|Why do we want to anneal brass cartridge case neck? Short answer, prolong brass life and improve accuracy. Fire a round and the case neck expands in the chamber neck area about .010”. Resize the case reduces the diameter. Next the neck is expanded to receive a bullet. Finally, upon bullet seating the neck expands a little more. All of this case neck flexing introduces work hardening stresses which are removed with proper annealing. Without proper neck annealing cases will normally start failing with cracked necks after 5 to 7 firings. A test was conducted to determine case failure rate, 10 quality .308 Win. cases were fired then reloaded without annealing the necks. The first failure came at 5 firings. The balance of the cases was kept in the trial, after 10 firings a couple were left revealing wrinkles and signs of impending failure and were scrapped. |
Let’s take a close look at properly annealing cartridge brass necks, we didn’t say annealing cartridges, loaded rounds, this must never be attempted. In the case of bottle neck cases also annealing a little way down the shoulder. One fact must be clearly understood, the head of the case, the base where the extraction groove or rim is located must never be annealed. The case head is work hardened in the manufacturing process resulting from blanking, drawing and shaping the case and it must remain as is. Preserving the hard case head is for safety, some center fire rifle cases operate as high as 65,000 PSI. A number of pistol cases also attain high pressure upon firing. For example; 9 mm Luger & .357 Mag. develop 35,000 PSI, 10mm Auto 37,500, .454 Casull 65,000. Annealing pistol case necks is beneficial. The Anneal-Rite unit, when carefully operated, successfully anneals 9mm Luger cases without annealing the head. This is quite beneficial for .357 Mag. .45 Colt and .44 Mag cases as the mouth gets belled out to receive a bullet and then crimped in, lots of work hardening here.
The case head must be left in the factory hardened state to prevent it’s rupturing and releasing high pressure gas. If a blowout occurs from case head failure, it would likely wreck the firearm and quite probably injure the shooter.
What kind of accuracy is attainable anyway? One session at our local range had great weather, overcast sky, very light wind in line with the target. Best group this day was .620” – 5 shots at 300 yards. The rifle used was a Remington 700, standard SAAMI .308 Win. chamber, Rock Creek barrel and a Jewel trigger, action glass bedded. This is not a $3,000.00 Benchrest job, just a tuned-up gun with standard SAAMI chamber.
Today the cost of brass has dramatically increased. Some exotic stuff like .500 NE or .505 Gibbs cost $5.00 ea., .338 Lapua Mag. $3.40, premium .308 Win. $1.50 ea. By annealing the neck of cases, you greatly increase the life and improve accuracy due to consistent neck tension. Current testing of 50 quality .308 Win cases is underway, the next reloading will be the 21st time fired in the aforementioned rifle. This batch of brass will have fired over 1,000 bullets downrange yielding a dramatic savings, and it’s still going strong. This batch of brass is neck annealed after each firing, it’s been full length resized once, neck sized every firing and trimmed when needed. So brass neck annealing really pays off and the Anneal-Rite brass annealer rig is super cost efficient. This unit is provided with 750º F Tempilaq for precise temperature control.
A major brass manufacturer stated their procedure is to anneal at a minimum of 700º and not over 800º F. See the demo video at www.cartridgeanneal.com, its guaranteed to give perfect annealed necks, easy-to-follow directions provided.
Tom Wilson 8-26-23©