Annealing BPCR Case Necks
By Wayne McLerran
2/3/2021
Annealing is essentially the opposite of hardening. Steel is hardened by raising its temperature to a range that allows the grain structure to be altered, which is then “frozen” by quenching (rapid cooling). If the steel is reheated to a high temperature and allowed to slowly cool it will be annealed or softened. Steel can be hardened or softened by using heat but brass is different and can only be hardened by “work-hardening” (stressing the grain structure) and only softened by applying heat. Reforming, resizing and simply shooting will work harden cartridge brass. By the way, if you hear or read that quenching hot brass will harden it, don’t believe it and question anything else from the same source.
Prior to annealing BPCR cases, I had “hand annealed” high power smokeless bottleneck case necks and shoulders. The smokeless bottleneck cases were annealed to eliminate neck and shoulder case-hardening resulting from full-length resizing after repeated firings. Annealing is also commonly utilized to soften case necks and shoulders when reforming (converting) brass to use for a different cartridge. Since I use fire-formed straight-wall BPCR cases and finger seat (slip-fit) bullets with very little or no neck tension, I’d never considered that annealing the necks was beneficial. But during BPCR reloading discussions with a very experienced shooter, he convinced me to try annealing. He’d experienced some problems with his reloads several years ago. He was seating the bullets with neck tension and did some testing indicating the problem was variations in neck hardness which annealing will eliminate. But at the time he didn’t believe annealing was necessary with slip-fit bullets. Later, additional testing confirmed that variations in neck tensions, even with slip-fit bullets, directly resulted in measureable changes in muzzle velocity and bullet impact vertical dispersion. After annealing the variation disappeared and accuracy improved. Although finger-seated bullets are loaded without significant neck tension, when fired and obturation occurs, annealing will help mitigate the negative effects of inconsistent bullet release due to hard necks.
After annealing a large number of used cases for the 1st time, a neck expander was used to check the neck ID of the fire-formed cases. The slight resistance felt with the expander was very uniform and consistent from case to case. Prior to annealing, even after using the neck expander, the resistance varied from case to case, which was also felt when finger seating bullets. Many BPCR shooters reload with some neck tension and annealing is recommended on a regular basis. Some experienced shooters anneal after each firing as a normal part of their reloading process. Annealing is also recommended when initially using Starline brass, which has the reputation of being harder than Remington or Winchester brass. Another sign that annealing is needed is when cases come out of the chamber with dirty necks indicating the brass did not expand sufficiently or fast enough to seal out gas and fouling blow-by or blow-back. Finally, if accuracy falls off for no apparent reason after firing the cases a few times than annealing may be in order.
Various techniques have been used to anneal brass while protecting the case head, including but certainly not limited to the following. Dipping the necks in oil then for a few seconds in 800°F melted lead. Standing the cases up in a pan of water with the necks above the water, then heating with a torch until the necks turn blue and tipping the case over in the water to cool. Holding and turning the case with pliers or an electric drill with the neck in the flame of a torch then dropping the case in a pan of water. Anneal until the necks glow red will result in damaged brass because the temperature is well above the annealing range and the brass becomes too soft. Annealing in a dark room until the neck shows the 1st hint of glowing orange is a much better approach and should work fine, but can result in overheating the brass if you’re not careful and paying close attention. The cases should be rotated and the necks heated with a propane torch. Use a drill and hold the case in a standard socket slightly larger than the case. Stop heating when the case neck shows the 1st hint of glowing orange. You can dump them on a wet towel or in water to speed up the cooling process but it's not necessary. Quickly cooling brass will not harden it as it does other metals.
Cartridge brass can be annealed at temperatures as low as 480° to 490°F but will require an extended time (hours) to fully anneal. Even at 600° it may take an hour or more and the complete case would be annealed, not just the neck, resulting in a very unsafe condition. If the head is annealed even slightly, it can fail and blow apart when fired. The solution is to quickly raise the temperature in only the neck area to a range of 700° to 800°F, at which point the neck is fully annealed. Since the high temperature is only applied for a very short duration, typically 3 to 4 seconds, the case heads will not exceed 480° unless the cases are shorter than about 1.5” to 1.75”. By the way, YouTube has several videos on annealing. But be aware, some are clearly misleading and can result in damaging the brass due to overheating.
