Neck- vs. Full-Length Resizing

[Bart B.]

Where's that .002" difference?

Full length sizing dies for bottleneck cases have headspace. It's the distance from the die shoulder reference diameter to the bottom flat of the shell holder that's against the die bottom. The ones I've measured are universally about .005" less than the cartridge's rifle chamber headspace GO gauge. For example, 1.625" for 358/308/243 Winchester family cases.

They size fired cases' headspace back to about SAAMI minimum when the shell holder is against the die bottom per most die setup instructions. 308 cases end up with about 1.627" to 1.628" due to case brass spring back. That lets them chamber safely in SAAMI minimum spec chamber with 1.630" headspace with no more than about .003" head clearance.

 

[ireload2]

What do you mean where is it? It is a manufactured item and is subject variation on all dimensions if you measure enough of them.
You need to measure about 100 dies of all brands because they are not universally .005 shorter than the GO gage. RCBS dies are about half way between the go and no go. I have measured dies and still own some that are .031 short to .010 long.

I think you have not measured very many FL dies. You need to measure 5 or 6 of the same caliber and same brand.
Then measure the same caliber and different brand and you will have a better appreciation for process variations as well as variations between makers.

PS you need to review the .358 Win drawing because it uses a different datum diameter than the rest of the family so the head space numbers are different due to the different datum diameter. The datum is .420 diameter and the min headspace is 1.6205". Yeah I know it is the same geometry but Winchester used a different datum.

Where's that .002" difference?

Full length sizing dies for bottleneck cases have headspace. It's the distance from the die shoulder reference diameter to the bottom flat of the shell holder that's against the die bottom. The ones I've measured are universally about .005" less than the cartridge's rifle chamber headspace GO gauge. For example, 1.625" for 358/308/243 Winchester family cases.

They size fired cases' headspace back to about SAAMI minimum when the shell holder is against the die bottom per most die setup instructions. 308 cases end up with about 1.627" to 1.628" due to case brass spring back. That lets them chamber safely in SAAMI minimum spec chamber with 1.630" headspace with no more than about .003" head clearance.

 

[oldroper]

I have to acknowledge that I haven't been following recent thinking regarding resizing, but I get the impression, from this and other forums, that the current view is that full-length resizing may result in more accurate ammunition than neck sizing.

I've just returned to reloading after a few years in the rimfire world, and I had thought that by neck sizing, you were allowing the case to conform better to the rifle's chamber, keeping it better centered, with better accuracy the result. (This is assuming, of course, that the reloaded round will chamber without problems.) In the past, I have generally used Wilson chamber-type dies that leave some of the neck just ahead of the shoulder expanded, and the loaded rounds have been a nice fit to the chamber while still chambering with ease. My thinking has been that unless loading really hot rounds, this process should allow a number of reloadings before the need to FL resize and start over again.

So is this no longer the prevalent thinking in reloading circles? For context, I've just started reloading again with a Sako 6 PPC. Is there a better way to prepare my cases than my old practice?

Thanks in advance for your insights on this....

I have factory Sako 22ppc and varmint rifle 6ppc and it's rebarrel Sako 6ppc.

When that Sako 6ppc was factory I shot some pretty small groups using Wilson neck die mostly in the .3's. The Sako 22ppc I just neck size then bump shoulders back when needed.

If you still have dies and have FL sizer try see what happens and those Sako are pretty accurate at least mine was.

What brass are you using?

 

[Bart B.]

What do you mean where is it?

Dies have several inside diameters and lengths. Just wanted to know which one you referred to.

Both 308 and 358 chamber specs for breech to body-shoulder juncture and shoulder angle are the same. Head to body-shoulder juncture is dimensions "D" (.2000") plus "H" (1.2500") shown in SAAMI specs' for both cartridge's headspace gauges; both breech to body-shoulder juncture dimensions are 1.4500." It's shown in their table listing all shoulder breeching headspace gauge specs.

