jmden
Well-Known Member
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...)
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 ]
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...)
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 ]