Concentricity/runout/neck dimension issue with 284 Winchester

[lawrence97]

I have a straight .284 with a .313 NK. I am using Lapua 6.5x284 brass and Berger 180 Hybrids.

Factory Lapua Brass: 2-3 thousandths of runout measured at neck.

Sizing/Expansion:
I am running a CoAx Press and a K&M expander Mandrel with a light coat of Imperial wax. I run the Lapua brass through the mandrel to bump it to 7mm. Everything feels smooth and not a lot of resistance in the process.

Measuring runout after the expansion yields the same results: 2-3 thousandths of runout.

Neck Turning:
I set my neck turning dimensions based on a .3125-.313 factory brass dimensions. After digging in several posts I found this: .313-.284-.003 = .026/2 = .013 Neck wall thickness.

I set up my K&M turner to shave the neck for a final thickness of .013.

After the neck shaving my runout becomes 5-7 thousandths !!!! While turning the brass feels smooth and the cut looks nice and straight....

Sizing with .309 Bushing:
After shaving and noticing the excessive runout I ran the brass through a Whidden bushing die and the runout remained unchanged.

Bullet Seating:
I then tried seating a 180 hybrid and the runout on the neck was 5-6 thousandths and the runout on the bullet was 6-7 thousandths. My loaded round is at .310.

Has anyone noticed this? Do I need to get one firing on the brass, resize, seat bullet and check again?

Issue is between expansion and neck shaving but not sure how to fix this. Any assistance would be appreciated.

Thanks

 

[fdshuster]

Re: Concentricity/runout issue with 284 Winchester

We just had a similar discussion, and the consensus was (and is), don't be concerned with runout until the new brass has been fired 1 or 2 times.

Check it then and you will see the vast majority will not have excess runout. There may be 1 or 2 that will, but those may have been defective from the time the cases were drawn. Identify those that do not straighten & use them for first round foulers, basic sight-in and close distances only.

 

[benjamin199]

Re: Concentricity/runout issue with 284 Winchester

Once the cases have been fired your run out should come back down.
.003 neck clearance is a little tight for the .284, I tried that with my first Fclass rifle and ran in to pressure signs at lower velocities than normal for the .284 Win.
I would recommend turning down your cases to at least .004, I am currently running .006 with good accuracy.

 

[DennisH]

Re: Concentricity/runout issue with 284 Winchester

.003 neck clearance is a little tight for the .284, I tried that with my first Fclass rifle and ran in to pressure signs at lower velocities than normal for the .284 Win.
I would recommend turning down your cases to at least .004, I am currently running .006 with good accuracy.

.004 minumium, accuracy is great between .004 & .006 on my 284

 

[lawrence97]

Re: Concentricity/runout issue with 284 Winchester

Got to fire 5 rds to check on fired case dimensions and the results are:
Chamber: .313 neck
Unfired-.310 loaded rd diameter
Fired-.3115-.312 neck diameter
Runout-now reduced to 1/2 - 1 thousandth

Questions..... What should I turn the remainder of my brass to given my fired dimensions? Or should I keep all my brass as is and turn after firing?

Those of you that are using .313 neck, what are your fired dimensions and what are you shaving your brass to?

I know some recommend .004-.005 clearance, but is that from .313 chamber dimension or based of fired brass dimensions?

Thanks to those in the know that are posting. Your knowledge is greatly appreciated.

 

[Erik Cortina]

Re: Concentricity/runout issue with 284 Winchester

From neck dimensions.

I turn my neck walls down to .012" for a .313" neck.

 

[TonyR]

Re: Concentricity/runout issue with 284 Winchester

I have found that the brass will straighten itself out on one firing if I anneal it after expanding and neck turning but before I fire it for the first time. Same thing if I've necked something down a similar amount. I know others think this a waste of time but annealing is easy with a machine and I have checked the runout with and without annealing enough times to believe in it.

 

[lawrence97]

Thanks for the replies. I will shave the brass down some more to get neck wall thickness of .012 and loaded diameter of .309.

 

[Steve Blair]

I run .004-.005" in my .284 Shehane in a .313" chamber. Try shooting your fire forming loads. Mine are very accurate.

 

[DennisH]

Someone asked for my chrono results using RL17. I will post them below

I used two chrono's because I didn't believe the below. They both were pretty close. My 284 loves 2,925fps

From Series 1 to 4 I know I was down to .2 grain increments. 52.5 was about the best it was gonna get. I tried this load 3 other times and the SD & ES both were below 5 on all groups. All ranged around 2,925 fps.

The others in regular print are there for reference. The Sd & ES were pretty decent on most of the groups.


Series 1 Shots: 4
Min 2883 Max 2898
Avg 2891 S-D 6
ES 15

Series Shot Speed
1 1 2891 ft/sec
1 2 2898 ft/sec
1 3 2895 ft/sec
1 4 2883 ft/sec
---- ---- ---- ----


Series 1 Shots: 4
Min 2920 Max 2922
Avg 2921 S-D 1 RL17 52.5
ES 2 BR2 CCI
180 Hybrids
Series Shot Speed Lapua
1 1 2922 ft/sec .050 off
1 2 2920 ft/sec
1 3 2922 ft/sec
1 4 2920 ft/sec
---- ---- ---- ----



Series 2 Shots: 4
Min 2917 Max 2941
Avg 2930 S-D 10
ES 24

Series Shot Speed
2 1 2934 ft/sec
2 2 2941 ft/sec
2 3 2929 ft/sec
2 4 2917 ft/sec
---- ---- ---- ----

Series 3 Shots: 4
Min 2942 Max 2962
Avg 2949 S-D 9
ES 20

Series Shot Speed
3 1 2942 ft/sec
3 2 2962 ft/sec
3 3 2951 ft/sec
3 4 2942 ft/sec
---- ---- ---- ----


Series 4 Shots: 4
Min 2956 Max 2967
Avg 2962 S-D 4
ES 11

Series Shot Speed
4 1 2967 ft/sec
4 2 2960 ft/sec
4 3 2956 ft/sec
4 4 2965 ft/sec
---- ---- ---- ----


Series 5 Shots: 3
Min 2782 Max 2794
Avg 2789 S-D 6
ES 12

Series Shot Speed
5 1 2794 ft/sec
5 2 2782 ft/sec
5 3 2793 ft/sec
---- ---- ---- ----



Series 6 Shots: 3
Min 2801 Max 2815
Avg 2805 S-D 8
ES 14

Series Shot Speed
6 1 2801 ft/sec
6 2 2815 ft/sec
6 3 2801 ft/sec
---- ---- ---- ----



Series 7 Shots: 4
Min 2818 Max 2832
Avg 2823 S-D 6
ES 14

Series Shot Speed
7 1 2821 ft/sec
7 2 2818 ft/sec
7 3 2823 ft/sec
7 4 2832 ft/sec

 

[Blaster-37]

Re: Concentricity/runout issue with 284 Winchester

I have found that the brass will straighten itself out on one firing if I anneal it after expanding and neck turning but before I fire it for the first time. Same thing if I've necked something down a similar amount. I know others think this a waste of time but annealing is easy with a machine and I have checked the runout with and without annealing enough times to believe in it.

I agree, one of the old school secrets.
Greg