You need to measure about 100 dies of all brands because they are not universally .005 shorter than the GO gage

8 to 10 each of RCBS and Redding seemed good enough to me. Both die companies confirmed that's typical of their dies.

Do you shoot 100 shot test groups for each test load?

 

[Barlow]

At our cottage I have a 1984 hardbound issue of gun articles iirc are Field and Stream annual editions. An article by Dave Scovill in this book is about neck vs fls and how he was going to prove that neck sizing was the best way to get the most accuracy out of his Ruger 77, 7x57 Msr, as that was the way all benchrest and match shooters prepared their ammo. He went through a bunch of loads, and various test to find out the rifle was more accurate with full length sized cases. He was unable to understand (at that time) why this happened. Personally I full length size, but do not care how others do theirs. Barlow

 

[Bart B.]

he was going to prove that neck sizing was the best way to get the most accuracy out of his Ruger 77, 7x57 Msr, as that was the way all benchrest and match shooters prepared their ammo.

NRA high power match rifle shooters producing best scores on bullseye targets have full length sized their cases since the 1950's. But they're typically left out of such comparisons because most folks don't think their rifles and ammo is as accurate as benchrest stuff.

It's a well known fact that neck only sizing fired bottleneck cases can somewhat fix bad full length sizing tool setup and use.

 

[bsekf]

Which is it????

1. Full Length resize and don't worry if the expander ball upsets the neck or shoulder?

OR

2. Full length resize with a body die and then resize the neck with a collet or bushing die?

Bill "too soon old, too late smart"

 

[Bart B.]

Which is it????

You forgot number 3. Those 2 you mention are two-thirds of the most used ways.

3. Full length size in a standard die whose neck is honed out to some dimension smaller than loaded round's neck diameter.

Some are made with body dimensions only .001" smaller than that of fired case body and headspace dimensions. This is way straightest resized cases are made because everything's kept in perfect alignment in one operation.

Some use expanders to half way iron out neck wall thickness issues. But a few ten-thousandths difference or spread makes little difference because bullets push their mouths and throats out to their diameters.

 

[dmoran]

#4. Full length size with a F/L Bushing die

 

[T-shooter]

You forgot number 3. Those 2 you mention are two-thirds of the most used ways.

3. Full length size in a standard die whose neck is honed out to some dimension smaller than loaded round's neck diameter.

Some are made with body dimensions only .001" smaller than that of fired case body and headspace dimensions. This is way straightest resized cases are made because everything's kept in perfect alignment in one operation.

Some use expanders to half way iron out neck wall thickness issues. But a few ten-thousandths difference or spread makes little difference because bullets push their mouths and throats out to their diameters.

The expander ball in my Forster F/L does not pull the necks out of alignment and I have measured a few where the ball actually reduces the runout on the neck by a few 10/10,000's. In these and any other similar die, the shaft is able to move sideways and self-center in the neck while the top of the neck is still in the neck portion of the die being held in alignment. Just for fun, I'm going to resize and check a few cases with an old Lee F/L die.

 

[Bart B.]

5. Neck size and shoulder bump with a bushing die with a shoulder; Neil Jones makes these.

6. Crimp the mouth of a fired case with a standard seating die's crimping shoulder.

7. Squeeze fired case necks down with a larger caliber collet type bullet puller. 30 caliber necks with 33 caliber bullet puller, for example.

===========

This list is gonna grow......

 

[Bart B.]

the shaft is able to move sideways and self-center in the neck while the top of the neck is still in the neck portion of the die being held in alignment.

Yes, that happens. But uneven wall thickness at the shoulder-neck juncture sets up stress that springs back straight necks to a bit crooked. I did a bunch of sizing that way then used pin gauges in case necks to measure mouth-throat axis runout on cases at their sized diameter; not with a bullet in and expanding them. A few were a tiny bit straighter, vast majority were more crooked.

