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Neck Concentricity Help

 
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  #1  
Old 08-11-2008, 06:52 PM
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Neck Concentricity Help

The run-out in the .257 Wby is back (or it never left this particular die).

The die is a RCBS Neck Sizing Die (not FL resizer)

If I leave the expander ball in the die, I get .004+" run-out. If I take the ball out, the run-out is .001" to .0015".

From what I can measure, a fired but not sized neck I.D. is .259/.260 from the Vanguard. With the sizing ball in, the I.D. measures .255. With the ball out, the I.D. measures .249.

This is NOT a bushing neck sizing die, so I cannot vary the amount of squeeze that is put on the case neck.

Is the I.D. of the neck too small for seating bullets without the ball expander in the die?

If so, what amount of interference fit should I be looking for between the neck and the bullet? I have a .25/06 Lee collet die that I changed to work for the Wby., but since I have two .257 Wby rifles, and I know that the chambers are different, I don't think I will get the best results using the same neck sizing die for both guns.

FWIW, the fired cases from the Mark V measure .255"/.2555" I.D., and the fired cases from the Vanguard won't allow the bolt to close when put in the Mark V chamber before resizing.

I don't mind buying a bushing neck die, but with a 30+ day wait, I'd really like to get this problem solved this week!

I tried lightly coating the neck with Imperial inside and outside, and also tried mica inside. All the cases are tumbled before they see the die (even the new ones).

Suggestions/tips/hints???
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  #2  
Old 08-11-2008, 08:05 PM
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Re: Neck Concentricity Help

Quote:
Originally Posted by esshup View Post
I have a .25/06 Lee collet die that I changed to work for the Wby., but since I have two .257 Wby rifles, and I know that the chambers are different, I don't think I will get the best results using the same neck sizing die for both guns.
How does the collet die know for which gun it is sizing the brass?

Actually, the collet die is sizing to fit the brass to a bullet, not a chamber. Use it for both guns and see what your results are.

Also, you can measure the run-out on the sizing stem for the RCBS neck-sizing die. It may benefit from straightening. Further, if you can leave the sizing stem/expander ball loose in the die, it will find its own center rather than deforming the brass.

You have several options.
.
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  #3  
Old 08-12-2008, 01:44 AM
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Re: Neck Concentricity Help

+1 on leaving the decaping stem loose so it can find center,also try polishing the expander ball a little.To polish the expander ball just chuck the decaping stem up in a drill and use some light emery cloth on it as you spin it. GOOD LUCK
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  #4  
Old 08-12-2008, 06:59 AM
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Re: Neck Concentricity Help

Thanks guys. I'll try both of the suggestions and report the results tonight.
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  #5  
Old 08-12-2008, 03:29 PM
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Re: Neck Concentricity Help

O.K., here's what I did, and the results:

Polished the expander ball, and left the stem loose in the threaded insert that threads into the die body. Lubed new brass that has .001 run-out and neck sized. .006" run-out. Tried tightening up the threaded insert, and left the lock nut loose. Sized another new piece of brass, same result. (well, .005")

Rotated the shell holder from the opening @ 8:00 to 4:30. Sized another new piece of brass with the stem lock nut loose. .002" run-out. Tried rotating the shell holder to different clock positions, and got between .004" to .006" run-out, with the exception of the opening @ 11:00. Then the run-out is back to .002.

I cleaned between all the mating pieces, and no change (it wasn't dirty, but you never know.....)

I tried loosening the lock-nut on the die body and letting that float in the press along with the expander ball stem float in the die body - .003" run-out.

These are total run-out numbers - the complete movement of the pointer on the concentricity gauge.

I give up! Suggestions??

Update:
AAAARRRGGG!!!!! I called RCBS and Brian there said: "If you're reloading, I don't think you can get better than .003" total run-out. You can send the press back so we can check the ram to die body alignment if you want." I didn't have the heart to say he was full of.....

I'm about to order a new shellholder and bushing neck sizer. What size bushings should I order?
Loaded round neck O.D. is .282"

I don't have time to send the stuff back, but I doubt that the press is the problem because when I load the .300 Win Mag I can get .001" TIR.......

Last edited by esshup; 08-12-2008 at 03:59 PM. Reason: Updated
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  #6  
Old 08-12-2008, 04:07 PM
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Re: Neck Concentricity Help

Is your shell holder floating?

Secondly, try loosening up the lock ring on your neck sizer and then lock it back down trying to not let it torque the die. If that doesn't work then turn the die about a quarter turn and lock the ring down again. Sometimes it is the act of locking the ring that will move it off. One one die I had to push on the die while tightening down the ring. Once I got it right I then locked that ring in real hard so I wouldn't have to do that again.
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Last edited by Buffalobob; 08-12-2008 at 08:51 PM. Reason: typo
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  #7  
Old 08-12-2008, 07:57 PM
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Re: Neck Concentricity Help

the best fix is to find a good friend that has a lathe. have him chuck up the die so it's spinning centered on the chamber, preferably on both ends of the chamber cavity, not the outside of the die body. now just take off enough metal from the neck to make it, i would say .254. now you don't need an expander ball and the necks will come out VERY straight.

also, when you size the brass, do it in several steps. just run it in the die a little at a time and spin it a third or half a turn between each sizing.
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