THE MOST BASIC part of handloading for accuracy is resizing cases so they’re straight, all the way from the head to the mouth.  There are a bunch of solutions to the problem, but the simplest is forcing the case into a die that’s straight, all the way from the head to the mouth.

This is exactly how precision-made neck-sizing dies used by most benchrest shooters work, and also the way the cheapest dies of all work, the Lee Loader dies some of us started out with.  And believe me, Lee Loader neck-sizing dies will make ammunition as accurate as any — if the brass precisely fits the die.

That’s the problem.  Most of the brass we use isn’t as precisely made as our dies, especially in the neck.  The necks of standard factory brass often vary in thickness by several thousandth of an inch from one side to the other, or in overall thickness by a couple thousandths.  One of the most important “secrets” of handload accuracy is allowing each bullet to leave the case mouth the same way as every other bullet, and inconsistent neck thickness doesn’t allow this to happen.

This is precisely why benchrest shooters lathe-turn the necks of their cases to as exactly the same thickness as possible, and try to start with brass that’s as consistent as possible in the first place.  Unfortunately, most of us can’t afford to buy super-brass for all our shooting, and can’t afford the time to turn every neck.  Plus, it wouldn’t make all that much difference in most of our rifles.

However, we can sort brass, choosing cases with reasonably consistent neck thickness.  This helps to a certain extent, but then we still have to resize the cases so they’re straight all the way from the head to the mouth, and the standard sizing dies made by most companies tend to prevent this, because their “expander ball” tends to pull the neck out of alignment with the body of the case.

The expander ball is that lump of steel on the rod above the decapping pin.  Only rarely is it an actual ball; instead it usually resembles an elongated egg, or a cylinder with rounded ends.  We can easily prove it pulls case necks off-center by measuring cases in a concentricity gauge.

First, take a fired case and measure the neck’s “run-out” (the amount it wiggles the dial) on a concentricity gauge.  You’ll find there’s no more than .001 (1/1000^th) inch of deviation, and usually less.

Now, resize the same case.  As the case is pulled back out of the die, you’ll feel the neck being pulled over the expander ball.  Ninety-nine times out of 100, you’ll now find the resized case shows more run-out on the concentricity gauge, sometimes as much as several thousandths of an inch.

Finally, unscrew the decapper/expander rod and remove it from the die, then run the same case into the die.  You’ll find the case is now very straight again.

So if the expander ball pulls case necks off-center, why do most of the dies sold to handloaders use this system?  Because the necks of most cases aren’t consistent, either in overall thickness or side-to-side thickness.  To compensate, standard dies size case necks down more than necessary to hold a bullet, then the expander ball bumps the neck up to just under bullet diameter.  This is the cheapest, easiest way to deal with variations in case-neck thickness, and many handloaders are cheap, if not exactly easy.  (After all, the purpose of handloading is saving money.)

Why not just leave the decapper/expander ball out of the die body?  Unfortunately, pushing a bullet into this too-small neck often results in the bullet being seated crooked, exactly what we’re trying to prevent.  We can prove this by using the concentricity gauge again, but this time placing the spindle of the dial gauge on the bullet instead of the case neck.  (Ideally, we don’t want to size the inside of the case neck more than .002 inch under bullet diameter, and most standard dies size them down around .005.)

Now, due to the normal variations inherent in manufacturing, once in a while we can end up with a die that will size case necks down just right with the decapper/expander rod removed.  I have two in my collection of close to 100 dies, a .221 Fireball that does it with typical Remington brass, and a .300 H&H that does it with Winchester brass.  But this isn’t common.

With the right tools, we can hone out the neck section of a standard sizing die to “fit” the average neck thickness of the brass we’re using — but then that die is useless with other brass.  Which is, again, why standard rifle reloading dies have expander balls.

Now, we can buy other dies that size necks concentrically with the case body.  The cheapest are Lee Precision collet dies, which press the neck around a steel rod that’s just under bullet diameter.  These work very well — when they work.  I’ve owned a lot of Lee collet dies, but in recent years bought a few that simply couldn’t be adjusted to work right, a side-effect of producing “affordable” products.  (Don’t get me wrong.  I buy and use a lot of Lee stuff, but not all is precision-made.)

These days I usually use bushing dies.  These are pretty much the same as standard dies but with a removable neck-sizing section, called a bushing.  Instead of honing the neck section of the die to match the brass we’re using, we switch bushings.  I use Redding “S” dies, but bushing dies are made by other companies.  The only problem with bushing dies is the expense of buying more bushings, though normally measuring average case-neck thickness of a particular batch of brass will result in selecting the correct bushing.  In fact, I can’t remember a time when it didn’t.

Forster dies use another solution.  The reason the expander ball can pull the neck out of alignment is that, in most dies, the expander sits just above the decapping pin, low inside the die.  Consequently, the case is almost out of the die when its neck passes over the expander ball, and the case can tilt a little, resulting in a crooked neck.  (This is also why standard neck-sizing dies tend to produce crooked necks: There’s no support for the case body.)

Forster dies place the expander ball just below the neck cylinder of the die.  When the resized neck is pulled back over the expander ball, the case body is still supported, so can’t tilt, or at least not much.  The result is a straighter neck.

The trouble with Redding “S” and Forster dies is they’re more expensive to produce, so cost more than the standard reloading dies we can buy in almost any gun store for around $30.  About half the time standard dies produce fairly straight necks right out of the box, but if they don’t, a few tricks can solve the problem.

Sometimes the expander ball is slightly crooked.  This can be measured by placing the decapper/expander rod at an angle across a concentricity gauge.  If it’s crooked, you can then bend the rod so everything lines up.  (It also often helps to hone the expander ball.  I do this by sticking the end of the decapper/expander rod in a drill motor, then holding fine emery paper around the ball while it’s spinning.)

If that doesn’t solve the problem, expanding the case necks on the UP stroke of the press often does.  First, size all the cases with the decapper/expander rod removed from the die, then replace the rod and push the cases up over the expander ball.  The case is then supported squarely by the shellholder, and the necks tend to stay straighter.  The two disadvantages of this technique are that the case must be decapped by some other method (the reason I keep a Lee decapping die in one of the holes of my Redding T7 turret press), and the extra time involved — the reason I don’t use it for loading prairie dog ammo.  But it works fine for loading 20 or even 50 big game cartridges.

Another technique is to raise the expander ball higher inside the die body, like it is in Forster dies.  This also requires decapping by some other means, and doesn’t always work, especially with tapered cases that aren’t supported much by the walls of the die.  But with modern cases, with almost parallel walls, it works pretty well.

The only problem is that some dies don’t allow the expander ball to be raised as high as others.  Redding dies, for instance, typically only allow the expander to be raised about 2/3 to ¾ of the way up inside the die, while RCBS dies usually allow the ball to be raised until its right under the neck cylinder of the die.

Another technique, that can sometimes be combined with the others, is to loosen the decapper/expander rod slightly in its threads, allowing the expander ball to self-center in the neck.  This can be easily done with Redding and RCBS dies, but not with others such as Hornady and Lee that use a collet that tightens around the decapper/expander rod.  (This is one reason my shelves of loading dies are dominated by green cases, though there are some red cases as well.)

For cranking out LOTS of straight ammunition, I normally use more expensive dies designed for the job, partly because the accompanying seating die has a cylindrical section, slightly above bullet diameter, that helps keep the bullets straight as they’re being pressed into our straight case necks.  But for a lot of loading, especially big game cartridges, I use the standard dies we find on the shelves of sporting goods stores everywhere, because once we understand how they work, they can be made to do their job quite well.