 

[T-shooter]

Yes, that happens. But uneven wall thickness at the shoulder-neck juncture sets up stress that springs back straight necks to a bit crooked. I did a bunch of sizing that way then used pin gauges in case necks to measure mouth-throat axis runout on cases at their sized diameter; not with a bullet in and expanding them. A few were a tiny bit straighter, vast majority were more crooked.

I just ran 3 cases that had less than .0005" runout in the center of the (turned) necks. I expanded them with a K&M expander, then ran through the Lee F/L die with the expander ball. It was set up as per the instructions and it moved the shoulder back another .005" and reduced the O.D. of the whole case. The runout went up to .0015" to .0020". Yes, the die and/or the expander in the die did pull the necks or shoulders out of alignment to some degree. I re-expanded and resized with my Forster die and it wouldn't correct them, possibly because the shoulder was .005" under what I have this one set up for. I tried to straighten them with a Lee Collet die and still had the same amount of runout. Is .0015" - .002" runout too much? It's more than what I want. I took the one with .0015" runout and loaded a 208g A-Max in it. Out halfway on the ogive it still only had .0015" runout. Still not too bad.

 

[Richard Coody]

What a pointless discussion. Both methods work when done correctly. Both have good points and bad. Whatever works for you.

Just my opinion. I have tried it all. I prefer full length resizing with a custom or simi-custom die. Hate donuts.

 

[ireload2]

All inside diameters and lengths have variations due to manufacturing processes. Even heat treat can cause varying expansion or contraction (shrinkage) of different lots of materials.

All of that about the .358 does not translate to the same head to datum dimensions though. The .358 uses a .420 gage diameter vs a .400 GD for the .308

8 to 10 is not a statistically significant sample size anywhere.
I have 2 RCBS 8X57 FL dies that have .004 thousandths difference in the neck ID.
I have 2 RCBS 40-60 Winchester trim dies that have a .020 difference in the neck diameter.
I once bought a set of RCBS .25-06 dies and the seater was crooked about .030. My rifle would not shoot better than 1.5" groups. RCBS replaced the entire die set and the rifle settled down to 5/8" groups. That was 1975....

You only have information from 2 die makers. Measure a set of Lyman dies and see what you think.
The last time I spoke to RCBS technicians they would do not release data about their die dimensions. They now consider it intellectual property.

The point I am making is that you cannot assume body diameters, head space lengths or neck diameter will be the same with any manufactured product. They do vary. You might want to check your dies to see if they are straight too.

Dies have several inside diameters and lengths. Just wanted to know which one you referred to.

Both 308 and 358 chamber specs for breech to body-shoulder juncture and shoulder angle are the same. Head to body-shoulder juncture is dimensions "D" (.2000") plus "H" (1.2500") shown in SAAMI specs' for both cartridge's headspace gauges; both breech to body-shoulder juncture dimensions are 1.4500." It's shown in their table listing all shoulder breeching headspace gauge specs.


8 to 10 each of RCBS and Redding seemed good enough to me. Both die companies confirmed that's typical of their dies.

Do you shoot 100 shot test groups for each test load?

 

[South Pender]

I have factory Sako 22ppc and varmint rifle 6ppc and it's rebarrel Sako 6ppc.

When that Sako 6ppc was factory I shot some pretty small groups using Wilson neck die mostly in the .3's. The Sako 22ppc I just neck size then bump shoulders back when needed.

If you still have dies and have FL sizer try see what happens and those Sako are pretty accurate at least mine was.

What brass are you using?

I'm using Norma 6 PPC brass. I gather most PPC shooters use Lapua 220 Russian brass and fire-form. I wanted to eliminate the fire-forming task, so bought 100 formed Norma cases.

I also have a .22 PPC (a Wichita Classic rifle), and Norma .22 PPC cases are available, so I'll use those for that rifle too.

Although off-topic, maybe this would be a good time to get opinions about Norma PPC brass.

