Neck sizing with/without expander ball

[Win1892]

Getting some out of round necks with fired 338 Lapua brass, both new and after firing. Neck sizing is not restoring them to round. Don't want to pull an expander ball after the neck sizer as I want my neck sizer bushing to set neck internal dimension.
Question: use larger expander ball to restore concentricity to neck prior to neck sizing? Or run standard expander ball through neck after neck sizing, then neck size again without expander ball?

 

[243winxb]

If using a Redding S Fl die, use the expander when sizing. When using the correct bushing, you should feel very slight drag as the expander pulls thru the neck. Runout may be caused by sizing down .008" or more in one step. Use 2 bushings to size down in two steps.

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[GLOOB]

Don't want to pull an expander ball after the neck sizer as I want my neck sizer bushing to set neck internal dimension.

I'm curious. Why?

If anything, I would prefer an expander to set my neck dimension. Because it sizes from the inside of the case, and the inside of the case is where the bullet goes.

You can get a bushing just the right size for your cases, but only if your cases are matched or neck-turned, and only if the brass is of uniform thickness all the way around and along the case neck. With an expander, it's way easier to get uniform neck tension.

The major downside of using an expander is that to get consistent tension, you ought to size the case neck down a little more, leading to more work hardening. You can't do anything about that. Also, an expander can stretch a neck if it has been sized too small. The easy solution for that is to use a Lyman type rifle expander that expands from the top down.

 

[Bart B.]

It’s been a decades old myth that neck only sizing fired bottleneck cases makes them shoot most accurate. Sierra Bullets proved that back in the 1950's making the most accurate commercial bullets across all calibers and trying all sorts of resizing methods. They've used full length sizing dies since. It’s all because of what I call the “Dixie cup syndrome.”

Drop one of those cups in another after you've cut its bottom out. Notice how it perfectly centers inside the other one. Cut the top third off another (a little irregular shaped) then drop it in that same cup. Notice it also centers perfectly. If a drinking straw was somehow fixed on the center axis of the dropped in cup, that also will be perfectly centered in the middle of the other cup it was dropped into. Very large diameter straws or very small ones; they all end up perfectly centered in that cup that’s had so many others dropped into it. If that straw’s off center any amount, it’ll be equally off center in that cup its dropped into.

Rimless bottleneck cases are exactly the same when fired. They’re pushed full forward in the chamber by firing pin impact; their shoulder centers perfectly in the chamber shoulder. A .243 Win case centers its neck (and therefore, the bullet) perfectly in a .308 Win chamber. Doesn’t matter how much smaller the case body diameter at the shoulder is than the chamber is at that point. Just like that Dixie cup you cut the top third off of, the case shoulder centers in its matching chamber shoulder. Even with that shoulder-body juncture's a little bit egg shaped. It always is a tiny bit due to case wall thickness not being exactly the same all the way around.

The only way to make a size case neck well centered on the case shoulder when sizing it down is to have the sizing die keep the case body and shoulder perfectly aligned with the case neck. Neck only sizing die’s don’t do that. Full length sizing ones without floating bushings do. Dies with a floating bushing allow the case neck to be sized a bit off center on the case shoulder. Loaded round case necks are always smaller than chamber necks so there's no way that part of the case does anything to center it in the chamber when its fired; it's free floating with some clearance all the way around it.

Full length sizing dies with neck’s honed out to a bit smaller than a loaded round’s neck diameter make case necks much better centered on case shoulders. This has been the standard for benchrest folks producing the best results for a few years. They finally learned that while their smallest groups stayed the same size (there is a limit as to how small they can be), their largest ones were now reduced making group aggregates smaller. And as all cases and chambers are not perfectly round, it helps to have the case body a tiny bit smaller than the chamber body. Neck only sized cases soon start contacting the chamber body inconsistently which tends to off center their shoulders and neck in the chamber.

