bullet/case neck run out

[jmden]

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 ]

 

[jmden]

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...

 

[Donna]

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

 

[Mikecr]

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

 

[TOM H]

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.

 

[TOM H]

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.

 

[jmden]

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

 

[Mikecr]

Jon
What I was saying is that basically I have the same problem, and neither Wilson or redding neck sizing/bushing dies seemed to have any effect on it. That is, they did not fix it. So now I'm looking into body die configurations, in hopes of finding something that will not offset my necks when sizing. I'm begining to think I need something cut with a chamber reamer.

 

[jmden]

Roper and Mikecr, thanks for your replies.

I've thought some more about this problem and did some more reading and have done three things:

1) neck turn (I use Sinclairs 3000 turner and their special sizing mandrel beforehand.) a second time after firing. I was so careful the first time that I was amazed to see as much brass as came off the second turning. I did not adjust the cutter at all, in fact, when I saw how much brass was coming off I double checked to make sure the cutter was tight and hadn't moved.

2) Cleaned my dies extra carefully.

3) I chucked the expander rod in my drill press and at a slow speed used 800 then 1500 grit paper to polish it. Not too much, just a little. I did the same with the bullet seater, polishing the area when the seater contacts the bullet.

After FL sizing, all the cases (save one--which I'll probably end up pitching) had an average .001 runout some just a smidgen more some a smidgen less (using the Sinclair concentricity guage). (This is on a Rockchucker press with standard Redding dies with expander rod and shellholder floating and every bearing surface cleaned carefully. I clean and lube where the shellholder meets the ram so that it can float "easily".) After bullet seating the case neck runout varied just a bit more--anywhere from .00075 to .0015 with and average just a smidgen over .001. Bullet runout measured 1/16" in front of the case end was averaging just barely over .001 with a range of .00075 to .002. I think I can live with that. After all, this is just a hunting rig...

The expander opens the necks up to .304 (every single one exactly--outside is .335 exactly!) and my Accubonds measure just a hair under .308 so my necks are expanding .004 during the bullet seating operation. I'm wondering if there is anyone who can comment on this amount (.004) neck expansion (and associated neck tension)during the bullet seating operation?

Thanks,

Jon Denham

 

[brian b]

Jon Denham,
I have done exactly what you are doing,
if you are using a standard chamber you are
wasting your time neck turning infact you are
making matter's worse by making the neck
clearance greater. the best idea for a
standard chamber is to do a neck thickness
variance,use the correct size bushing to
minimally size your brass,then seat using
a redding,forster,wilson inline (BR) die to
keep from making matter's worse. I know that
neck turning is fun but it is counterproductive
in standard neck chamber's.
B

[ 09-28-2004: Message edited by: brian b ]

 

[Hunter66654]

Brian, I would like to be sure what you consider a standard chamber. In your definition would a chamber cut to minimum SAMMI specs in a new Kreiger barrel be a standard chamber or are you talking about chambers in factory barrels ?

 

[jmden]

brian b,

Thanks for your comments. It's truly interesting how many different opinions there can be in the the shooting world. In this case, some qualified folks say neck turning will help in a factory rifle, some equally qualified folks say don't bother. You mentioned the brass getting worked (moved) more after neck turning in a factory chamber, which would happen of course. My sized, neck turned cases mic .335 at the neck while untouched sized cases mic .3365. Fired cases expand to a whopping .345! However, do you think this .0015 extra expansion caused by neck turning just enough to completely clean up the necks is detrimental enough to offset the greater concentricity and more equal neck tension I'm getting with neck turning? I'm not sure if it make any difference but ogives are right on the lands (I'm able to magazine feed these with a Wyatt's box modified to truly center feed every case instead of just the last one...BTW, Jerry Teo, this modified Wyatt's box is working just fine although my magazine capacity has dropped from 3 to 2. However, I sure like the huge bite the bolt gets on the casehead with the center feed box. Much more confident in feeding now with the slightly rebated rim of the UM.). As long as the neck is sealing I should be alright? I'm annealing every few firings to help the necks...

Thanks,

Jon Denham

[ 09-29-2004: Message edited by: Jon Denham ]

 

[brian b]

Jon Denham,
You stated that your neck turned cases mic'd
.335 and after you shot them they were a
whopping .345
To put this into perspective say you go into
a department store to buy a new suit the
salesman measure's you and say's you are a
size 40 (your ammo) he say's the only size
he has is a size 44 (standard chamber) You
say I'll take it ,then to make it fit better
you go on a starvation diet (neck turning)
so you can be a size 39. It makes NO sense!!
Hunter66654 mentioned a minimun sammi spec.
that is the same as calling up a blind date
before you go to pick her up and she say's
I'M a small fat girl (oxymoron).
The point I am trying to make is what are
your goal's ,if you want the smallest runout
size your brass the minimum ammount possible
(the correct size bushing) but if your chamber is at least .010 larger than your
ammo it is a COMPLETE waste of time and
effort to neck turn,you might as well paint
your bullet's RED (because it look's fast).
the best thing to do for a standard chamber
is to get a redding S-die and get the right
bushing so you dont oversize your brass and
your runout will be acceptable.
If you really want to neck turn get a tight
neck chamber reamer so you are not wasting
your time.
roper mentioned that the B.R. guy's dont
check there runout that is true because
there chambers are only .002 at the biggest
over there ammo,if you only need to size .002
there is not much room to screw up,just touch
up the neck's and you are done.
If you need to size .010 you are really
putting pressure on the brass with standard
dies because they size them down (about .020
) then stretch them back out with the expander ball. (concentricity shot to %^&&.)
to put it in a nut shell if you have a
tight neck chamber turn the neck's to fit,
if you dont DONT
B

 

[TOM H]

Jon, If you turned your necks to .0145 thats is .029 add bullet dia and that is .337 less fired dia that leaves .008 so neck expands .004 each side now to see if it's worth the trouble I'd look for a black ring about 1/2 way down the neck and see if have thats even all the way around and if so that kind of know things are work. If not may want to turn necks to .015 or .0155 and see how they do or go more. You did alot of work on your existing dies but they didn't help you very much simple put your neck aligment is to the die and not the chamber if you make it to the chamber and your ojive are touching you get a pretty even jump with the bullets and lessen the chance of bullet distoration. If you marked the high side of that case used a set of inline dies loaded that round with the mark up your groups will be about the same without turning necks since your bullet distoration would be about the same(could do the same with regular diies). Br shooter mainly load from the neck up they know the body is concentric to the chamber as the neck so all they have to worry about is neck tension and seating depth. To me the trick is not the groups size but being able to shoot the same groups size every time. I don't want anyone to think my way is the only one some of us just get carried away. Good luck.