Hot Sand Annealing
What you will need:
- Some clean playground sand.
- A stove and pot to heat the sand. One of the Lee Precision electric casting pots is an ideal solution.
- A Casting thermometer or digital meter with a thermocouple is used to check the sand temperature.
- Some type of small simple metal stand to place in the pot and cover with sand to the depth of the case necks. One solution is to bend a piece of sheet metal to fit.
You’ll need to experiment to find the preferred temperature, which will likely be around 800°F to 950°F. Once the sand is heated to the desired temperature, stick a case neck down into the sand until it hits the metal stand. Stick another case in the sand and remove the 1st one. Increase the heat if the necks are not getting sufficiently hot as indicated by a subtle color change. Do not leave the cases in very long or the entire case will become annealed and soft, resulting in an unsafe condition when the resulting cartridge is fired.
Salt Bath Annealing
Very similar to hot sand annealing, but rather than sand the process typically uses a mix of Potassium Nitrate and Sodium Nitrite (both are salts). As when hot sand annealing, the salts are melted and held to temperatures in the range of 800°F to 950°F, which are considered low temperatures when heat treating metals. Here’s an excellent video on the process: https://www.youtube.com/watch?v=vwdTaDLz56Q&t=17s
What is required:
- 1 to 2 lbs of Low Temperature salts.
- A stove and pot to heat the salts. One of the Lee Precision electric casting pots is an ideal solution.
- A Casting thermometer or digital meter with a thermocouple is used to check the sand temperature.
- A fixture to partly immerse in the melted salts which will hold cases neck down and allow easy hand insertion and removal.
Suppliers of annealing salts and salt bath annealing kits are listed below under Annealing Equipment Suppliers.
Hand annealing using a propane torch
Prior to purchasing a semi-automatic annealer, the hand annealing process I used consisted of heating the neck of a slowly rotating case with a propane torch in a brightly lit room. The cases were inserted into and rotated with a standard ½” drive 5/8” socket using an electric hand drill. Here’s a similar process: https://www.youtube.com/watch?v=kgD5D0Wzu-c. To ensure the necks reached the correct temperature and were not overheated, Tempilaq, a temperature indicating fluid was used. 750° Tempilaq was applied inside the case necks of a few cases to determine the amount of time to hold the rotating case necks in the torch flame. Once applied it quickly dries. When the Tempilaq temperature is reached it liquefies and typically changes color. When 750° Tempilaq liquefies it changes from a light or medium blue to a dark grayish blue. If it gets very dark or black than you’ve overheated the brass. Once the correct heating duration was determined, Tempilaq was not used with the rest of the cases. By the way, applying 750° Tempilaq to the inside of the case necks was found to be more accurate than applying 650° Tempilaq to the outside of the case just below the necks. After annealing, the case was dumped out of the socket onto a soft towel. Quenching the hot case in water does not affect the annealing process and will not harden the brass.
Notes:
- 750° Tempilaq is very thin and wiping several layers or dabbing it on will normally be required to build up an adequate light blue layer. Fortunately, it dries quickly. After heating the grayish dark residue should dissolve with water if it was not overheated and baked on.
- Per the factory, when using any temperature range of Tempilaq, the key is when it liquefies; not the color change although it should happen simultaneously.
