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Reloading: Brass Eternal

Reloading: Brass Eternal

Stand in cold water and blast with a blow-lamp. No, it’s not the script for a new Japanese game show, just a précis of this month’s subject! I really do enjoy handloading and almost all that it entails. However, I must confess that I personally draw the line at trying to make my brass last forever. Case annealing is of course, the topic.

HARD TIMES

Most metals and alloys can be subjected to a process called work hardening. Put simply it means that the material becomes harder and sometimes more brittle as it is repeatedly bent, struck, stretched or chemically attacked. The process can be either beneficial or undesirable depending upon the application and the metal in question. On the plus side, many designs of impact use tools are deliberately work hardened by hammering or shot peening in order to improve their durability. Unfortunately this process is seriously detrimental to cartridge brass.

We’ve already discussed the fact that the cartridge case acts as a gasket, expanding to seal the considerable pressure generated during firing. The better the fit in the chamber and the lower the internal pressure, the less stretch deformation will be required to achieve this. However, this desirable stretch property of cartridge brass (ductility) has a downside as the case does not fully recover to its original size after firing.

The resulting growth in the external dimensions is the reason that we need to re-size before reloading. However, the re-sizer cannot totally restore the dimensions, as part of the deformation process involves an insidious thinning of the wall, usually at a number of primary points. Whilst the sizer can restore external dimensions it can only turn this change into growth in the overall length of the case. The loss of wall thickness is, for all practical purposes, irreversible.

SPOTTING THE SYMPTOMS

This expansion and re-sizing is the process that generates the work hardening. Assuming all other things are equal then there are three ways in which this will manifest itself. The first (hopefully) is a detectable increase in resistance when passing the case through the sizer die, especially if it is being full length re-sized. The second is an increase in extraction resistance on the lever, bolt or ejector rod. The third is often the consequence of a failure to spot the first two… the extracted case has split, usually at the neck or has separated about a quarter to one third up the wall.

The original case manufacturing process involved a brass billet or slug being forced over a series of shaped dies, stamped by press tools, turned, chemically treated and polished. Along the way it was annealed several times. The resilience that we require was restored to the material by the final annealing.

The upper portion of the case body and neck was heated to between 650 and 700º F (345 – 370º C) and then allowed to cool. Where there is a risk of the heat migrating to the case body then it is quenched to arrest it.

DOING THE NUMBERS

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The temperature necessary to achieve molecular realignment is different for every metal and alloy and furthermore, can vary in relation to the application time. A vivid change in colour can act as a visual indicator for some materials but not brass… even faint cherry red is too hot. A slight ‘sparkle’ in the brass and a tone change that has the appearance of a dark stain are the ideal indicators.

PROCESS PROGRESS

The low-tech old timers method of case annealing involves a baking tray at least a couple of inches deep, cold water, sturdy gloves, a propane or butane torch and lots of luck. The de-primed and cleaned cases are stood in the water filled tray with just the neck and shoulder above the waterline. Make sure that the water level inside the case matches that outside. The gas torch flame is played evenly around the neck until the sparkle and tone changes are visible.

This is maintained for at least a minute or so before the case is tipped over. Repeat until the batch is finished. Practise the process on small batches of brass that you were going to scrap… they may now be scrap anyway! Check their properties by tumbling and resizing, remembering to dry them before lobbing them into the tumbler.

Do the necks all require the same pressure through the die? Probably not. The downsides of this process are significant. Controlling the distance of a hand held flame, applying the heat evenly around the neck and establishing an appropriate and consistent heat soak time are a challenge.

AUTOMATICALLY BETTER

Enter the mechanised process. An indexed shell holder turntable with a massive metal heat-sink base, mountings for two, three or even four gas torch jets and a fixed or variable speed drive. Such devices are offered by Ballistic Edge Manufacturing of Rio Medina, Texas. Check out their video web pages:-http://www.ballisticedgemfg.com/model-360.htmlhttp://www.ballisticedgemfg.com/model-400.html

These machines solve the variables introduced by a water and tray method. A multiple heat source not only offers improved regularity but shortens the time needed to achieve the desired level of heat soak. The presence of a large heat-sink obviates the need for water, the treated cases simply dropping into an open tray in order to air cool.

COST V BENEFIT?

Let’s look at the financial viability of annealing. If your calibre and preferred headstamp are available as either loaded ammo or un-primed/primed brass then even the knife and fork annealing process looks marginal. Total the cost of a bottle of butane for every 30 or 40 cases and the time you need to devote to the process. Not good. Automation can add around £400 as an upfront cost for the machinery. This can be amortised over your case annealing program… but if you only treat a couple of hundred cases a year then the added cost will be 20p each for the next decade. Add to this the fact that case wall thinning cannot be reversed, then your brass still has a finite life expectancy.

However, the game changer is the obsolete cartridge. Where the brass is irreplaceable, has to be bought from a specialist machine shop or adapted from another calibre then the annealing process can provide valuable life support.

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