Full length bushing dies are better than any standard full length or neck only sizing die. Sierra uses Redding ones to resize their cases (those dies are made for) they shoot their bullets from for quality control. A standard full lengths sizing die with its neck honed out a bit is a little better. Forster will hone out one of their full length dies to a diameter spec’d by the customer; costs $12 nowadays. One of those Forster honed out dies is now the best bottleneck sizing die on the commercial market. Benchresters often have custom full length dies dimensions such to only size their fired case down about .001 in body diameter as well as set the case shoulder back .001"

If the case neck wall has a .001" spread, the hole in it where the bullet goes will be .0005" off center to the case shoulder axis; not significant. Even a .002" spread in neck wall thickness ends up with the bullet centered only.001"off center. That will never be a detriment to accuracy for any cartridge over 24 caliber; and then only if it shoots no worse than about 1/4 MOA at 100 yards.

Expander balls tend to bend case necks a little bit due to differences in drag around them in the neck as well as different case wall thicknesses at the case neck-shoulder juncture. It’s best not to use them but have the die’s neck sizing area about .002" smaller than that of a loaded round. That sizes the neck about perfect for all applications. If bullets are still not held securely by the case neck, then use the next larger bushing or open up the die’s neck another .001"

If you're measuring neck or bullet runout, best results happen when the tool's front reference is centered on the case shoulder. That eliminates any egg shape the case body has at its body-shoulder juncture. The back end of the case should have its pressure ring at the runout tool's rear refernce. That point on the case will be pushed off center in the chamber by the extractor; but only a thousandth or so. That'll change bullet or neck runout no more than half that amount. But its direction is always the same for every round fired so it's not a concern whatever it is off center at the chamber's back end.

 

[Patocazador]

I've used neck sizers to keep from excessively working the cases. Theoretically, it should extend the life of the cases ... No?

 

[Bart B.]

Yes, neck only sizing of bottleneck cases makes them last a long time.

But if you don't bump their shoulder back every once in a while, they'll grow enough in case headspace that they'll chamber hard. The bolt will bind a bit and need more force to close it on the chambered round.

That causes the bolt head to go into battery at some different place each time. And accuracy suffers. Benchrest folks typically full length sized their cases every 4 to 6 firings so their bolts closed without any extra force chambering them. As soon as the bolt started binding when chambering a round, accuracy got noticeably worse. Not by much, but 1/10th MOA was too much to put up with. All of which is why most of them started full length sizing their cases; minimally, but got overall better accuracy doing so.

Some of them get over 50 reloads per case. A recent record was set with cases full length sized (just a tiny bit) over 100 times. I got 47 times on a Federal .308 Win. case shooting maximum loads using a standard full length sizing die with its neck honed out to .002" smaller than a loaded round's neck diameter. All fired in a SAAMI spec chamber; then I ran out of test powder. A friend got 56 loads on one Winchester case full length sized in his die I honed out before he ran out of powder. All 56 shots went into 3/8th inch extreme spread fired from his rifle clamped in a machine rest aimed at his target 100 yards downrange.

 

[Walkalong]

Don't want to use an expander ball? Use a FL or neck size bushing style die, or get your sizer honed out to fit your case necks.

 

[taliv]

good info bart and walkalong

 

[Win1892]

Win243
My point is why use a specific neck sizer bushing to set neck tension if you drag the expander back through the neck changing the desired tension (inside diameter)
I use the redding s neck sizer die

I've played around with turning necks for consistent wall thickness and just want my bushing to handle the resize. That works fine until I get a neck that is out of round, because the neck sizer bushing does not always restore the neck back to perfectly round. Seating my bullet does, however, push the neck wall back to round. I'll look at concentricity on some of those finished rounds that had deformed necks and see if bullet seating was affected.

I know I'm splitting hairs here, but it's what I like about this hobby.

 

[Bart B.]

I understand your desire to have perfectly round case mouths after sizing them down from their fired shapes and dimensions. And you probably want best (or at least excellent) accuracy from your reloads, too. Right?

Here's some "hair splitting" stuff you might consider. . . .

First off, after you size the fired case neck down a bit, it's an "interference fit" between the bullet and case neck that sets some "release force" needed to push/pull the bullet out. It's the combination of the tension the case mouth puts on the bullet and the friction between them that determines that release force. The industry standard for all of this is called release force. Some military rifle ammo requires a 60 pound release force. Commercial stuff is less and some handloaders have it at only a few pounds for best accuracy. You can measure it by rigging a bullet puller off the edge of a bench then attach a shell holder to something you can fill with weight. Whatever amount of weight it takes to pull the case off that bullet is the bullet's release force.

