Long Range Hunting Online Magazine


Go Back   Long Range Hunting Online Magazine > Rifles, Reloading, Optics, Equipment > Reloading

Reloading Techniques For Reloading


Reply

Concentricity:How much ?

 
LinkBack Thread Tools Display Modes
  #29  
Old 02-12-2010, 11:50 PM
Bronze Member
 
Join Date: Dec 2009
Location: middle tn
Posts: 72
Re: Concentricity:How much ?

(www.6mmbr.com/TacticalFroggyA1.html)

Check out this link. He clears up a few things that can help get through the run out problem.

An area that's easy to ignore is the shoulder area and the importance in assuring it runs true.

The correct method of measuring depends on exactly what your trying to determine. (and I'm not sure what the NECO tool looks like) but:

The tool you are using is not an incorrect method of determining if the body diameter and neck outside diameter and bullet diameter are coaxial and that is the issue in part.

The tool you are using is probably the most correct of those I have seen on the market. I use a V-Block and indicator ( the indicator I use is not a drop indicator and allows me to access the neck id. I'll post a picture tomorrow.

It is not the method that can tell you if the neck diameters (i.d. and o.d.) are coaxial. (mine is yours isn't)

A drop indicator is really limited to outside measurement of o.d.'s (there are attachments to get to an inside diameter) but the wall or ball micrometer for wall thickness is our tool of choice. If the neck walls are not uniform the diameters are not coaxial. If the walls are not coaxial the bullet will not leave the case in line with the bore.

I have omitted mention of the shoulder diameter BUT if you can adjust your indicator so as to put the stem perpendicular to the shoulder then you could also check the shoulder coaxiality.

If it runs out chances are you will never have good bullet run out or runout tht you are looking for, like .001 or less . Read the link on 6br he talks directly to that relevance.

If the center line through the shoulder (cone) is not in line with the neck i.d the bullet will run out. SEE LINK he has nailed it.
__________________
don't ever be fooled into believing security is a good alternative for freedom.

Last edited by TnTom; 02-12-2010 at 11:58 PM.
Reply With Quote
  #30  
Old 02-13-2010, 12:07 AM
Platinum Member
 
Join Date: Nov 2003
Location: Washington State
Posts: 2,456
Re: Concentricity:How much ?

Concentricity Gauges - Hornady Lock-N-Load Concentricity Gauge Hornady's new design...

You guys think this would work as advertisted?

Noticed that the Forster Co-Ax design apparently doesn't accept cartridges with OAL longer than 3.5"
__________________
In the beginning God created the heavens and the earth. Genesis 1:1

"And can the liberties of a nation be thought secure when we have removed their only firm basis, a conviction in the minds of the people that these liberties are the gift of God?" Thomas Jefferson - Notes on the State of Virginia

www.wildsidesystems.com - Shelter for Your WildSide - http://www.youtube.com/watch?v=tYwgo...&feature=g-upl
Reply With Quote
  #31  
Old 02-13-2010, 12:17 AM
Gold Member
 
Join Date: Jan 2002
Location: Wenatchee, WA
Posts: 804
Re: Concentricity:How much ?

Quote:
Originally Posted by TnTom View Post
Bugholes from Bipod

Check this out. He clears up a few things that can help get through the runout problem.
Read it when it first came out; read it again just now. About the only major differences between his process and mine is I use a floating carbide expander ball, and my necks are squeaky clean (i.e. don't need to brush 'em) already. Since I have the same problem whether using a floating carbide ball in a Type 'S' F/L die or a Wilson neck die with *no* expander... that doesn't help much.

Quote:
An area that's easy to ignore is the shoulder area and the importance in assuring it runs true.
Any hints... ?

Quote:
The correct method depends on exactly what your trying to determine. (and I'm not sure what the NECO tool looks like) but:


NECO case gauge

Quote:
The tool you are using is not an incorrect method of determining if the body diameter and neck outside diameter and bullet diameter are coaxial and that is the issue in part.

