Reading Your Spent Cases – Learning to Be Your Gun’s Best Friend

Match Grade M1 Garand in 30-06.

Match Grade M1 Garand in 30-06.

The last post we had on the Arts of the Fusilier talked about the need to clean your cases, and it mentioned making them nice and shiny with the appropriate shooting specific case polish.  You can do this strictly for bragging rights about your Beautiful Handloads, or you can do it to make reading your cases easier.  What do we mean by reading your cases?

Well there is the obvious one that refers to headstamp information.  The case head is NOT the bullet end, that’s the case neck!

OK if that’s the neck it wouldn’t it make sense to refer to the bullet as the head?

Hell no, this is English we’re talking here so it won’t necessarily make sense.

So that being settled, the case head is the end with the stamped information on it, it is the thickest portion of the case and it is responsible for holding the primer, and mechanically providing a mechanism for extraction, either a rim, or rimless extraction groove.  Stamped on the bottom of the cartridge is some information about the cartridge, in this case referred to as the “headstamp.” On US small arms military ammo the headstamp usually includes only the manufacturing location (arsenals or factories) and the year of manufacture. Occasionally there are other designations as well such as “NM” for National Match.  Commercial cases typically have an indication of caliber and manufacturer, but not necessarily.  OK enough!

HeadStamps

For our purposes, the information stamped there is for use in separatinge our brass into lots and to keep track of them.  If you’re really into identifying and decoding, this link is really good CartridgeCollectors.org.

But for all of that, this isn’t what we are talking about when it comes to reading your cases, what follows, is.

You can tell a lot from the cases, for instance in the above image the two LC 67 are military once fired cases.  They still have their original brass colored primers and they still carry their crimp on the primer pockets found only in military rounds.  The other two are commercial cases that have been fired at least twice as they carry chrome plated primers which shows that they have been reloaded at least once. Notice also that there is no crimp (that depressed ring around the primer on the LC 67).

The next picture shows a whole bunch of tired 7.62 x 51 NATO (Yeah they’re US manufacture but that’s the official cartridge designation) military cases. In civilian life they are referred to as .308 Winchester.

They all feature silver looking primers so they have what?????

Been reloaded at least once!

Right!  Take my word for it it’s been more times than that, but we will be looking at the bases and the condition of the primers here.

First we can see that this is a mixed bag of ammo lots. This means they will all shoot slightly differently and thus were loaded as “Plinking Reloads” not for serious competiton.  None the less, we see some really nice rounded edge primers in the lower left opposite my thumb.  This indicates moderate pressure loads which fired as expected.  You want to see primers that look like this in your fired rounds.

308headsThe rounds up by my knuckles, the WRA 68, WRA 67, FC 62, and WRA 68 are all showing somewhat flattened primers which indicates a high pressure condition.  The three cases in the detail below also exhibit what is referred to as cratering, where the material from the primer actually flows back along the firing pin creating a lip around the firing pin depression.  This indicates the beginning of a dangerously high pressure condition.

crateringSo if these were your reloads, you might want to re-examine your load data to find out if this was an overload situation. On the other hand if these were long distance (1,000 yard) loads and you KNEW you were pushing the envelope, well, it’s your face after all right?

It just so happens that these cases have yet more to tell us about this, so lets look further.

If you recall, I had mentioned that cleaning cases is about more than simply making things all shiny.  It helps you analyse certain problems like the ones below, these are called case neck splits. If your cases are all dirty, they will be particularly so around the case neck region from blow back gasses that escape during ignition. Without close examination you might have missed these case failures particularly the one on the left.  Cleaning on the other hand makes them stand out.

CaseNeckCracks

Clearly these cases are at the end of their life.  They should be flattened and tossed into your scrap brass box for sale to your local scrapper along with all your spent .22 cases and old keys,  Brass today sells for between $2.47 and 2.85 a pound, so you can save up and buy some 4895 powder pretty quick at that rate!

So my case necks split, so what does that mean.  Well it could be that these cases have been reloaded too many times, it can also be that the brass in the necks of these cases which were reloaded back in 1988 (24 years ago) actually age hardened.  Brass becomes brittle the more it is worked, it has to do with the crystalline structure of the metal itself.  But brass that is deformed and remains under stress (stretching from having the bullet inside the tight neck) can also make the brass brittle over the years.  Lastly, and this one I only found out last night, as certain double based powders age (in this case 4895) they can outgas nitrogen oxide which can also react with the brass in the case neck (the thinnest part of the case) to cause brittleness.

So how do we figure this out?  So many options and so many issues here.  Was it pressure related case neck splits? Work hardening splits? Or, was the powder rotting out my cases from the inside? Lets read further…

HeadSepRingSee that nice ring just ahead of the case head, well that tells us, if nothing else did to this point, is that these cases are way too tired to ever see the light of day again.  If fired and reloaded again these cases would in all likelihood be very prone to failure with a case head separation. Every time a case is fired, it expands to tightly fill the chamber and after the bullet leaves the muzzle again it shrinks back down a bit for easy extraction.  When we reload the case we resize the case back to factory specs for ease of feeding (semi auto – full length resizing). Eventually this process hardens and thins the case just ahead of the head web. What you see above is the result. What would follow next is that the case would separate right along that bright line.

The conclusion after reading all the brass is that these cases are old and tired, and just like the author they have stiffened further with age! Further IMHO the hardening and lack of resilience also contributed to higher pressure in some instances (necks not releasing or corrosion from N_Ox inhibiting release) which exhibited itself in the flattened and cratered primers.

Just for giggles I’ll try to cut some cases and deconstruct some similarly aged rounds for some forensic investigating.  Stay tuned, more to follow!  Hope you enjoyed reading those cases.

Here’s the Article on Head Separation, “That Bright Ring – Incipient Case Head Separation”

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About Gary L. Miller

I have many hobbies and spend a fair amount of time playing at them. I'd love to spend more, but there's this earning a living thing... So I often fill my idle hours spewing forth ideas and opinions, unsolicited or not. This is merely an extension of that propensity.
This entry was posted in Reloading for the Rifle!, The Arts of the Fusilier and tagged , , , , , , . Bookmark the permalink.

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