What have you guys found...

[Chappy]

To be the single biggest fix in fixing bullet to neck concentricity issues? I skim turn all of my brass and you a standard RCBS die with an undersized expander ball, then expand with a Sinclair expander die and mandrel. Has using an O-ring made a big difference for you guys? Just curious as I am happy with 0.003" of run-out for a hunting rifle but was just wondering if I can get it any better with the O-ring trick. Thanks!

 

[watercam]

I have been amazed at the minimal concentricity the O-ring trick has delivered with plain Jane sizing and seating dies. Works very well but do not crush the O-ring too much - perhaps 1/8 - 1/4 turn and mark the press and die to repeat the setting.

 

[jonbearman]

I know this is not what you want to hear however using the expander ball can sometimes be the culprit. Undersize or not. The oring idea is a good one and I would try it. Personally I have converted to almost all bushing dies and a Wilson seater and get very good results. It is a shame you couldn't get your rcbs die honed out to rid yourself of the spindle and expander. You could use a lee decapping die to pop them out and size with Honed to your spec die and either get a Wilson or a forster inline seater,they are reasonably priced. With my set up I get about a .001 or less in most cases.

 

[Chappy]

I know this is not what you want to hear however using the expander ball can sometimes be the culprit. Undersize or not. The oring idea is a good one and I would try it. Personally I have converted to almost all bushing dies and a Wilson seater and get very good results. It is a shame you couldn't get your rcbs die honed out to rid yourself of the spindle and expander. You could use a lee decapping die to pop them out and size with Honed to your spec die and either get a Wilson or a forster inline seater,they are reasonably priced. With my set up I get about a .001 or less in most cases.

These are just mainly for hunting rifles, not my competition rig. I can't see how two calibers undersized expander ball would affect the case mouth. But that's just me thinking out loud.

 

[Erik Cortina]

The expander mandrel is also bad news for runout. The reason is that the case is unsupported when the mandrel enters the neck.

You ask for the single best fix, here you go... custom dies.

 

[UltraBR30]

It depends at what point the runout is induced.
Is it from the chamber itself, or the sizing die, or when seating?
Figure out when, then find and fix the reason, is my advise.
Phil

 

[johara1]

I don't see a big difference, if you use a bushing die, and your free bore diameter is not overly big it will self alien. i sent some pretty crooked stuff down the pipe to see and it shoots in the hole. I don't buy all the BS. I do prefer under a .001 total run out but i found it is just a mind game. I see a larger dispersion with different neck tension than run out………. jim

 

[dkhunt14]

I agree with Jim. My buddy had a 308 Baer heavy gun and didn't like to neck turn. He would use 300 Weatherby which when loaded would run about 334 in his 336 necked gun. I used 340 Weatherby and necked down. When you neck down you gain .001 per side and have to turn. I said to him that why don't you let me turn a set for gun. I turned a set and shot his gun in a fun match. When I went to run the one case up in the die it caught, apparently I wasn't in the shellholder right. I loaded a bullet in the case and it looked worse then the leaning tower of Pizza. It was so crooked I set it in the block for sighter one. I skipped over it and started on sighter 2. I was centered and shooting in the patch and he said why didn't you shoot that one. I said I didn't want to chance messing up his gun. He said if it you can shut the bolt it won't hurt anything. He put the shell in and pounded the bolt shut. I fired and it went right in the patch at 1000 yards just like the 4 before it. Now I shot the 240 Sierras in the rifling and believed it bent the bullet straight. Matt

 

[ShootDots]

I don't see a big difference, if you use a bushing die, and your free bore diameter is not overly big it will self alien. i sent some pretty crooked stuff down the pipe to see and it shoots in the hole. I don't buy all the BS. I do prefer under a .001 total run out but i found it is just a mind game. I see a larger dispersion with different neck tension than run out………. jim

^^^^^ I agree with this. I have found I get more vertical with either the wrong or inconsistent neck tension..

 

[barefooter56]

Chappy,
An undersized expander ball used in a standard neck or full length die will result in more neck tension. Also the "o-ring trick" will work under the lock ring for the decapping assembly like it does for the die lock ring. Upgrading to a carbide expander ball if offered can also help. For full length dies set up the die so it only bumps the shoulder back .002-.003 . You will need a set of calipers, bump gauge body and appropriate inserts to find a the longest FIRED cartridge case you have. Or one that chambers a little stiff. Measure the case with the bump die (shoulder to cartridge case base) and note the length. Set up the die using a standard shell holder per the directions. Use the Redding competition shell holder set for your cartridge case and start with the .010 thick one and work down through the different thicknesses until you get the shoulder bump you want. There are other ways like adjusting the die in the press . But this is probably the easiest way. Not oversizing your brass can also help concentricity. We have found that 0 to .005 run out usually has no effect on accuracy. If you have any more questions please let us know.
Take care,
Phil Hoham
Berger Bullet Tech