why anneal brass

[scastle]

sorry never heard of this, I watched video,what doe it do when it heats up? could some one please explain this to a dumb ol country boy

 

[Engineering101]

For best accuracy you want consistent and relatively low neck tension. It is an unfortunate fact that every time you resize brass you work harden it which messes up neck tension. Eventually you will not be able to force bullets into the neck without crushing them, never mind the effect on accuracy. So you must anneal the brass to reset it to its original malleable state. Some guys anneal after every resizing. I go 2-3 resizes before I anneal.

 

[rcoody]

For best accuracy you want consistent and relatively low neck tension. It is an unfortunate fact that every time you resize brass you work harden it which messes up neck tension. Eventually you will not be able to force bullets into the neck without crushing them, never mind the effect on accuracy. So you must anneal the brass to reset it to its original malleable state. Some guys anneal after every resizing. I go 2-3 resizes before I anneal.

consistent neck tension and brass life

it has to be done right to work

average shooter/reloader would never notice the difference

but if you want to experience what it does take some old cases that have been fired 8 or 10 or more times without annealing and get someone to anneal half of them. then reload the annealed and unannealed cases. Of course keep them separated. You can certainly feel the difference on bullet seating and I can feel it during the resizing process.

you will see the difference on the range in group sizes with a truly accurate rifle.

 

[Beng]

Everytime you fire your brass, it gets pressed against the chamber walls and stretched a little bit, so you have to resize it. The stretching and resizing changes the metals microstructure slightly, deforming the brass grains (the smallest chrystal units inside a metal) and allowing small lines of defects in the structure (dislocations) to grow and make it harder for the metal to deform. This makes the brass stronger and less flexible. At some point the brass gets so inflexible, that it can't even be stretched to the chamber walls, that usually support the brass against the pressure of the powder gases. Without this support the brass isn't strong enough to withstand the forces which the gases enact upon it and ruptures. This is how split necks form.
If you heat the brass to a certain temperature before it splits, the brass grains reorganize in a new chrystal structure and and reduce the amount of disllocation defects in the microstructure, making the brass flexible again.
Look up work hardening and dislocation in wikipedia, if you want to know a little bit more.

 

[918v]

New cases as they come from the factory are annealed for optimum hardness. This level of hardness enables the case neck to have the right amount of springback to hold on to the bullet. This serves a two-fold purpose: it makes the cartridge sound so you can load and unload it without it coming apart, and fosters uniform combustion of the powder. If the necks are too soft, they will not have any springback. If you seat a bullet into a neck with no springback all that will happen is the bullet will expand the neck and then fall out. This lack of grip also destroys combustion uniformity and ruins accuracy. I always know when I overcooked the necks when the accuracy goes to hell. It turns a half inch load into a two inch load every time. And the extreme spread quadruples. When you anneal, you have to do it right. After annealing my brass using a variety of torches, I have come to a conclusion that none are precise enough. Their flame length varies as does the temperature due to heat soaking of the tip. If you search YouTube you'll run across a video of Norma factory brass production. If you pay attention closely, you'll see their annealing process. They use a long and wide torch head with a series of small flames. The cases pass through the flames at a certain speed and are annealer uniformly. It is far easier to control a small flame than a large one. The best solution for the home annealer seems to be to use two torches with a pressure regulator, preheating, and minimizing the dwell time of the brass. Induction annealing is the most precise method, having the ability to control the dwell time to a milisecond. But it's also very expensive at this point.

If you don't anneal, every time you fire/reload the neck gets harder and the springback increases. This affects bullet seating/bullet release but you can compensate for it with specialty dies having the ability to adjust neck dimensions. After several cycles, however, the neck gets too hard and fails.

Now, depending on your load, the primer pocket may fail long before the neck does. So whether annealing will benefit you will depend on a variety of factors.