Full Length or Neck Only; What's Best Resizing for Accuracy?

Orange Dust

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Interesting, can you explain why the necks should be turned before they ever fired? Seems like if you sized fired cases with a mandrel type die that the imperfections would be transferred to the outside of the neck where the high spots could then be trimmed off?
Once the neck walls are uniform, fireforming will get everything straight. This is why I FL size after turning. It just makes the fireform load more accurate and useable.
 

Orange Dust

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Both Bart and JE are right as rain on all this. All three of us have a little different take on all the Why's, but are very close on the How's.
 

Bart B

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Bart B, To do what you are describing would require custom dies made from fired cases.
What post number are you referring to? Then I'll be able to better respond.

Is it #346? That doesn't require custom dies made from fired case dimensions.
 
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BountyHunter

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It requires dies that fit your chamber. It might be custom or might just be another mftr. The mtrs can order die dreamers anywhere in the saami specs. Jim Carstenson at JLC Precision can hone a Redding body die to your chamber and convert it to fl size bushings. My last one was $80 and about 3 weeks. I have seen a guy wear out 3 barrels in completion with the same 80 pieces of brass. Again for accuracy.
 

Bart B

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Sierra has used commercial full length sizing dies whose necks are a thousandth or two smaller than loaded round neck diameter. Honed out conventional dies or bushing dies. Best match bullets test 1/4 or better.

Forster hones out their full length sizing dies to customer specs for $12.

Smallest set of 10-shot groups at 600 yards I know of were made with cases full length resized in such dies. Rifle was a Hart barreled Winchester 70 shooting WCC58 cases and Lapua FMJRB 185 grain match bullets. Those ten groups measured .7 to 1.5 inches, then a 40-shot 1.92 inch group was fired.
 

Rich Coyle

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What post number are you referring to? Then I'll be able to better respond.

Is it #346? That doesn't require custom dies made from fired case dimensions.
That's the post. How do you know your die is going to size only .001" with out buying and trying it? If it is wrong then you buy another die.
 

Bart B

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That's the post. How do you know your die is going to size only .001" with out buying and trying it? If it is wrong then you buy another die.
It doesn't matter if the fired case body diameters are sized down .001 or .003 inches. The cases will be positioned very repeatable in the chamber from shot to shot when fired. Case body's pressure ring often touch the chamber when fired.
 
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tim_w

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[4QUOTE="Bart B, post: 1817554, member: 5302"]
It doesn't matter if the fired case body diameters are sized down .001 or .003 inches. The cases will be positioned very repeatable in the chamber from shot to shot when fired. Case bodies often touch the chamber when fired. [/QUOTE]

You are hopping around on the topic of effect it seems. The topic of relationship between die spec to chamber spec in terms of the amount of sizing was in response to your comment about 40+ reloadings FL sizing the case. It was not about accuracy potentail of how much a case is sized. There is no getting around that the more a case is worked past its yield/snap back the more it will work harden to the point of failure i.e. the more a case dimensions are expanded and then sized back down the shorter its duty life. Be it 20 vs 40 cycles or 5 vs 10.

I see zero beneficial reason in a hunting rifle for sizing cases more than is needed for reliable feeding/extraction. These are not combat focused guns i.e mil spec M4, M14, 1903 etc that need to work in those conditions and rd counts between basic maintance to include cleaning and the larger tolerances and config to allow for this.
 

Bart B

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tim_w,

Full length sizing of bottleneck cases headspacing on their shoulders has been the norm for best accuracy in all rifles, especially match ones, since the late 1950's. Case necks are centered best on case shoulders when the round fires. Cases do not lay in the chamber bottom when their primer fires.

This assumes the bolt face is squared up to the chamber axis. Otherwise, new cases, which are full length sized, will typically produce best accuracy. A good example is best quality M1 and M14 match rifles shooting commercial match bullets from new cases testing about half MOA at 600 yards. Reloading those full length sized fired cases with out of square case heads produced ammo that tested up to 1 MOA bigger.

Commercial rifles seldom have squared up bolt faces.

Accuracy is best determined by the size of the largest groups because they show how far bullets go from point of aim when all the variables add up in one direction. Smallest groups fired happen when all those variables cancel each other out.
 
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Mram10us

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I see zero beneficial reason in a hunting rifle for sizing cases more than is needed for reliable feeding/extraction. These are not combat focused guns i.e mil spec M4, M14, 1903 etc that need to work in those conditions and rd counts between basic maintance to include cleaning and the larger tolerances and config to allow for this.
Im a little slow, so what are you advocating?
 

J E Custom

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Interesting, can you explain why the necks should be turned before they ever fired? Seems like if you sized fired cases with a mandrel type die that the imperfections would be transferred to the outside of the neck where the high spots could then be trimmed off?

My reason for turning the necks before firing is because the thickness Of the necks are never exactly the same all the way around. So I use a sizing mandrel to make the turning mandrel fit the neck perfectly and then turn the necks to uniform thickness before the chamber offsets the neck bore by half the difference in the neck thickness.

If I turn them before they are fired, (New) they will be concentric with the bore after firing, instead of the outside of the neck being concentric the the neck chamber and not with the bore. After I use this procedure, everything will be concentric, the out side of the case and the inside of the neck.

J E CUSTOM
 

Tikkamike

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My reason for turning the necks before firing is because the thickness Of the necks are never exactly the same all the way around. So I use a sizing mandrel to make the turning mandrel fit the neck perfectly and then turn the necks to uniform thickness before the chamber offsets the neck bore by half the difference in the neck thickness.

If I turn them before they are fired, (New) they will be concentric with the bore after firing, instead of the outside of the neck being concentric the the neck chamber and not with the bore. After I use this procedure, everything will be concentric, the out side of the case and the inside of the neck.

J E CUSTOM
But wouldn’t it work just the same if you were to do it after firing then after turning necks everything would realign on the next firing? The reason I am asking is I’m considering starting to turn necks. Want to be sure if I do that I don’t have to start with new brass.
 

birdiemc

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But wouldn’t it work just the same if you were to do it after firing then after turning necks everything would realign on the next firing? The reason I am asking is I’m considering starting to turn necks. Want to be sure if I do that I don’t have to start with new brass.
Seems more efficient to do it before first firing that way everything comes into alignment then instead of waiting till after the second shot.
 

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