The tool you are using is probably the most correct of those I have seen on the market. I use a V-Block and indicator ( the indicator I use is not a drop indicator and allows me to access the neck id. I'll post a picture tomorrow.
Which one? I mentioned three different tools...

Quote:
It is not the method that can tell you if the neck diameters (i.d. and o.d.) are coaxial. (mine is yours isn't)
If the necks have been turned with a quality tool such as K&M neck turner... how would the neck id and od *not* be coaxial? Are you talking about getting into inside neck *reaming*?

Quote:
A drop indicator is really limited to outside measurement of o.d.'s (there are attachments to get to an inside diameter) but the wall or ball micrometer for wall thickness is our tool of choice. If the neck walls are not uniform the diameters are not coaxial. If the walls are not coaxial the bullet will not leave the case in line with the bore.
I presume by 'drop indicator' you are referring to something like the Sinclair test setups with the dial indicator 'dropping' straight down over the case/bullet? Again, my case necks are turned, so shouldn't they be 'coaxial'?

Quote:
I have omitted mention of the shoulder diameter BUT if you can adjust your indicator so as to put the stem perpendicular to the shoulder then you could also check the shoulder coaxiality.
Probably doable with the NECO gauge.

Quote:
If it runs out chances are you will never have good bullet run out or runout tht you are looking for, like .001 or less . Read the link on 6br he talks directly to that relevance.

If the center line through the shoulder (cone) is not in line with the neck i.d the bullet will run out. SEE LINK he has nailed it.
We must be looking at different links... the one I read (specifically the second page on reloading) only gives the most cursory overview of what he does or why.
Reply With Quote
  #32  
Old 02-13-2010, 01:07 AM
Platinum Member
 
Join Date: Dec 2005
Posts: 2,114
Re: Concentricity:How much ?

Tactical Froggy's info on that 6mm BR link pretty much duplicates what I've been doing since the late '60's. I lapped out the necks of a few RCBS .308 Win. standard full length sizing dies to .332" and another thousandth for each successive die; I've got full length dies with neck diameters ranging from .332 to .337 inch now. Depending on the loaded round's neck diameter, I'll use a die whose neck is 2 thousandths smaller that it. I set the die in the press to set the fired case shoulder back no more than 2 thousandths. This prolongs case life and helps ensure the neck is well cenered on the shoulder. No expander ball's used. Cases are deprimed and cleaned before lubing and sizing. I use a 50-50 mix of STP engine treatment and Hoppe's No. 9 bore cleaner for lube. I dribble a bit in a foam lined coffee can on a Thumler's Tumbler and lube 20 to 30 cases at a time. This puts a very thin but consistant film of lube on the cases. Case headspace after full length sizing is most uniform using this lube and method; spread's about 1.5 thousandth. I probably would get better uniformity if I used Redding shell holders that come in 2 thousanths steps in height over .125 inch.

Full length sizing should reduce body diameters no more than a couple thousandths. That is good and normal for minimum SAAMI chambers which I use. So the shoulder-body junction is now a bit smaller than the chamber at that point. No interference happens like neck only sized cases have when the case has expanded enough that it's sllight out of round now interferes with the chamber when the case shoulder's prefectly centered in the chamber shoulder.

When a rimless bottleneck round's chambered, it bears against the chamber wall at its pressure ring 'cause the extractor pushes it there. Bolts with spring loaded ejectors in the bolt face push the round forward until its shoulder mates with the chamber shoulder; this part is centered in the chamber. It' even more centered when the firing pin smacks the case setting the shoulder back a few thousandths.

It doesn't matter how much clearance there is around the neck. My chamber necks are .344 to .345 inch and even with .334 inch diameter loaded round necks, they're well centered. If the neck ain't centered on the shoulder, even tight chamber necks won't help; the neck will still be off center in the chamber.

