{"id":357,"date":"2017-09-02T12:02:02","date_gmt":"2017-09-02T16:02:02","guid":{"rendered":"http:\/\/www.floridareloading.com\/?p=357"},"modified":"2017-09-02T12:27:42","modified_gmt":"2017-09-02T16:27:42","slug":"neck-sizing-only-dies-how-to-use-them-and-when","status":"publish","type":"post","link":"https:\/\/www.floridareloading.com\/index.php\/2017\/09\/02\/neck-sizing-only-dies-how-to-use-them-and-when\/","title":{"rendered":"Neck Sizing Only Dies – How to use them and When"},"content":{"rendered":"

Rifle Cartridge Neck Sizing<\/h4>\n
\n

By design, when a bottle neck case is fired, it briefly expands to fill the entire chamber, then contracts slightly when the pressure generated by the burning powder dissipates, allowing the case to be extracted from the rifle. \u00a0 This is mostly due to the type of brass used for making rifle cases. The brass alloy is referred to as “70-30 Cartridge Brass”. It’s basically 70% copper and 30% zinc. It has the ability to work as described.<\/p>\n

If you wanted, you could take that freshly fired case and re-insert it into the bolt action rifle’s chamber. \u00a0 Not only would it fit, but it would be an exact fit to your rifle because it was fire formed in the shape of the chamber. \u00a0 If you wanted to reload this case to be fired again in the same rifle, all you really would have to do is clean it up, and reduce the diameter of the case neck enough for it to hold a bullet again – leaving the case shoulder and body in the as-fired condition. \u00a0 This process is called neck sizing only.<\/p>\n

When Neck Sizing Is Appropriate<\/b>
\nCartridges for a bolt action or single-shot rifles can be neck sized. \u00a0 Since the case has been fire-formed to a specific chamber, a neck sized cartridge can only be used in the rifle that last fired it. \u00a0 If your ammo is to be used in more than one rifle, you really have to full-length size it instead. \u00a0 Cartridges for semi-auto, and lever or slide-action rifles should not be neck sized because the cartridge-to-chamber fit is too tight for reliable feeding from the magazine, up the feed ramp, and into the chamber. \u00a0 Cartridges for these types of rifles (semi auto and full auto) should be full-length sized only.<\/p>\n

Neck Sizing Dies<\/b>
\nNeck sizing is best accomplished with a neck sizing die.\u00a0 This die is similar to a standard full-length sizing die except that the only part of the die that contacts the brass is the portion that resizes the neck. \u00a0 The part of the die that would normally size the body and shoulder of the case is oversized so that it will not form those parts of the case.<\/p>\n

Like a full-length die, the neck sizing die has a combination expander ball\/decapping pin. \u00a0 The expander ball in a neck sizing die performs the same function as the one in a full-length sizing die: The body of the die intentionally undersizes the neck, while expander ball enlarges it from the inside as it’s pulled out of the case.\u00a0 This allows the die to provide a consistent inside neck diameter regardless of the thickness of the brass. \u00a0 Unfortunately, repeatedly undersizing and expanding the neck can make it brittle due to work hardening. \u00a0 Fortunately, there’s another kind of neck sizing die called a bushing neck sizing die<\/strong> that can minimize work hardening.<\/p>\n

A bushing neck sizing die (see Figure 1) features a separate replaceable bushing inside the die that controls the amount that the neck is sized. \u00a0 Bushings are available in various diameters, allowing you to select one that will squeeze down the neck only enough to hold the bullet (ideally, 0.002″ smaller than the bullet diameter). \u00a0 The downside of using a neck bushing die is that multiple bushings are required for different case thicknesses. \u00a0 In other words, when you change headstamps, you will have to change the bushing if one of the manufacturer’s brass is thicker or thinner than the other.<\/p>\n

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Figure 1 – A bushing neck sizing die (like this one from Hornady) allows you to resize the neck without over working the brass<\/div>\n