Second, that release force doesn't vary much across a batch of bullets with some having zero spread in neck wall thickness holding them and others having a .0015" spread in wall thickness. I see no difference in accuracy with 30 caliber bullets in case neck with that much spread with release force spreads a couple pounds around 10. Sierra Bullets does no neck turning (nor any other case prep) on cases they full length size in Redding full length bushing dies used to test their match bullets in the 200 yard indoor range they have. Their 33 caliber heavy match bullets shot from 33 caliber magnum cases all have to shoot under 1/2 MOA to pass quality control. Their smaller caliber match bullets shoot in the 1/4 MOA range with those methods.

Therefore, I think you're trying to quarter those hairs instead of splitting them in half. If you want to shoot several dozen 10-shot groups to verify your detailed approach yields better results than what Sierra' already proved as good as it gets, have at it. I've always done what Sierra does in reloading. I tried a few tests with a couple cartridges with different release forces for bullets and neck wall uniformity; 'twas a waste of time and materials. Accuracy equalled what the best stuff of others did so I saw no need to split some of those hairs that so many people try.

 

[oldreloader]

The last 4 neck sizing dies I bought were the Lee collet neck sizers. They work great for me.

 

[gamestalker]

Uniform neck tension, and decreased neck tension is key to accuracy, thus I understand your reasoning here.

As for using neck dies, I got into a big neck die thing years ago, and to be honest the only real advantage I derived from neck sizing, was a slight increase in case life, but little if any improvement in accuracy. However, when properly done, FL sizing can arguably produce about the same case life as neck sizing.

I'm no expert here either, not by a long shot. But I recently decided to start turning my necks so I could gain some control over how much neck tension I get, and to obtain consistent neck tension. And the other nice pay off, is my necks are now consistently the same thickness all the way around.

So being curious just how much more consistent neck tension would be after turning, I performed a little neck tension test, something similar to what Bart B. described, except I used a trigger scale to measure "release force", and the results were really astonishing. Even when I did everything conventionally possible with multiple expander buttons, and doing it in stages from smallest to largest buttons, neck tension consistency still didn't come close to what I'm now achieving by turning them.

GS

 

[ku4hx]

I used a properly sized Lyman "M" die for all my bottleneck cases. Works good; lasts long time.

 

[fguffey]

http://www.lymanproducts.com/lyman/dies/pistolmdie.php

Then there is the alignment between the neck of the case and the bullet, I have a few competition seating dies by RCBS, the amount of force to seat is reduced if the reloader does their part.

There are many expander dies made and no longer used. The expanders are a good source for parts if the reloader has the a way to precision grind.

F. Guffey

 

[spitballer]

the neck sizer bushing does not always restore the neck back to perfectly round...

Roger that, especially when there's dings from being ejected. I've been using a small round rod to straighten the dings before sizing, but I'm also working on a small tool that looks like a miniature pipe wrench that will hook on the necks to straighten them.

 

[fguffey]

a miniature pipe wrench

I would suggest you use the rod in the neck to prevent the miniature looking pipe wrench from causing more problems that it cures.

Then there are holes, maybe a hole with a rod protruding from it.

F. Guffey

 

[spitballer]

True. Wouldn't make sense if I had to buy expanding equipment to avoid/repair damage.

 

[Bart B.]

When issued M118 match ammo, some lots had bullet runout up to .007". A 33 caliber collet in my bullet puller gently gripping a live round's neck eased the job of bending the neck by pushing on the case head. After writing the high point with a Sharpie with a number equalling thousandth of runout, 'twas easy and fast to straighten crooked ones to some amount .003" or less.

Typical accuracy improvement was 1/2 to 2/3 MOA. The worst lots of 7.62 M118 match ammo shot almost 3 MOA at 600 yards in spite of being spec'd at 3.5" mean radius at 600. That happens when there's some bad bullets held in crooked case mouths.

