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Case Runout

 
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  #1  
Old 12-15-2002, 07:00 PM
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Location: Palmer, Alaska
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Case Runout

I got my Redding S sizer die for the 300 Ultra and was doing a little checking of cases on the runout guage with various cases in different states.

I was concerned with starting with zero runout of the cases before loading so I checked the cases that were just fireformed first. I found runout of between .002" and .005" on all ten cases I checked, hmmm...

Now I wanted to know if my chambers neck area was off center. I went back and used a magic marker and placed a line on the shoulder when the dial indicator was showing the extreme point of displacement of the neck. I then stood all cses up in a row with all the lines facing me. I looked at the cases carefully to see for evidence that the case necks were offset to the same side in relation to where they had beeen in the chamber. What I found was an angled scratch just below the shoulder that was on all cases in the same exact place in relation to the marks I put on all the cases. My chamber was indeed without a doubt off center.

Now that I know this is a fact, I tried to correct the runout with the bushing die. The runout remained in the same spot and by the same amount.

Now I checked the cases I had fired but then full length sized with my other die. All had less than .002" runout with most less than .001" and some zero.

The FL die was obviously straightening these cases out and the Bushing neck die was not. By this time I'm very disapointed but not really surprised by the different sizers affects on the already less than perfect cases, it made sense that the neck die would have less of a straightening effect in other words.

I do not want to FL size cases period, it is so much faster not to lube then neck size it isn't even funny. I did fifty cases in about 3 minutes on my Dillon so...

FL sizing will produce more concentric cartridges than the neck die will with fired cases out of this chamber but I'll find out how much difference on paper it makes shortly, IF I can EVER get to the range.

[ 12-15-2002: Message edited by: Brent ]
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Old 12-15-2002, 11:23 PM
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Re: Case Runout

Brent, I had a problem with both my .300 & .338 Ultra's and the Rem brass. I was getting 8 out of 20 rounds with bullet runout over .005". When I checked the necks after firing, the neck runout was zero for the .338, and .0015" for the .300, which told me that my chambers were concentric to the bore. When I checked the inside of the neck, I was getting .0025" or more runout. To make the O.D & I.D. of the necks concentric I neck turned the brass only enough to get 85% clean up, took less that .001" a side off to true them up. Most pieces had 100% clean up. I set up my full length sizing die to just bump the shoulder back .001" so the bolt will close without any resistance. Another thing I did find was that the expander ball was inducing some runout in the neck also, even though the die was perfect. I tried all the usual remedies to fix but didn't find a cure. I made up a seperate expander mandrel like the one Sinclair has to expand the necks for neck turning. I set it to give me .002" neck tension. Using this method I'm getting 2-3 "rejects" per 20 rounds now. I realize you don't want to use this process when mass producing ammo on a Dillon, but its helped my load accuracy for hunting ammo.
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Old 12-16-2002, 01:03 AM
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Re: Case Runout

Al,
I don't use the Dillon in the progressive sense that it is intended way anyway, I size all of them in the first position then do all my prep work and seat in the second station.

I have a carbide expander ball for the Redding dies and I use it to straighten out the screwed up necks on new brass and it works great, no lube needed and no necks to delube later. My 308 die doesn't leave too much tension without using the expander ball so it isn't used on it.

The check I did on the 300 Ultra FL sized brass used the expander ball because it squeezes the cases down too far unlike the 308win die I have. I haven't checked the Ultras runout without the expander used.

I was going to turn the necks, at least clean up 80% or better then I wouldn't need the expander anymore with the FL die, tension would then be about right with the thinner necks.

My pilot for the Forester turner is a tad too small and the case can literally be held up off the pilot and when the collet is tightened on the casehead and the case will stay off center of the pilot and cut the neck thinner on the side the neck it pushed tward when tightened, get the pilot too big and there a pain to work with too.

When I found the chambers neck to be off center I now wonder if the neck is centered with the bore or the case body is.

I had planned on leaving some of the neck unsized to help center the neck a little better with the loose factory specs and all, but now I wonder if I'm better off seating the bullets hard into the lands to center things up and leaving the necks sized all the way and loose to let the bullet center up, hell I don't know. I thought I might index the cases to the same position they were fireformed at and see how this worked too. I see a few tests down the road. Interesting little details can consume lots of time at the bench. I hope they shoot well with the neck sized cases reguardless of the runout, am I asking too much?
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Old 12-16-2002, 03:03 AM
 
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Re: Case Runout



[ 07-12-2003: Message edited by: S1 ]
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Old 12-16-2002, 08:04 AM
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Re: Case Runout

Brent, when I turn my necks I use the Sinclair tool . You have to use a special arbor to open up the necks so they are a tight slip fit on the turning arbor. Yea, it's a lot of work but you only have to do it once. I also tried to turn the necks to the point that when you ran them thru the sizing die, the die would compress them down to where the expander ball wouldn't open them back up. I didn't see any difference in accuracy between the two methods I tried. The only thing that bugged me was that gas was getting around the neck, the shoulder still sealed the chamber. Everything I've read seems to be that you want less than .002" total bullet runout for best accuracy out past 200 yards. I'm kinda picky with my loads. I can't blame the rifle when I miss, It's usualy the jerk behind the trigger. I guess it what your expectations for accuracy are to how much work you put into your loads. Mabey you could find a machinist who could make you a pilot for your trimmer. I haven't see a Foster, I make my own for my RCBS case trimmer.
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Old 12-17-2002, 12:52 AM
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Re: Case Runout

Forrester will make them whatever dia you need them but I just haven't got the one I need yet. I pollished the one I have down too much, so it's my fault it doesn't fit a tight now. I hadn't realized the collet would torque the case as much as it does. I could just pollish down an expander ball some to acomplish the same objective too.

I have my eye on a K&M turner for the future, I've heard nothing but the best about them so far.

I could have the chamber recut on the gun but it isn't worth the cash with the factory barrel in my opinion.
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Old 10-21-2003, 07:06 PM
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Re: Case Runout

i ran into a bullet runout faq the other day now i can't find it .anybody know where one is,thanks,keith
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