Partial Neck Resizing<\/b>
\nThere’s a practice mentioned in many reloading books (including the NRA Guide To Reloading) called “partial neck resizing”. \u00a0 This is accomplished using a regular full-length sizing die that is backed off so that the case shoulder remains untouched during the sizing process. \u00a0 The theory behind this is that a conventional full-length sizing die can be used to resize the neck, while leaving the shoulder and body of the case sized to match the chamber. \u00a0Don’t do it. \u00a0<\/strong><\/p>\n

If partial neck sizing was effective, the reloading equipment manufacturers wouldn’t have to make dedicated neck sizing dies. \u00a0 The problem with partial neck sizing is that even though the die is backed off to miss the shoulder, the body of the die will still resize the body of the case. \u00a0 This causes the shoulder to bulge upward, which actually makes the cartridge headspace length longer. \u00a0 Since the cartridge starts out at the full length of the chamber, partial neck resizing makes the cartridge headspace length too long for the chamber.<\/p>\n

I tried this once with a batch of 7mm Remington Magnum brass for a Thompson Center single-shot rifle, and not one of the resulting cartridges would chamber. \u00a0 You may be able to get partial neck sized rounds to chamber in a bolt action rifle, but if the cartridges are too long, the bolt will be hard to close, and hard bolt closure will cause the lubricant to be forced away from the bolt lugs. \u00a0 This can cause galling and premature wear on the rifle. Partial neck sizing is a bad idea.<\/p>\n

There’s a practical limit for even properly neck-sized cases. \u00a0 After 5 or so reloads, the cases will expand enough to make chambering difficult. \u00a0 When this happens, you should full-length size the cases and start the process over again.<\/p>\n

Advantages of neck sizing<\/b>
\nThere are several advantages to neck sizing including longer brass life (more reloads before you have to scrap the cases), fewer reloading steps, and less trimming of the brass.<\/p>\n

If the failure mode for your full-length sized cases is either splitting, or thinning of the case above the web, you will see much longer brass life if you switch to neck-sizing (especially if you use a bushing die). \u00a0 Cracks and splits occur when the brass case has been work hardened to the point where the metal becomes so brittle that it cracks during firing, resizing, or bullet seating. \u00a0 Neck sizing works the brass less than full-length sizing, and a bushing neck sizer die works the case necks as little as possible. \u00a0 This results in less work hardening, and more reloads without splits.<\/p>\n

When you full-length size, the case’s shoulder is pushed back during the process. \u00a0 When the full-length sized cartridge is fired, the shoulder “blows out” to the size of the chamber, causing the case to stretch. \u00a0 The case does not stretch evenly along its full length. Instead, most of the stretching occurs in the case walls just ahead of the web (see Figure 2), which causes the case to become thinner in this area. \u00a0 Too much thinning can result in a full or partial case head separation (the worst kind of failure). \u00a0 This thinning will often appear on the outside of the case as a bright ring, bulge, or crack just ahead of the rim of the case.<\/p>\n

When you neck size, very little case stretching occurs, so the case walls do not thin out. \u00a0 Also, since there is less case stretch, you will not have to trim as frequently (or at all) when you neck size. \u00a0 Another benefit of neck sizing (with a neck sizing die) is that you do not have to lube the cases prior to resizing them. \u00a0 This eliminates two reloading steps: Lubing the cases, and removing the lube after sizing.<\/p>\n

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Figure 2 – A cutaway of a cartridge case showing thinning above the web (indicated by the white arrows) caused by case stretch. \u00a0 This can be virtually eliminated by neck sizing the cases<\/div>\n

Disadvantages of neck sizing<\/b>
\nAs stated earlier, you cannot use neck-sized ammo in any firearm other than the rifle that last fired the case. \u00a0 If you have several rifles of the same caliber, you have to take care to keep the neck sized ammo clearly marked as to which rifle can fire it, and keep it separated from the cartridges of the same caliber that are full length or neck sized for a different rifle.<\/p>\n