 

[Bart B.]

The point I am making is that you cannot assume body diameters, head space lengths or neck diameter will be the same with any manufactured product. They do vary. You might want to check your dies to see if they are straight too.

I don't care if there's a few thousandths spread across their dimensions or a few MOA spread across the section axes. Most of my dies are marked with neck and body diameters at its front and pressure ring areas. There's a spread in them and they're so marked.

It doesn't matter to me if one lot of reloads has different point diameters a couple thousandths apart. They all center bullets to the bore quite consistently. Body and neck diameters play no part centering bullets to the bore center when my rounds are fired; except for that of the pressure ring about 2/10ths forward of the case head. .001" difference there means less than half that at the bullet tip. All bullet tips center in about half the spread of pressure ring diameters for rimless bottleneck cases.


What's the sizing die neck axis misalignment max error in AS's (SOA or MOA, if you prefer larger units) with shoulder and body axis that's allowed?

Nor are the barrels straight when bullets go through them. Different sections are bending different amounts and at different frequencies. Even the bore and groove diameters change sizes to look like a snake swallowing an egg while bullets go through the tight an loose spots caused by normal dimensional changes from shock waves promulgating back and forth in them.

 

[ireload2]

You are going to have to speak ASME Y14.5M Geometric Dimensioning and Tolerancing to me because that is the governing document for drawings in the US. SOA and MOA means nothing on the drawings.

I don't care if there's a few thousandths spread across their dimensions or a few MOA spread across the section axes. Most of my dies are marked with neck and body diameters at its front and pressure ring areas. There's a spread in them and they're so marked.

What's the sizing die neck axis misalignment max error in AS's (SOA or MOA, if you prefer larger units) with shoulder and body axis that's allowed?

Nor are the barrels straight when bullets go through them. Different sections are bending different amounts and at different frequencies. Even the bore and groove diameters change sizes to look like a snake swallowing an egg while bullets go through the tight an loose spots caused by normal dimensional changes from shock waves promulgating back and forth in them.

 

[Bart B.]

SOA and MOA means nothing on the drawings.

Seconds of arc and minutes of arc mean all sorts of things when one compares angle differences across axes of stuff.

 

[ireload2]

No that is totally out of place unless there is an angle specified.
If you want the closest thing to the straightness of the dies you have to look at the loaded cartridge drawing since the ammo is the product of the dies.
The cartridge has tolerance of plus nothing and minus .008 on the diameters.
Just talking about the case for instance
When the case is at its maximum diameters from one end to the other that is called maximum material condition (MMC).
The case has no tolerance for a banana shape at MMC. It is important to understand that MMC ammo has to have perfect form in order to chamber. If MMC diameter ammo is banana shaped it will not chamber because it exceeds the maximum envelope allowed by the drawing.
As the case deviates away from MMC the smallest possible cartridge is called least material condition (LMC). The LMC cartridge would be -.008" on ALL case diameters. You can consider the case as a banana shape that arcs from one side of the chamber at the head to the opposite side in the middle and back to the same side of the chamber at the neck. That means the case has an arc of .008" over its length. That would constitute acceptable ammo according to SAAMI and it will still chamber at LMC.
The banana shaped ammo would correspond to .228 degrees, or 13.7 minutes or 821 seconds if you do not understand the LMC terminology. However that is just a conversion using trigonometry. The banana shaped ammo is governed by linear tolerances on the drawing.

I have never seen a FL die drawing that I can remember. However I would expect the die to be manufactured using best manufacturing practice and they should be able to hold plus or minus .002 on diameters. Yes they could hold tighter tolerances but they would a lot more expensive. Good manufacturing practice should produce a FL die that has all diameters on axis within .001 except - Heat treat can warp the dies and I doubt that is ever checked after heat treat.

Seconds of arc and minutes of arc mean all sorts of things when one compares angle differences across axes of stuff.