Reloading Basics: Back on the Case
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- Last updated: 01/07/2019
As cases are reused several times, they are worth a bit of further attention. One of the most common questions that anyone new to reloading asks is, “how many times can I reload my cases?”, and it is not a question that has a straightforward answer. Although signs of case wear and tear were considered in a previous article, I have not looked at ‘life expectancy’.
There are a number of factors that have an effect on the lifespan of cases used in reloading. The pressure that the cases are subjected to, the gun the rounds are fired in, the makeup of the cases themselves and the reloading dies used can all have a direct effect on how many times the cases can be reloaded before they fail.
In this article, we are looking at case failures due to ‘wear and tear’, not catastrophic failures due to other factors. Worn out cases become noticeable when the case neck splits or, in some bottle neck cases, a split occurs at the shoulder of the case where it steps down to the diameter of the bullet. Problems with chambering rounds can also be an indication that the cases are no longer viable.
Pressure is the most obvious cause of case failure, as it represents the force that the case is subject to when the round is fired. The case is rapidly expanded to the dimensions of the chamber it is being fired in, held there until the pressure drops down again, and then allowed to spring back to a smaller size (but generally not the same size it was before firing). Fast burning powders generate the pressure quicker and so cause a faster expansion, which is more stressful to the case. Using a slower burning powder, where possible, will extend the life of your cases.
The effect of pressure is closely related to the characteristics of the chamber of the gun that the rounds are fired in. A tighter chamber means that the cases will expand less than if they were in a looser chamber with more room around the case. The difference between a tight and a loose chamber may only be a couple of thousands of an inch, but it does have a big impact of case life. Chamber dimensions are pretty much outside of the control of the reloader; however, if cases repeatedly fail early, it is worth getting it checked out.
In terms of makeup, cases are generally all brass or nickel coated brass. The brass will have been heat treated during manufacture, to give it its springiness but this will generally be lost with repeated use, as the metal is ‘worked’ by the process of being fired. Brass is used in the manufacture of cases because it has the right properties in terms of strength, durability and elasticity. With nickel-plated cases, the plating can often be seen to start to peel away around the case mouth after the first use and, with a couple more uses, it is very clearly coming off. This then leaves a thinner base metal case, which tends to last only around 40% of the life of an all brass case. The brass and the nickel have different properties, so will expand and spring back at different rates and amounts, generating stresses, which cause them to separate and the nickel to peel off. Stick to brass-only if you can, it lasts much longer.
Your dies and, more specifically, how they are set up, will also significantly affect the life expectancy of your cases. In particular, the flaring and crimping operations stress and weaken the case mouths considerably and so should be kept to the minimal amount necessary. Regularly trimming cases to length will remove the most weakened metal at the case mouth and so extend their life.
Resizing cases is another way that cases are stressed, so it needs to be done correctly. When full-length sizing bottle necked cases, it is important to use case lubricant. If you do not, then the compressive and then tensile forces applied to the case will stress it and reduce its life. With 45/70 cases, which although straight walled still need lubricating to size them; if a case is not lubricated properly, the amount of force you have to use to size and then extract the case from the die is considerable and so over-stresses the brass. Also, if you use too much case lubricant, you can cause ‘dents’ in the outside of the case, where pockets of lube are trapped against it. These dents will flatten out during firing but that will cause stress points in the metal, which may then crack. As case mouths become weaker, they can sometimes fail to grip the bullet properly, despite being crimped, and bullets can slip back into the case when the round is chambered, with potentially disastrous results. This is an important sign of case-fatigue to watch out for.
So, back to that original question, how many times can you reload your cases? This varies from calibre to calibre, brand to brand and of course due to the factors listed above. With .357 calibre brass cases, around 30 loadings are possible with light target loads; in the same calibre, nickel plated cases start to fail after less than 10 loadings. In .308 calibre, it is possible to reload 20+ times without case failure but, like with most things in life, this does depend on the quality of the materials you start with. Whenever possible, start off with quality cases, they will last longer and, although more expensive to purchase, they will actually work out cheaper over their lifetime. The life expectancy of 45/70 cases is generally lower, due in part at least to their large diameter and surface area.
As you can see, the answer is indeed far from straightforward, but it is possible to optimise the life of your cases by managing those factors that you can control. It is also important to ‘retire’ batches of cases when they start to fail, rather than continue to use them until one fails catastrophically. Not all the cases in a batch will fail on the same loading, but when the cracks start to appear in a few of them, the rest are sure to follow in quick succession.
Henry Krank & Co Ltd. henrykrank.com
Norman Clark Gunsmiths. normanclarkgunsmith.co.uk
JMS Arms. jmsarms.com
1967 Spud Reloading Supplies. 1967spud.com
Hannam’s Reloading Ltd. hannamsreloading.com
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