Site hosted by Angelfire.com: Build your free website today!

243 Ackley Improved Fitted

Case Neck Report.

29AUG98

The Goal of this evaluation is to determine if having a fitted neck, cases would improve the accuracy of my 243AI with its "standard" chamber. After fire forming several 243AI from 243Win cases I discovered 2 problems:

Since the chamber was already cut I was not able to specify a tighter and shorter neck than the "standard" 243AI. To overcome these problems I needed to start with a case that was both longer and had a thicker neck. The cases chosen were 30-06. After discussing this with Fred M. (a member of the 243AI group, 243AI-12a), Fred was kind enough to make me several 243 Win cases from 30-06 brass used for this evaluation. I hope to add the procedure to convert the 30-06 cases into 243Win AI cases in the future, for those interested in trying this. For now I will just say it is not a trivial task. Thank You Fred.

After receiving the cases and prior to initial fire forming, the cases were inside and outside chamfered. The flash holes were deburred and the primer pockets uniformed.

Max case length for my rifle measured 2.062" using a Sinclair OAL insert gauge.

The following table shows the measurements taken prior to reloading.

Case Number

1

2

3

4

5

Avg.

Case OAL

2.060

2.059

2.060

2.060

2.060

2.060

Neck Thickness

0.017

0.017

0.017

0.017

0.017

0.017

Neck Diameter (Before Seating Bullet)

0.2752

0.2757

0.2755

0.2752

0.2752

0.2754

Neck Runout

0.005

0.010

0.002

0.006

0.002

0.005

The cases were then reloaded as follows:

The following measurements where taken on the loaded rounds:

Case Number

1

2

3

4

5

Avg.

Neck Diameter (After Seating Bullet)

0.2763

0.2763

0.2763

0.2760

0.2761

0.2762

Bullet Runout

0.007

0.013

0.002

0.007

0.003

0.006

 

The following measurements were taken after the first firing:

Case Number

1

2

3

4

5

Avg.

Case OAL

2.050

2.050

2.050

2.049

2.045

2.049

Case OAL Length loss (From Initial)

0.010

0.009

0.010

0.011

0.015

0.011

Neck Diameter

0.2771

0.2770

0.2770

0.2770

0.2770

0.2770

The cases were then neck sized in a CH Necksizing die, and reloaded with the following components:

These five rounds were fired for group at 100 yards giving a group size of 1.087". For some reason this rifle is throwing the first round out of a cold barrel. Shots #2 5 grouped .255" at 100 yrds. This is consistent with a baseline group fired using 243Win cases, lot 243IMP0046. This lot has produced the best groups out of my rifle to date at 1.072". Again with shot #1 a flier and the remaining 4 going into .587".

The following measurements were taken after the second firing of the cases:

Case Number

1

2

3

4

5

Avg.

Case OAL

2.054

2.054

2.054

2.052

2.050

2.053

Case OAL Length loss (From Initial)

0.006

0.005

0.006

0.008

0.010

0.007

Case OAL Length Gain (From Forming)

0.004

0.004

0.004

0.003

0.005

0.004

Neck Diameter

0.2773

0.2773

0.2772

0.2771

0.2771

0.2770

The cases were then neck sized again with a CH Necksizing die and reloaded with the following components:

After firing the above loads the following measurements were taken:

Case Number

1

2

3

4

5

Avg.

Neck Diameter (After Seating Bullet)

0.276

.276

.276

.276

.276

.276

Bullet Runout

.003

.002

.006

0

.005

.0032

As you can see the run out is much better after the second firing of the cases. (The first full 243AI load through the cases).

The case length is still not what I want (.2057" is what I was aiming for) but is much closer then the 243Win cases. Some of the 243Win cases would get as short as ~2.025.

By using the 30-06 cases and fire forming using the "Cream of Wheat" method additional length can be gained, more on that some other time.

This has by no means been a conclusive test. I will continue testing as weather and my time available permits. It looks as though the longer and thicker necks of the cases add to the accuracy of this rifle. In addition the extra length of the neck makes for a more securely seated bullet and a better looking case.

So if you are like me and did not order your rifle with a tight neck, but would still like to obtain the extra accuracy that can come from a tight neck you have an option. The procedure for the thick and long necks can be found on the web page "Fred The Re-Loader". If you try this please let me know what your results are and we can compare notes.

Jeff in ND

milender@ictc.com