A long while back I was writing about how I made a shim to keep cases from hitting my sizing die.

Let me take a step back though to explain what this thing does. For this I need to go back to the gun itself. When you pull the trigger a fire a round an interesting thing happens in the chamber — the case expands. Why? Simple: brass is a very soft metal. Its job isn’t to hold in the pressure of the gun powder. It serves to purposes: hold the un-fired cartridge together and as a seal in the firing process.

The first of these is obvious to anyone that has ever picked up a round of ammunition, the second is less intuitive. While the tolerances in modern firearms are very tight, there’s some huge tolerances in ammunition. Some of the specs allow for a hundredth of an inch in either direction! Yes, I know that sounds small, but it’s actually really big in this case. Even if you could make it a perfect fit, you wouldn’t want to; the moment a piece of dirt or grit got in the chamber you wouldn’t be able to feed another round in.

The upshot is the chamber (where the cartridge sits at the breech-end of the barrel) is bigger than the case. When you pull the trigger the primer ignites the powder and that starts to push the bullet out of the case. At the same time it causes the case to expand to seal the chamber from the hot gasses that are being produced. If this didn’t happen, you would have a lot of blow-back of gasses since the burning powder would try to get around the case and back out the breech-end of the gun — into your face!

So, at the end of that process you have a case that was bigger than it started. So big in fact that it might not chamber a second time. Certainly it’ll be too big to hold another bullet. What to do: resize the case to the original size! That is precisely what this die does.

Well, what was going on is that the Redding die kept jamming things up. The case mouth would hit the die instead of going in and resizing. Perhaps it’s stacking tolerances with the press, shell plate, and die, but regardless the reason it would hang up perhaps a third of the time.

So I decided to try to get another die. I picked up a Lee since they are pretty cheap. Sometimes people seem to avoid them because they are cheap… but I’ve not had any real bad luck with them. Above the Lee die is on the left and the Redding is on the right.

What you can see when looking into the business-end of the dis is that the Lee has a slight chamfer on the edge that the Redding lacks. This is both good and bad. Good since in the 500 rounds I made today I had no hangups. Bad because it doesn’t size the case down as far. But sizing it down that far isn’t strictly needed anyway since the case head doesn’t really grow while things are being fired.

So… there you have it. A $21 solution to an irksome problem.

We came back from the range a week or two ago and with the cases that we’ve fired we seemed to pick up a rogue case.

In sorting En properly picked the 10mm from the pile of .40 that we shot. They are basically the same case, but the 10mm is a bit longer and it uses a large primer to set it off. Looking at it I quickly found something amis with it.

Of course that’s not what a proper 10mm. The jagged edge is a dead giveaway.

Left: Proper fired 10mm case. Right: Recovered 10mm case with a lateral split.

Looking at the primer, while not an exact science, really told the story.

This was shot out of a Glock. I’m going to presume that it’s out of a Glock 20 since I’ve never seen anyone with a 29. You can tell that it’s from a Glock because of the peculiar rectangular firing pin channel. Of course in this instance it actively flowed into the channel and completely flattened itself against the breech face as well.

Even the head-stamp shows a bit of distress.

The 10mm cartridge is really hand loader’s cartridge. It doesn’t have a lot of guns that are chambered for it as well. That being said it is a large-capacity cartridge and you can easily tune the load from a very light load to a real barrel-burner. The Starline brass is another piece of evidence since they mainly cater to handloaders. (I have seen Starline on a commercial loading from Fiocchi in .40 S&W, but I’ve never seen it elsewhere)

Putting the pieces together I can only guess that this particular case was overcharged, perhaps double-charged.

Here’s what it should look like, compared to the blown up round:

The case on the left shows no signs of the primer flowing at all. You can still see the radius at the edge of the primer as well. The head stamp seems significantly clearer as well — though that in and of itself isn’t enough to go on since I don’t have any other examples of what 10mm Starline brass looks like. Incidentally you can tell the good case was also fired out of a Glock, perhaps out of the same one. (I picked up the good case around a year ago; the broken case is from a week or two ago)

Here’s another example of a fired large pistol primer in a different (and lower pressure) case:

I don’t have any unfired factory large primer case, but they look a lot like the small primers.

All of these are from Winchester white box 9mm. Their still in their original case in this picture.

Here’s all of the fired large primers in one picture for comparison purposes.

I just wonder what happened to the gun when this round was touched off. Certainly it left some of itself in the chamber of the gun… How bad was it?

Quick and random one today. When I buy boxes for ammunition they always seem to come with stickers for the load information.

That might work fine for rifle loads when you load up 20 for hunting or something, but it seems to be a bit insufficient for pistol loads when I load up 300 in an sitting (or more!) and I reuse the boxes over and over.

That got me thinking about labels.

At OfficeMax I came across some semi-permanent labels: Post-it Labels

Here’s the template I’m using for them: Load Data Labels

I can tell you that they do go on fine, and just as importantly they come off fine too.

Here’s what I’m recording on each label: Lot Number, Cartridge Type, Powder Type, Powder Amount, Bullet Type, Bullet Weight, Overall Length, Production Date and Notes

All of these are also recorded in my log book (well, Google Spreadsheet), but it provides a great quick reference. (The log also includes things like lot numbers, and a whole bunch of other settings…)