Annealing brass softens the neck and shoulder of a cartridge case by heating it to around 750°F, reversing the hardening that builds up each time you fire and resize. This restores consistent grip on the bullet, extends case life, and improves shot-to-shot velocity uniformity. For reloaders, it’s one of the most effective ways to keep brass performing like new across many firing cycles.
Why Brass Gets Harder Over Time
Every time a cartridge fires, the case expands against the chamber walls. When you resize it back to spec, the neck and shoulder are physically compressed. Both of these events are forms of cold working, meaning the metal is deformed without reaching a high enough temperature to change its internal structure. Even during firing, the brass doesn’t hit the roughly 600°F needed to trigger any softening on its own.
At the microscopic level, cold working creates more grain boundaries inside the metal. More grain boundaries mean a harder, stronger material. That sounds like a good thing, but in cartridge brass it creates a problem: the neck becomes increasingly stiff and brittle with each reload cycle. Stiff necks grip the bullet inconsistently, and brittle necks eventually crack. Without intervention, most factory brass will develop neck splits somewhere around 10 to 12 resizing cycles. Annealing resets the clock.
What Annealing Actually Does to the Metal
Annealing is a controlled heat treatment that triggers recrystallization. When brass reaches the right temperature range (roughly 500–750°F at the neck, depending on time and method), the distorted grain structure from cold working reorganizes into fresh, smaller, more uniform grains. The metal becomes softer and more ductile, essentially returning to something close to its original factory condition.
Standard cartridge brass is a 70/30 copper-zinc alloy (70% copper, 30% zinc). Research on this alloy shows that recrystallization begins at temperatures around 225–325°C (roughly 440–620°F), with the exact onset depending on how much cold work the brass has received. Brass that’s been heavily worked begins recrystallizing at lower temperatures and shorter exposure times than brass that’s only been lightly stressed. In practical reloading terms, heating the neck and shoulder area to about 750°F for a few seconds is the widely accepted target.
The critical rule: no part of the case should ever reach 950°F. At that temperature, the brass over-anneals and becomes too soft and weak to safely contain chamber pressures. The case head, rim, web, and primer pocket need to stay as hard as possible, which is why annealing targets only the neck and shoulder while keeping heat away from the base of the case.
Consistent Neck Tension and Better Accuracy
Neck tension is the friction grip the case neck applies to the bullet. It determines how much pressure builds inside the case before the bullet releases. When neck tension varies from round to round, bullet release is inconsistent. Inconsistent release means inconsistent muzzle velocities, which show up as vertical spread on target.
Work-hardened brass develops uneven neck tension because different areas of the neck may have been stressed differently across multiple firing and resizing cycles. One side of the neck might be harder than the other, or cases within the same batch might vary widely. Annealing resets all of this, bringing the neck and shoulder area back to a uniform, controlled state so each reload behaves more like the first firing. Competitive precision shooters chase single-digit extreme spread (the gap between the fastest and slowest round in a string), and consistent annealing is a major factor in achieving that.
Longer Case Life
Without annealing, brass accumulates work hardening until the neck cracks. Factory semi-hard necks typically last around 10 to 12 resizing cycles before splitting. Annealing after every firing cycle (or every few cycles) prevents the neck from ever reaching that failure point. Reloaders who anneal regularly report well over a dozen firings on the same brass with no neck or primer pocket failures. At that point, the case head or primer pocket usually wears out before the neck does, which means you’re getting the maximum possible life from each piece of brass.
For anyone shooting premium match brass, where individual cases can cost $1 or more, doubling or tripling case life is a meaningful return on the time annealing takes.
How to Tell If You’ve Done It Right
The most reliable visual indicator for torch annealing is a very dull red glow at the case mouth, observed in a darkened room. This glow corresponds to what’s called the Draper point, the temperature at which metals begin emitting visible light. For brass, that’s approximately 800°F, plus or minus about 50 degrees. Even in industrial brass flame-annealing settings, this visual cue combined with time is the standard way to control the process on thin brass.
The key word is “dull.” You’re looking for the very first hint of color. If the brass turns orange, you’ve gone too long and risk over-softening. Temperature-indicating lacquers (like Tempilaq) offer another approach. You paint the lacquer onto the neck before heating, and it melts at a specific calibrated temperature. Some reloaders find the results hard to interpret, especially because the lacquer sits on the outside surface and can be directly hit by the flame, potentially reading high. Infrared thermometers are a third option, though the speed at which thin brass cools makes timing the measurement tricky.
Whatever method you use, the safety guideline is straightforward: the neck and shoulder should reach at least 750°F, and the case body below the shoulder should stay under 450°F to prevent softening in areas that need to remain strong.
Annealing Methods Compared
The three common approaches are propane or butane torch, salt bath, and induction.
- Torch annealing is the most accessible. You spin the case in front of a flame for a set number of seconds, then tip it into water. The challenge is consistency. Flame temperature varies, hand speed varies, and judging that dull red glow takes practice. Some reloaders describe it as more art than science, noting uncertainty about whether they’re actually annealing, doing nothing, or damaging cases.
- Salt bath annealing uses a pot of molten salt held at a precise temperature (typically 500–550°C). You dip the neck and shoulder into the bath for a set time. The brass can never get hotter than the liquid itself, which eliminates the risk of overshooting. The downsides are that it’s manual (hard to automate the dipping), the brass acts as a heat sink that gradually pulls the bath temperature down, and the salt level drops slightly each time brass is removed.
- Induction annealing uses an electromagnetic coil to heat the brass from the inside out. Dedicated machines calibrated for specific cartridges offer the highest repeatability. Slight differences in case position within the coil can cause minor temperature variation, but for most practical purposes, induction delivers the most consistent results. Reloaders using well-calibrated induction annealers routinely report single-digit extreme spread in their velocity numbers.
When and How Often to Anneal
Most precision reloaders anneal every firing cycle, treating it as a standard step in case preparation alongside resizing, trimming, and chamfering. Others anneal every two to three cycles, especially with brass that sees lighter loads or minimal neck sizing. There’s no single correct interval. The goal is to anneal before the neck hardens enough to cause inconsistent tension or approach the brittleness that leads to cracking.
New brass from the factory is often shipped with necks already in a semi-hard state. Some reloaders anneal new brass before its first loading to establish a consistent starting point across the entire batch. This is especially common in competitive shooting, where eliminating any variation from the beginning matters.