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Reloading Berger Bullets


case neck and bullet runout

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Unread 11-29-2013, 09:59 AM
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Join Date: Aug 2003
Location: NC, oceanfront
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Re: case neck and bullet runout

Originally Posted by dmax1800 View Post
1) why there can be more runout in the case neck than in the bullet; 2) which is the more important measurement, case neck or bullet runout for accuracy; and 3) if case neck runout is important, what can be done to correct it.
WOODS explained it well for a SAAMI (typical hunting) cartridge/chamber.

An unlucky friend had lugs badly lapped in a gun(unknown to him), and afterwards his go-to ammo started throwing shots all over the place. His ammo could show low runout(depending on gage), but the case heads were not square, as seen by rolling the cases across glass. After further work on the action and re-fireforming his ammo performed well again. I can only imagine his off-square case heads were setting a skew to cases chambered. And so I can imagine that crooked cases in general could cause throwing shots.
So I say the best we can do is make fully straight and square ammo, and use this in a precision fit chamber.
This is best seen with a v-block type gage, measuring TIR off necks AND bullet bearing.
But, with generous neck clearances and runout known to be neck thickness variance alone, a measure off bullets will suffice.
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Unread 11-29-2013, 01:47 PM
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Join Date: Jul 2009
Location: Sacramento, CA
Posts: 358
Re: case neck and bullet runout

Originally Posted by woods View Post
If you had thick and thin side on the brass of your neck that measured .015" and .013" respectively, you could have zero runout on the bullet and .002" runout on the case neck brass

But runout on the case neck is of little consequence compared to bullet runout

You could outside neck turn and solve the case runout but haven't accomplished much IMO
I was wondering about this. Thankyou for pointing it out. I had sorted all my brass be weight and neck runout and thought that the brass that was less than .002 would be perfect and the brass that was .005-.006 would be not so perfect.

Well after I loaded up my test loads I found out that was not the case. It seemed some brass just produced low bullet run out regardless of what the neck was, and then there was the brass that wanted to have more run out.

I will play with the expander die and mandrel when it shows up on Tuesday and see if it helps.
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