Editing Handloading (section)

===Case life maximization===
[[File:Caliper.jpg|thumb|right|Digital calipers for measuring case length]]
Since the case is the single most expensive part of a loaded round, the more times a case can be re-used, the better. Cases that are loaded to a moderate pressure will generally last longer, as they will not be [[work hardening|work hardened]] or flow under pressure as much as cases loaded to higher pressures. Use of moderate pressure loads extends the life of the case significantly, not to mention saving quite a bit of wear and tear on the barrel.<ref>{{cite book|last=Warner|first=Ken|title=Gun Digest 1991|year=1990|publisher=DBI Books Inc.|isbn=978-0-87349-105-1|pages=151–152}}</ref> Work hardening can cause cracks to occur in the neck as the hardened brass loses its malleability, and is unable to survive swaging back into shape during the resizing operation. Rifle brass tends to flow towards the neck (this is why rifle brass must be trimmed periodically) and this takes brass away from the rear of the case. Eventually, this will show as a bright ring near the base of the cartridge, just in front of the thick web of brass at the base. If brass is used after this ring appears, it risks a crack, or worse, a complete head separation, which will leave the forward portion of the brass lodged in the chamber of the gun. This generally requires a special stuck case removal tool to extract, so it is very undesirable to have a head separation.<ref name=nonte_15 />

With bottlenecked cartridge cases, choosing the right sizing die can also be important. Full-length sizing of cartridges is often thought to greatly shorten case life by work hardening the full length of the case, which can cause the case neck to split, although some studies show that the number of reloads possible with a case is essentially the same for either full length sizing as for neck sizing only if the issue is one of neck hardening. If the reloaded cartridges are going to be used in the same firearm in which they were previously fired, though, and if that firearm has a bolt action or other action with a strong camming action on closing, then full-length resizing may not be needed. A collet neck sizing die can be used to size just the case neck enough to hold the bullet and leave the rest of the case unsized. The resulting cartridge will chamber into the specific rifle that previously fired it, though the fit might be tight and require more force to chamber than a full-length resized case. The use of a neck-sizing die in conjunction with moderate pressure loads may extend the life of the case significantly by minimizing the amount of case that is work hardened or stretched. This is especially true for reloads intended for military rifles with intentionally large chambers such as the [[Lee–Enfield]] in [[.303 British]].  The use of partial length or neck sizing for cartridges used in such large chambers permits effectively switching the headspacing from relying on the rim of a rimmed cartridge to the shoulder of the bottleneck transition instead, increasing the number of times a rimmed military cartridge can be reloaded from once to perhaps 5 or more times, all while avoiding dangerous incipient head separations.  One final form of limiting case wear is limited strictly to benchrest shooters with custom-cut chambers. The chamber of these rifles is cut so that there is just enough room, typically just a few thousandths of an inch, in the neck area.  The result of using this type of chamber is that fired rounds do not require any resizing whatsoever once the case is fired.  The brass will 'spring back' a bit after firing, and will properly hold a new bullet without further manipulation. Some refer to this as a 'fitted' neck, however, it is a function of both the carefully cut precision neck and the case adjusted to fit with very little clearance.<ref name=VarmintAl>{{cite web |url=http://www.varmintal.com/arelo.htm |title=Varmint Al's Reloading Page}}</ref>

Work hardening happens to all cases, even low-pressure handgun cases. The sudden increase in pressure upon firing hits the brass like a hammer, changing its crystalline structure and making it more brittle. The neck of the case, if it becomes too brittle, will be incapable of standing the strain of resizing, expanding, crimping, and firing, and will split during loading or firing. Since the case neck remains in tension while holding the bullet in place, aging ammunition may develop split necks in storage. While a neck split during firing is not a significant danger, a split neck will render the case incapable of holding the bullet in place, so the case must be discarded or recycled as a wildcat cartridge of shorter overall length, allowing the split section to be removed.  The simplest way to decrease the effects of work hardening is to decrease the pressure in the case. Loading to the minimum power level listed in the reloading manual, instead of the maximum, can significantly increase case life. Slower powders generally also have lower pressure peaks and may be a good choice.<ref>
{{cite book |title=Complete Outdoors Encyclopedia: Revised & Expanded |author=Vin T. Sparano |year=1998 |publisher=Macmillan |isbn=0-312-19190-1 |page=[https://archive.org/details/completeoutdoors00spar/page/175 175] |url-access=registration |url=https://archive.org/details/completeoutdoors00spar/page/175 }}</ref>

[[Annealing (metallurgy)|Annealing]] brass to make it softer and less brittle is fairly easy, but annealing cartridge cases is a more complex matter. Since the base of the case must be hard, it cannot be annealed. What is needed is a form of [[heat treatment]] called [[differential hardening]], where heat is carefully applied to part of the case until the desired softness is reached, and then the heat treatment process is halted by rapidly cooling the case.  Since annealing brass requires heating it to about 660&nbsp;°F (350&nbsp;°C), the heating must be done in such a way as to heat the neck to that temperature, while preventing the base of the case from being heated and losing its hardness. The traditional way is to stand the cases in a shallow pan full of water, then heat the necks of the cases with a torch, but this method makes it difficult to get an even heating of the entire case neck. A temperature-sensitive crayon can be used at the point to which it is to be annealed, which is just behind the shoulder for bottlenecked cartridges, or at the bottom of the bullet seating depth for straight-wall cartridges. The neck of the case is placed in a [[propane]] torch flame and heated it until the crayon mark changes color, indicating the correct temperature. Once the correct temperature is reached the case is completely quenched in water to stop the annealing process at the desired hardness.  Failing to keep the base of the case cool can anneal the case near the head, where it must remain hard to function properly.<ref>[http://www.gun-tests.com/performance/jun96cases.html Gun Tests] {{Webarchive|url=https://web.archive.org/web/20060218145622/http://www.gun-tests.com/performance/jun96cases.html |date=2006-02-18 }} article on case annealing.</ref>  Another approach is to immerse the case mouth in a molten alloy of lead that is at the desired annealing temperature for a few seconds, then quickly shake off the lead and quench the case.<ref name=nonte_14 />

Cases that have small cracks at the neck may not be a complete loss. Many cartridges, both commercial and [[wildcat cartridge|wildcats]], can be made by shortening a longer cartridge. For example, a [[223 Remington]] can be shortened to become a [[.222 Remington]], which can further be shortened to become a [[.221 Fireball]]. Similarly, [[.30-06 Springfield]] can become [[.308 Winchester]], which can become any number of specialized [[benchrest shooting]] cartridges. Since the cracking is likely due to a brittle neck, the cases should be annealed before attempting to reform them, or the crack may propagate and ruin the newly formed shorter case as well.<ref name=nonte_14 />