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bullet/case neck run out

 
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  #1  
Old 09-24-2004, 11:07 PM
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bullet/case neck run out

Hi all,

I've recently got into neck turning with a couple of rifles, most notably a 300RUM. To completely clean up the necks, I've taken them down to about 14.5 thousandths. My neck wall thickness gauge shows all the neck thicknesses to be within .0005 when I finish up with a batch of brass (not sure how "acceptable" this number is, or not). I was curious how concentric my loaded ammo was so I put a batch of 29 rounds through the Sinclair concentricy gauge pretty carefully and got these numbers rounded to the nearest .25 thousandth that my strained eyes could determine on the dial gauge (I think I went cross-eyed a few times...) [img]images/icons/grin.gif[/img]
I don't think I can reliably give a measurement closer than .25 thousandths from a .001 dial gauge (not even sure about .25!). BTW, this is once fired brass and the 2nd loads were measured and I'm using the 180g Accubond. I also did not check the bullets by themselves for runout before I started this little experiment for which I'm kicking myself now. Bullet runout was measured about 1/16" in front of case and case neck was measured about 1/2 way up the neck.

Bullet runout Case neck runout

1. 1 1
2. 1.75 2
3. 1.5 1.75
4. 1 1.25
5. 1.75 1.75
6. .75 2
7. 2 2
8. 1.5 .75
9. 2.75 1
10. 1 1.5
11. 2 1
12. 2.5 1
13. 2.25 1
14. 2.25 1.5
15. 1.75 1
16. .5 .75
17. 1.25 2
18. 1.5 1.5
19. 1 .75
20. 1.25 1
21. .25 1
22. 1 1.75
23. 1 1.75
24. 2.5 1
25. 1.5 2
26. 2.25 2
27. 2.5 1.25
28. 2.25 1
29. 1.5 1.25

Questions:

1. When there are differences in these two measurements in a round, can it be wholly attributed to the runout of the bullet?

2. What are the "standards" for the various shooting disciplines in regards to these two measurements out of curiousity?

3. Are the kinds of number I'm seeing here typical numbers with some of the measurements of bullet runout and case neck runout the same in a round and others quite disparate?

4. Would I see more inherenent accuracy out of a round where the numbers are both, say, 1 and 1 vs. a round where the numbers are 2.75 and 1? What about 1 and 1 vs. 2.25 and 2.25? What's the relationship here?

Trying to get a handle on what these numbers mean.

Thanks for your help,

Jon Denham
[ 09-25-2004: Message edited by: Jon Denham ]
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  #2  
Old 09-24-2004, 11:11 PM
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Re: bullet/case neck run out

Sorry, I can't get the measurements to show up in a nice table format. It looks nice when I 'm posting the message but gets screwed up when I submit the post...
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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
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  #3  
Old 09-26-2004, 05:57 AM
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Join Date: Sep 2004
Location: CA
Posts: 2
Re: bullet/case neck run out

Answer to Question one – Not always, your reloading dies and press could have an influence on the numbers you are getting if either or both has a slight miss alignment. Starting out with high quality dies, like Redding, and a good press like, Forster’s Co-Ax or Corbin’s swaging press (either Dave’s or Richard’s) that can be used as a reloading press. Your firearm chamber might also be at fault, if it is not trued to the bolt and/or bore.

Answer to Question two – There is no standard per say, but there are acceptances. In hunting it is up to 4 or 5 thousandth out, in target shooting it is 2 or less, and benchrest shooting it is 1 or less, measured on the bullet’s shank about 1/16 to 1/8 in front of the case mouth. Less is always understood to be better.

Answer to Question three – I would say that your numbers are typical for hunting and unofficial target shooting but are unacceptable for official target and benchrest shooting.

Answer to Question four – I would say you would see better accuracy where the numbers are the same than different. If the numbers are different the better accuracy will come from the numbers that are the closest to each other. A 1 and 1 or a 2.25 and 2.25 indicate that the bullet run-out is zero and it is the run-out of the case that you are reading. You should see even better accuracy if you can get the run-out of the case to zero.

