal chambers.


I had a 257 AI, it was a great Deer, Antelope, long range windy day Coyote/Prairie Dog/Varmint cartridge.

I never had any problems with either case stretching or separations. I could form the AI just shooting 257 Roberts ammo. Which AI version do you have?

[Tailgunner]

Clark
I'm only playing with one "Improved" cartridge, and it's not much of a improvment (but the name itself is "cool").
Parent case on the left, fireformed "improved" case on the right. Of course when your starting with a 115gr water parent case capacity, how much improvment do you want in a 30cal?
http://i81.photobucket.com/albums/j212/Tailgunner1954/Picture215.jpg

[Clark]

I have the 40 degree original, not the RCBS moderate form.

[Tailgunner]

Clark
Your dealing with a "Mainstream" AI. A bud has one of the same thing, he's pushing 25-06 velocities out of it.
The one I'm playing with is a Ray Romain (sp) design, the parent case is the 300 RUM, the "improved" version I have is called the 300 Tomahawk (300 RUM Improved, 35^).

[Clark]

Sept 9 2003
A) 257 Roberts Ackley Improved VZ24, Lother Walthar barrel

I did manage to try the 75 gr. Vmax .257 bullets that I had coated.

1) 49.4 gr. of IMR4895 at 3.4" with Sinclair bullet comparitor gives
3942 fps and the extractor cut grows .0035"

2) 48.3 gr. gives 3757 fps and the extractor groove grows .0005"

3) 47.2 gr. gives 3736 fps and no extractor groove growth

4) 45 gr. gives 3674, 3621, 3630, 3614, and 3630 fps and a .9" group at
100m

5) 45 gr. with OAL 3.5" w/ Sinclair nut gives3674, 3621, 3630, 3614,
3630 fps and a .5" group at 100m.

What does it all mean?
It would do 4000 fps, if I want to sacrifice the brass

[45shortcolt]

Bolt guns will need to have the feedramp modified to allow Ackley cartridges (40 degree shoulder) to work from the magazine. If not you've got a single shot. Once so modified it won't allow regular rounds to feed properly. Something to keep in mind.

[MONTEGOD7SS]

The only Ackely I have experience with was a .35 Whelen Ackley and it fed standard .35 Whelen easy as ya please. Maybe some are pickey, but this one sure wasn't.