Cartridge spinners measuring bullet runout will give erroneous readings if the front reference is anywhere other than about mid point on the case shoulder. That's what centers the front of cases headspacing on their shoulder. I've yet to see a perfectly round case body close to its shoulder. The rear reference can be the pressure ring as that's presses against the chamber wall by the bolt's extractor. A .308 Win round that's perfectly straight will end up with the bullet tip about 0005" off center to the bore when chambered as the pressure ring's about .001" off center on the chamber.

 

[joneb]

I processed 100 F-C cases, I kept about 60% to reload. The problem with the other 40% was a varying case wall thickness at the mouth, which likely means there is a wall thickness variation through out the entire case.
I used a neck turning tool to identify the offenders to be culled.

 

[Bart B.]

You can also sort fired cases selecting those without the pressure ring being uneven around the case in front of the extractor groove. That pictured case has a full bulge opposite the side with no bulge. It has uneven wall thickness from head to mouth.

Cases with a measured neck wall spread of .0015" typically have a quite uniform pressure ring bulge. I've seen no accuracy/precision issues with that much spread on 30 caliber cases. A perfectly straight round with that spread will put the bullet .00075" off the bore center. Insignificant.

 

[GLOOB]

My point is why use a specific neck sizer bushing to set neck tension if you drag the expander back through the neck changing the desired tension (inside diameter)

Irony? Why try to set the neck tension with a bushing die, when it sizes the outside diameter. The bullet isn't gripped by the outside of the case.

 

[243winxb]

Seating my bullet does, however, push the neck wall back to round.

The bullet is acting as an expander.

 

[Bart B.]

To date, nobody has come up with a fired bottleneck case sizing die that:

* makes necks the straightest on sized cases with reasonably to perfectly uniform wall thickness.

* shoots all kinds of bullets most accurate.

* gives the longest case life.

. . . better than a gelded full length sizing die with its neck and body about .002" smaller than that of a loaded round; it springs back about .001" for decent grip on the bullet. The resized case body is about .001" smaller than a fired round's. Seating a bullet expands the neck about .001 inch.

Expander balls bend case necks on their way up and out 'cause shoulder walls are not uniform in thickness and nothing supports the rest of the case when that happens.

That's the current trend with the benchrest folks; took 'em near fifty years to learn that. Sierra Bullets proved that back in the '50's. Their smallest groups stayed the same size; the biggest ones got smaller.

 

[Win1892]

Bart

So you are saying FL resizing just enough to bump the shoulder back a couple of thousandths is the way to go, and possibly opening up the neck portion of the FL die a couple of thousandths to have a lighter grip on the projectile, as a neck sizer would do. I see where the bump back helps realign the "Dixie cup" cone shape, it makes sense.

Turn necks on new brass just to get better uniformity?

I agree with the concentricity gauge being placed mid shoulder as I am amazed at the "bent" cases I am seeing, even after multiple firings. I had anticipated fire forming would help straighten the bent cases but that is not happening. I load Norma cases for 338 Norma and the concentricity gauge goes nuts anywhere on the case body. My 6.5-284 is way better across the case.

Thanks everybody for putting the time into this thread. I'm enjoying it.

 

[Bart B.]

The main reason fired cases are bent is their wall thickness isn't too uniform all the way around. When fired, they stretch more on one side than the other. Right out of the chamber, they're bent. Full length sizing them doesn't straighten them very much.

The more head clearance (space between a loaded round's case head and bolt face when fired) the loaded round has in the chamber, the more a case body will stretch on that thin wall axis when fired. Minimizing head clearance by setting fired case shoulders back .002" max helps to minimize case body stretch. And squared up bolt faces makes case head contact with the bolt face more uniform all the way around; another help for best accuracy as it keeps case head's squared up.

Forster will hone one of their die's neck to whatever diameter customers want; costs $12 these days as I remember. They'll do that to a die ordered from them, too.

I've seen no difference in fired cases so sized with turned necks to zero spread in thickness to unturned ones with about .0015" spread. Done a few tests at long range with both case types but all shot the same 1/2 MOA or so accuracy with 15 to 20 shot test groups. One group was with new, unprepped 30 caliber magnum cases.

Remember there's no such thing as a perfectly round chamber or case body, but chambers are better than cases. And the back end of cases is not centered in the chamber when it fires; it's pressure ring is touching the chamber wall by the extractor pushing it there.