LadyHawk
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  #4  
Old 09-26-2004, 08:45 AM
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Re: bullet/case neck run out

I get the same. You'll probably notice no runout on the brass till you size(even just a partial NS). I isn't bullet runout, as that's probably less than you can measure.
The problem is in your sizing & seating system. And it's common.
All pieces in our system have tolerances which stack up in the abstract. Maybe a forster would help, I don't know. I've used a Harrell press, and Wilson hand dies/arbor. No effect, no change. Next would be to go away from bushings.
Good luck
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Old 09-26-2004, 09:42 AM
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Posts: 800
Re: bullet/case neck run out

Sometimes when turning necks after a firing or two may need to use an inside neck reamer get whats called the "dreaded donut". Mikecr is right your round is more concentric to the dies and press if using a standard set of dies and press. I follow more or less how the BR guys load. I try and make my rounds concentric to the chamber. I use either Wilson or Neil Jones arbor dies. If you go to a BR match and watch how those guys load don't see them worried about bullet run out. Now as to bullet run out. I think FiftyDriver has that down to an art and from his post I'd be asking him. To me he has develope a good style of reloading. Well good luck.
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Old 09-27-2004, 02:47 PM
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Re: bullet/case neck run out

Jon Denham, For my 300rum I use Neil Jones arbor type shoulder bumping dies and they run alittle over $200. after 3 firings I just need to set the shoulders back alittle or use a redding body die. After the first firing I use a inside neck reamer. With inline dies you don't size the body your main concern might be neck tension. Neil's bushing are made to match the shoulder and can be had with different neck sizes like wilson or redding and his seating die is also made with a bushing. On Neil's die if you had a 7,30 or 338 ulta mag you could use one die set for all those cal just by changing bushings and should work for the 30-378 and 338-378 wby. So somethimes the cost of his dies aren't that bad and he makes for threaded press also. I quit using FL dies over 20 yrs ago so any comment I would make is from that time so may not mean much today. Fiftydriver does alot of posting here and has address bullet run out a time or two so just look on some old post and will see his comments. Good luck.
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Old 09-27-2004, 11:09 PM
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Re: bullet/case neck run out

Hi and thanks for your replies Ladyhawk, Mikecr and Roper.

Ladyhawk: I'm using standard Redding dies in a 7/8-14 press. I the decapping/expander rod is floating via an 0-ring and my shellholder (Redding comp shellholder let me give a .002 shoulder setback)floats as well. Any other ideas to bring the system into better concentricity? This is factory rifle and I have lapped the bolt lugs using Brownells tool that does this aligning with the receiver thread, and I've also lapped the barrel/receiver joint for a good fit and bedded, adjust trigger, fully floated barrel, etc. Scope rings (Leupold Mark 4), lapped, etc. etc... However, as you mention, I'm not sure how good my chamber is as when I check runout after firing about 1/2 the case necks are right about at .001 and then other 1/2 are from .0015 to .002 or so. I thought that maybe I'm getting some "spring back" due to hard brass, etc. so I've been anealing every 2-3 firings and I still seem to get the same caseneck runout numbers after firing. Hmmm...not sure what to do next here. The rifle is shooting sub .5MOA most of the time and sometimes much better than that. But I get a flier ever 6-7 shots that I'd sure like to keep from happening.

It seems like that I have good cocentricity (less than .001 until I seat the bullet). Again, I've got the standard Redding bullet seater. What could be changed/done to improve the concentricity to this operation?

Mikecr: I'm not using bushing dies...yet. Perhaps this would help concentricity? Although your reply seemed to indicated going away from busing dies...to arbor presses? Can you size 300 UM brass with an arbor press?

Roper, could you link me to the post by FiftyDriver you're talking about? What do you mean by this exactly: "Mikecr is right your round is more concentric to the dies and press if using a standard set of dies and press."

Thanks all,

Jon Denham
__________________
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
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