Factory neck dimension causes concentricity issues?

[Fritz Hagen]

Hi guys,

I have a question regarding runout (concentricity) problems that I have experienced in my factory 30-06 Tikka rifle. Currently shooting 185 Berger VLD at an accurate node velocity of 2740fps out of 22" barrel and performs surprisingly well out to 1100yds on steel. Will be testing on gemsbuck when the season starts. Precision is in the 0.6-0.8MOA range and ES at about 20fps. But one thing I simply cannot improve on is the runout measured on my case necks with a RCBS concentricity guage. I believe less runout will give me more consistent groups.

I have used Forster FL dies as well as the standard redding (non-bushing) dies but runout on the unturned Norma case necks was about 0.003-0.006" (and thats not even on the loaded round!). Not good enough for me !!! I have checked fired brass and there is absolutely no problem with my chamber itself, with runout of 0.0005"-0.001".

So in an attempt to at least halve the runout, I bought new lapua cases, turned the necks to 0.013", bought a redding type-s bushing neck die with a 0.332" bushing for a 0.002" neck tension. After firing these cases once, I was so excited to see what would happen after running these fireformed (straight) cases through the die. Unforntunately there was zero improvement. Runout was probably 0.003" at best. The die was set up perfect, touching the shell holder, 1/16" turn back on the decapping rod to allow self centering of the bushing, expander removed, imperial sizing wax used etc.

Now, I know I should have measued a fired case at the neck and added some for brass spring-back, and I'll do it later when I get home, but my theory is that the large factory neck dimension (probably 0.340" according to SAAMI) is causing my runout issues.

So I guess my question is this: Will reducing the neck from 0.340" to 0.332" cause runout? Should I rather do it in stages like 0.338 then 0.336, 0.334 and lastly 0.332? I really don't mind the effort.

I desperately need to get the most out of this rifle for at least another year or two until my custom build is finished, so any help will be appreciated.

By the way, great forum

Regards
Fritz

 

[Canadian Bushman]

I read an article by german salazar saying sizing down more than .005 ( diameter ) at a time can induce runout into otherwise straight brass.

Ive played with this and found that he was right and when i size down in steps my runout is significantly reduced and neck tension is more uniform as well.

 

[Fritz Hagen]

Thanks for the reply.

I think I will try doing it in steps and then report back if I happen to see any significant changes.

 

[Canadian Bushman]

Do that, itd be nice to know im not crazy and sizing down in steps actually makes a difference for others as well.

 

[kraky2]

You need to make small tweaks on the forester seating stem till the sizing ball gets centered.
If you can't find it try this...remove the expander ball from the forester.
Resize a case...I'll bet run out is near zero.
NOW...run that case up onto a expander on an "upstroke" on another 30 Cal die.
I'll bet you get almost zero run out again.....try it..its an extra step but will work very well.

 

[Gene]

The expander ball is most likely the culprit. Remove it and try again, or use the Redding bushing die, as Kraky says.
You might also want to try skim turning the necks.

 

[Fritz Hagen]

I'm already using turned necks and bushing neck dies without any expander.

 

[kraky2]

If you don't get good run out w/the redding try the steps in my post w/the full length traditional die. I promise it will work!

 

[Fritz Hagen]

If you don't get good run out w/the redding try the steps in my post w/the full length traditional die. I promise it will work!

OK. I'll give it a go Kraky

Thanks

 

[jsthntn247]

Your press could be the culprit.