I use Remington cases which are normally annealed shortly after being cleaned in a tumbler with ceramic media. Prior to annealing they are “sparkling” clean inside and out. What I found interesting is when the correct temperature was reached the color change in the necks was very subtle. They did not turn a deep blue or display the vivid colors seen in some photos of annealed brass and in a few of the YouTube videos. It is my opinion that the vivid colors are a result of over-heating the necks or possibly due to oxidizing of the case surface from aging. The following photo displays the before and after annealing results of brand-new Remington, Winchester and Starline brass and is similar to the color change of freshly cleaned brass. The brass was annealed using a carrousel-style semiautomatic annealer. Although listed as .45-90, the head of the Starline case to the right is actually stamped 45-2.6
Damage from over annealing
So, what happens if the brass is over-annealed (over-heated)? Damage can result because the brass becomes too soft and hardness can only be restored by work-hardening. Bottleneck case shoulders can collapse when seating bullets with neck tension and the cases can be harder to extract for the same reason mentioned below for straight wall cases. As long as the base is not annealed, over-annealing the neck is not a dangerous condition but can lead to case extraction problems, case stretching and eventually separation. If the case neck and/or body are too soft the brass will not spring back as much after firing, possibly resulting in “sticky” extraction. The soft brass also has an increased tendency to stretch and will require trimming. Repeated stretching and trimming can eventually lead to case separation. Too soft case necks are also reported to result in less accurate loads, the opposite of what proper annealing is meant to fix.
Although I shoot slip-fitted (finger seated) bullets, based on the uniform neck tension results after annealing, which was very consistent from case to case, I plan on continuing to anneal after each firing and will be using a carrousel-style annealer. By the way, if you plan to anneal short cases less than 1.75”, I highly recommend applying 475° Tempilaq to the base area to ensure the base does not become annealed and quickly dump the cases in cold water to stop the heat from reaching the head. 475° Tempilaq is cream colored and turns clear when it melts at the indicating temperature.
Concerning annealing equipment, prior to recent developments using induction heating one could spend as little as a few dollars to hand anneal or over $800 for a top-of-the-line carrousel-style propane-based annealer. Induction heating is the newest technology being applied to annealing cartridge cases. It’s fast & precise but, with prices up to around $1,100.00, the technology is not cheap. Included in the equipment listed below are four induction units dedicated to case annealing. The expensive units, either propane or induction based, do not guarantee a better result but do provide a level of control and faster processing rate not available with hand annealing solutions. Following is a list of case annealing equipment suppliers.
Annealing Equipment Suppliers:
Hand Propane Annealing Kits:
By my way of thinking these are a solution to a nonexistent problem since a drill & socket, which you likely already have, and a bottle of Tempilaq works just as well if not better.
Note: A propane torch is not included with the following solutions.
Although no longer available, the Meacham Tool & Hardware, Inc. sold the “A Deal to Anneal” case holder that mounts in a drill to spin and dump the case after the neck is properly heated.
Enterprise Services, LLC, http://www.cartridgeanneal.com/
Anneal-Rite II Cartridge Case Annealing Unit. Comes with three stands and one case holder.
Although no longer available, The Woodchuck Den (http://www.woodchuckden.com/) was selling the Series II Annealing Tool, also known as “The Ring of Fire” for several years to bench rest and varmint shooters to increase the accuracy potential of their ammo. It’s a neat tool that attaches to a Bernzomatic torch for uniform neck annealing without the need to rotate the case. You can either hold the cases individually with pliers or stand them up in a flat pan with the bases covered with water.
Salt Bath Annealing Kits & Supplies
High Temperature Tools & Refractory, http://www.hightemptools.com/salts.html
A supplier of annealing salts.
Ballistic Recreations, http://ballisticrecreations.ca/
Salt bath annealing kits and supplies.
Automatic Propane Torch-based Annealers:
These are certainly expensive but provide a level of control and faster processing rate not available with hand annealing solutions. Note: Propane torches are typically not included.
Giraud Case Annealer (Giraud Tool Company, Inc),
https://www.giraudtool.com/giraud-cartridge-case-annealer.html
Designed for volume annealing, using a propane torch assembly, the automatic case feeder can handle several hundred .17 cal. to .50 cal. cases at a time by only changing the feeder wheel disc and transfer plate, a 2-minute task. See the unit in action at https://www.youtube.com/watch?v=tCWni2nNNeE.