You may also find that your neck sized ammo produces larger groups than identically loaded full-length sized ammo. \u00a0 If this is the case, it is likely caused by something being non-concentric. \u00a0 Looking down the bore of your rifle from the breach, your rifle’s chamber (and the ammo you fire in it) consists of a series of lined-up circles. \u00a0 There’s a large “circle” in the chamber where the body of the cartridge goes, another one for the shoulder, another for the neck of the cartridge, as well as smaller circles that make up the leade (the unrifled portion of the chamber with the same diameter as the bullet) and the rifling itself. \u00a0 In a perfect chamber and barrel, all of these circles would be perfectly round, and would \u2018line up’ so that a line through their centers would be perfectly straight and centered in the bore. \u00a0 Unfortunately, there is no such thing as a “perfect” chamber and barrel. \u00a0 Even a carefully machined chamber and barrel will have some (maybe barely measurable) non-concentricity, and some rifles are much worse than others.<\/p>\n

Even if you were in possession of a one-in-a-million concentric barrel, you still have to worry about the ammo. \u00a0The same “circles” that are supposed to line up in the chamber exist on the ammo that you will be firing. \u00a0 The rim must be concentric with the body, which has to be concentric with the shoulder which should be concentric with the neck. \u00a0 In addition, any brass thickness variation within the case itself affects concentricity, as does the bullet seating angle. \u00a0 Of all of these factors, the bullet seating angle probably contributes the most to non-concentricity – especially if you’re not using a competition seating die.<\/p>\n

A full-length sized cartridge has a slightly looser fit in the chamber than a neck-sized cartridge. \u00a0 This extra clearance exists everywhere except for the fit between the outside diameter of the bullet and the inside diameter of the neck.\u00a0 By having clearance everywhere else on the cartridge, the bullet entering the neck can self-center, acting as a pilot to align the rest of the cartridge with the center of the bore.<\/p>\n

With a neck-sized cartridge, very little clearance exists between the case and the chamber, which minimizes the ability of the bullet to center itself in the neck. \u00a0 If enough non-concentricity exists, the bullet can be shoved hard against one side of the neck when the cartridge is chambered, resulting in reduced accuracy.<\/p>\n

The bottom line is this: Using a neck sizing only die for bolt action rifles will increase the life of the brass. However, it can also result in reduced accuracy. If you have a sufficient inventory of brass, full length sizing can provide more accuracy. Use of a brass annealer can aid in achieving longer brass life while full length sizing.<\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

Rifle Cartridge Neck Sizing By design, when a bottle neck case is fired, it briefly expands to fill the entire chamber, then contracts slightly when the pressure generated by the burning powder dissipates, allowing the case to be extracted from the rifle. \u00a0 This is mostly due to the type of brass used for making<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"_links":{"self":[{"href":"https:\/\/www.floridareloading.com\/index.php\/wp-json\/wp\/v2\/posts\/357"}],"collection":[{"href":"https:\/\/www.floridareloading.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.floridareloading.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.floridareloading.com\/index.php\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.floridareloading.com\/index.php\/wp-json\/wp\/v2\/comments?post=357"}],"version-history":[{"count":6,"href":"https:\/\/www.floridareloading.com\/index.php\/wp-json\/wp\/v2\/posts\/357\/revisions"}],"predecessor-version":[{"id":365,"href":"https:\/\/www.floridareloading.com\/index.php\/wp-json\/wp\/v2\/posts\/357\/revisions\/365"}],"wp:attachment":[{"href":"https:\/\/www.floridareloading.com\/index.php\/wp-json\/wp\/v2\/media?parent=357"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.floridareloading.com\/index.php\/wp-json\/wp\/v2\/categories?post=357"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.floridareloading.com\/index.php\/wp-json\/wp\/v2\/tags?post=357"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}