Putting the case through a nylon washer that bears mid point on the shoulder contacting it all the way around its circumference and resting the pressure ring between two ball bearings more or less sets up a datum line between center of the case mid point at the shoulder and center of the case at the pressure ring. The dial indicator is 1/10th inch back from the bullet tip to measure loaded round runout. A sized (or fired) case can be checked the same way with the dial indicator just behind the case mouth to check neck runout Both uses are based on the same datum or reference line.

As the shoulder's mid point circumference and pressure ring are the two contact points of the case against the chamber when it's fired, it seems right to me that they should be the basis for checking bullet runout.

Last edited by Bart B; 02-13-2010 at 01:17 AM.
Reply With Quote
  #33  
Old 02-13-2010, 01:41 AM
Bronze Member
 
Join Date: Dec 2009
Location: middle tn
Posts: 72
Re: Concentricity:How much ?

bart I agree, the datuming you describe if I understand you are including the shoulder and a point on the body diameter would create a C/L line most accurately thru the case that would be the most accurate method to establish datum C/L.

Milanuk,

I would modify the set up and try to use a dia near the rim but not on it and possibly a ring on the shoulder. It would take some fabing to include the shoulder as part of the alignment as bart is referencing then it would be an excellent tool.

If you you use two circle on the body to locate the case not including the rim it would still align accurately and you could indicate the shoulder.

If the neck is turned it would be concentric. No reaming. I was referring to indicating the neck id before a bullet is seated when I said getting inside, not reaming.

I was thinking you were using a something like the sinclair.

I don't think the Hornady that uses a point on the ogive and the rim is a great setup.

I've looked at so many in the last few days I need to go back and get them straight.

The neco I think has too large of a bearing surface ( the 2 V's) though moving the case off the rim might be an improvement.
__________________
don't ever be fooled into believing security is a good alternative for freedom.
Reply With Quote
  #34  
Old 02-13-2010, 08:54 AM
Gold Member
 
Join Date: Jan 2002
Location: Wenatchee, WA
Posts: 804
Re: Concentricity:How much ?

The NECO has several different possible configurations... the knife-edge vee-blocks are re-positionable, and there is a nose-cone for supporting the cartridge via the tip of the bullet, and a special chord for reaching inside a fired case to measure wall concentricity, etc. I don't have the manual for it handy, but I don't think the picture shown (stock picture off the vendor's website) is actually the configuration recommended in the instructions for doing loaded round TIR. I'll have to check when I get home this afternoon (headed to a 500yd F-Class match).
Reply With Quote
  #35  
Old 02-13-2010, 10:29 AM
Bronze Member
 
Join Date: Dec 2009
Location: middle tn
Posts: 72
Re: Concentricity:How much ?

i don't think any of the commercial R/O fixtures use the shoulder to set up the datum but they all should, do they?

I haven't but will make the bushings for my v-block to get on the shoulder correctly. I appreciate your pointing that out.
__________________
don't ever be fooled into believing security is a good alternative for freedom.

Last edited by TnTom; 02-13-2010 at 10:36 AM.
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes


Similar Threads for: Concentricity:How much ?
Thread Thread Starter Forum Replies Last Post
Concentricity? kc Reloading 9 04-05-2011 07:05 PM
Concentricity WV Sendero Reloading 13 02-16-2011 10:40 PM
Chamber concentricity toklat04 Gunsmithing 5 08-02-2008 11:01 AM
Chamber concentricity toklat04 Reloading 2 08-02-2008 08:15 AM
Concentricity StrayDog General Discussion 10 10-06-2004 09:27 AM

Current Poll
Do you archery hunt for elk?
YES - 29.76%
50 Votes
NO - 55.36%
93 Votes
Not yet, but I plan to. - 14.88%
25 Votes
Total Votes: 168
You may not vote on this poll.

All times are GMT -5. The time now is 08:48 AM.


Powered by vBulletin ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Management Powered by vBadvanced CMPS
All content ©2010-2014 Long Range Hunting, LLC