February 25th, 2023
Close-up view a sectioned case. Glen Zediker observed that this one was “fixin’ for pop”. Here are highlights of an article Glen Zediker wrote about the Midsouth Blog. Glen Zediker, who unfortunately died in 2020, wrote that article about cartridge brass. Glen identified the most common failures in brass that has been fired at high pressures or multiple times. Glen outlined some simple methods to check your cartridge brass for “early warning signs of case failure”, particularly case head separation. This can be very dangerous. Glen is the author of many great books on reloading. This article is adapted to two Glen’s books, Handloading for Competition and Top-Grade ammo. Glen Zediker – How Cases Degrade With Multiple Firings
This article will explain when and how to monitor the progress of changes that begin with the firing of a new case. It’s called the “progress in degeneration” because it is a way to look at it. The concern is getting a handle of when enough change has occurred in the brass that requires attention. Or abandonment. For me, that means 4 firings. As I mentioned last time, this is when I might notice changes that need attention. As I said, this figure was not a random number. It was calculated from my own notes when running competition NRA High Power Rifle loads. [Editor’s note: We typically get 10 good firings with Lapua brass when we use moderate loads in bolt-action rifles. However, Lapua brass can be annealed and run at low pressures for up to 20 load cycles. The case neck and the case head area are most affected. The case neck walls become thicker, but the body walls of the case head area get thinner. Primer pockets become smaller and more narrow. This case shows a cracked neck and a crack (separation above the case head). Zediker states that it is rare to see a case with both of these most common failures. An M14 attacked this case. “Case head — Causes of Separation or Cracking
Brass, like water, flows when it is put under pressure during firing. The chamber steel limits how much it can expand. The bolt face is pressed against the bolt base, and the case shoulder moves fully forward. It is as if there is a tug on both ends. It gets stretched. The shoulder area can expand to conform to the chamber relatively easily, but the case head, which is more difficult, is not. Because it’s the part of the case with thickest walls, it doesn’t expand much. It does, however, stretch. The “case head area”, as I refer it here, is the area of the case above and below the web. This is just above the taper that leads into the extractor groove. The “area” extends approximately eight inches up the case body. Here’s a pressure ring. This will be visible after firing, if it is visible. If you can see it, the case is closed. The bright ring is indicative of excessive stretching, which can indicate excessive thinning. If you see a ring around the case, which is noticeable because it’s lighter than the body, and it’s in the area, it’s likely that the case has been closed. This is the place where “head separation” takes place. It can also crack and blow slap in half, and that’s what the “separation” part of case head seperation looks like.
Photo courtesy GS Arizona. This is a spot you should keep an eye on as your cases age. This is also the area that is “protected” best by using smaller sizes and less set-back. This is where the stretching movement occurs (the shoulder creates a gap). If you see a sign of a head separation, it could be due to a high load or excessive shoulder setback.
Editor: A bent paper clip can be used to detect potential problems with your case wall. To check for any thin spots, slide the paperclip inside your case. GS Arizona explains that this simple tool (the bent paper clip) can be used to check the inside of your cases before you reload them. As you run the clip along the inside of your case, the thin spot will immediately be apparent. If the clip is hitting a thin spot in the interior and you see a shiny line on its exterior, it’s time for the case to be retired. Photo by GS Arizona.Monitor Primer Pocket Dimensional Changes
The primer pocket is another case-head-area, pressure-related check. The primer pocket will become larger in diameter and less deep with each firing, as previously mentioned. As with many other such things, the questions are “when” as well as “how much,” but the most important is “how much.” Function issues could arise if the pocket becomes too shallow. This is determined by a primer that fits fully but isn’t at least a tick below the case base. A semi-auto with a floating firing pin can cause a “slam fire” and, if there’s actual protrusion, it can have the same effect as inadequate headspace. A primer pocket uniformer can adjust the depth of a shallowed prime pocket to the correct level, but what I really care about is how easily the next primer fits into it? If it has significantly less resistance, it is done. You can refurbish shallower. This is the primary function of a primer-pocket uniformer. However, it is impossible to fix a larger diameter. In another article, I mentioned that my main gauge for load pressure is how much primer pocket expansion has occurred.
Similar Posts:Tags: Cartridge Brass, Case Inspection, Case Separation, Case-Head, Glen Zediker, GS Arizona, Paper Clip Gauge, Rifle Brass
