Annealing in a "nut-shell"
After initial success with "you tube-novice-style" reloading, my tight groupings opened. A friend suggested annealing. It entailed running the cartridge-necks with a handheld drill through a gas flame. I did it in a dark room and released the cartridges in water once the necks turned "cherry-pink".
I must say, despite "overcooking" it thoroughly it worked wonderful and an annealing-believer was born. Fortunately due to my association with weapon clubs, I received more insight into the situation, thus saving me from the "cherry-pink-method".
What happens when annealing? With each firing, the case-neck hardens to a point where it eventually will start splitting. The result is irregular neck-tension and irreparable damage to the cartridge. Neck-tension is paramount to accuracy. Once the neck hardens, expensive presses, bushing dies and mandrills will do little to save the day. Annealing softens brass and returns it to its original properties. Except for the desired improvement in accuracy it hugely prolongs the cartridge life.
At what temperature does brass anneal? The available literature indicates a range of 343Cᵒ-400Cᵒ (650 Fᵒ-750Fᵒ) for rifle cartridges. In this "case", faster is better. Brass is an excellent conductor of heat. The longer it takes, the bigger the chance that the case-head (bottom rim-part) also anneals. The case-head must not anneal as it will be unsafe. Luckily, the "FLAME-ON" process runs super-fast and safe, should you stay within the guidelines.