Annealeez Annealer, http://www.annealeez.com/
Somewhat similar to the larger volume and more expensive Giraud Case Annealer, but on a smaller scale, the Annealeez annealer is an economical solution designed to automatically process a large number of cases. The standard unit will handle .223 to 30-06 cases. Optional indexing wheel kits are available that can handle cartridges as small as 17 hornets and as large as 338 Lapua Magnums. The simplicity of the design and price is appealing and this is the unit I would purchase now if I did not already own the Vertex Bench-Source annealer discussed below. To view the Annealeez in action and other related videos, go to: https://www.youtube.com/watch?v=VKZnwnkkDtc
Sagebrush Annealer, https://www.sageoutfitters.com/cproduct/79/sagebrush-annealing-machine
The Sagebrush annealer is a simpler design and does appear to do the job. The one disadvantage, and I consider it a major shortcoming, is the inability to control speed. The only heating control is the torch position & flame adjustments, which is a drawback when setting it up for different cartridges. If you've tried to precisely adjust the flame of a propane torch you know what I mean.
Bench-Source Annealer (Vertex Manufacturing), http://www.bench-source.com/id81.html
The model comes with a shell or carrier plate that fits up to the largest magnum cases. It can be ordered for .50 BMG caliber or later upgraded with a .50 caliber carrier plate. Using a different technique than the other brands, the shell plate stops and the case spins while being heated. Although the unit is setup to use two torches, only one is generally necessary due to the unique design. The designer and owner is David Dorris.
Note: Buffalo Arms (www.buffaloarms.com) and Graf & Sons now sell the Bench-Source unit.
After considering the other brands available at the time, this is the unit I purchased and highly recommend. The design is well thought-out and the construction is excellent. It has all the features required plus some; comes with an excellent user’s manual and is comparatively priced. By the way, the carrier plates shipped with the current units have an additional set of smaller holes in line with the larger holes which are not displayed in the photo below. They are for smaller cases such as .223, .222, Fireballs, Hornets, Bees etc. And for those of you that are curious as I was, the very small holes closer in to the center in the photo below are used for manufacturing, not for very small cases. Here’s a good video on the unit: https://www.youtube.com/watch?v=0vdRxwcBNP4
AGS Brass Annealer, https://agscustomparts.com/product/ags-brass-annealer/
Made in Serbia, the AGS annealer is the new guy on the block with a nice reasonably priced unit. At 6” X 6” its footprint is the smallest of all the semi-automatic annealers. Included are two sets of interchangeable inserts for different size brass. The website indicates it’s powered by a Wall charger – 12V DC 5.5mm – 2.1mm, 2A, but the power cord is not included due to differences in outlet configurations. I assume the comment is due to differences in USA and international outlets. Following are a couple of YouTube videos showing the unit in operation: https://www.youtube.com/watch?v=v2BtAG0RqRw, https://www.youtube.com/watch?v=Xa6UlH4cIZs
Home Made Annealer
For those of you that are handy making stuff, see the following YouTube video link for the details on how to make a nice unit for $100 or less: https://www.youtube.com/watch?v=k0xE-6bSwME
Here’re some examples of prototype propane torch-based automatic annealers:
https://www.youtube.com/watch?v=Jv75-9p9yFA
https://www.youtube.com/watch?v=9TMe5qcYILM
Induction Annealers
Utilizing the same technology used in electromagnetic induction heating kitchen cooktops, induction brass cartridge case annealers are a relatively recent development. Currently they are more expensive than propane torch-based annealers, but offer some benefits. By controlling the power and timing, very precise and repeatable temperatures can be applied to each case neck, eliminating the risk of overheating the case.
Annealing Made Perfect (AMP) Induction Annealer, http://www.ampannealing.com/
The unit was announced at the 2015 SHOT Show. Currently at a retail price of $1,099.99 plus shipping from Graf & Sons, the USA distributor & reloading equipment supplier. Each case is hand inserted using the correct pilot and standard shell holder.
Annie Induction Annealer (Fluxeon), http://www.fluxeon.com/Annie.html
With over 1000 watts of induction heating power, a typical case can be annealed in around 3 seconds. Cases are inserted by hand. The unit is currently priced at $484.00 + shipping.
Here’re some examples of prototype induction annealing setups:
https://www.youtube.com/watch?v=Ny0a72_AX0E
https://www.youtube.com/watch?v=EGfGV8xrfak
Wishing you great shooting,
Wayne