Every time you pull the trigger, lots of violent things happen inside the chamber of your gun.
The primer ignites.
The primer ignition sets flame to the propellant, which then begins to burn at an obscenely fast rate. It doesn’t technically explode (unless you’re using black powder) but it burns so fast you might think it’s exploding.
As the propellant burns, the chemical reaction creates high-pressure gas, which has to go somewhere—fast.
This swelling gas cloud inside your cartridge does two things. First, it expands the brass cartridge case until it’s pressing against the inside walls of the gun’s chamber. Then, it pushes the projectile hard enough to overcome the friction of the cartridge case mouth and launch it down the gun barrel.
As the bullet leaves the cartridge, and the pressure starts to drop, the brass cartridge case starts to shrink back closer to its original size—but not all the way.
The cartridge case mouth will be opened up a bit as a bullet that was comfortably seated there has just been violently ejected.
All of this happens in a split second and is the reason that, when reloading your own ammunition, you need to resize the brass cartridge case. While resizing the cartridge case rarely compresses a case to its original size, it will crush it back within cartridge dimension standards, allowing it to chamber in any gun of the proper caliber.
Resizing dies
A resizing die is simply a carefully-shaped hunk of metal that is used to “press” the empty cartridge case back to standardized dimensions. The brass cartridge case is forced into the interior of the die with a reloading press and the internal shape of the resizing die presses the brass back into the proper dimensions.
Think of this process as making a hamburger. You take a misshapen pile of ground beef, and using pressure from the outside, you shape it into the desired form. With fired brass, you take a cartridge case that has contained a massive conflagration, and therefore expanded in size, and press it back into shape. Unlike the hamburger, brass is hard and tastes lousy, hence the need for a steel reloading die and a reloading press to apply the the necessary pressure.
Brass is not as easy to “work” as hamburger meat, and significantly more pressure than is available with bare hands is required to reshape it to standard size. Squashing a brass case into a steel hole under great pressure will almost certainly result in a unified piece of useless steel-brass metal as two parts are hopelessly stuck. Why? Unlike hamburger meat, neither brass or steel have yummy, slippery fat grease naturally available. So, when resizing brass, you need to have some type of lubrication.
Depending on the type of cartridge you’re resizing, this can be done in a couple of different ways. Let’s talk about how that’s handled in both straight-walled and bottlenecked cartridges.
Pistol brass (straight-walled cartridges)
By “straight-walled” I simply mean that the cartridge case is shaped like a cylinder that has the same diameter from the rim of the cartridge to the mouth—like a toilet paper roll or aluminum soda can. Not all pistol cartridge cases are like this. A great example of an exception is the .357 Sig, which is shaped more like an old Coke bottle as it narrows as you get closer to the case mouth. In these rare cases, you need to resize it as you would a bottlenecked rifle cartridge. We’ll get to that in a minute.
Even though most pistol cartridges have straight walls and resizing is minimal, lubrication is still required. This is where ingenuity comes into play. Some clever reloading engineer figured out that carbide is a little more slick than standard steel. If you could make a reloading die out of carbide, then additional lubrication would not be required, as the brass case won’t stick to the carbide material. Most reloading dies for straight-walled cartridges have a carbide ring. As you pass the “ring” down the length of the cartridge case, it resizes as it goes—without grease.
Rifle brass (bottlenecked cartridges)
Case lubrication supplies, left to right: case lube pad, Hornady One Shot case lube, mica dry case mouth lubricant.
When your cartridge case is shaped more like a World War II pin-up model than a soda can, there are a lot more curves to press and shape into proper dimensions. In addition to the exterior sizing, bottleneck resizing dies also have a case mouth expander ball. This pushes inside the case mouth during the resizing step and opens the mouth just enough for insertion of a new bullet. This means there is even more opportunity for the brass case to get stuck in your reloading die. When you resize a piece of bottlenecked rifle cartridge brass, you definitely need to lubricate it first. One partial exception is case neck resizing. While outside the scope of this article, if you intend to use your cartridges in the same rifle, every time, you don’t need to resize the full case. But that discussion is for another time.
The problem is that you don’t want the interior or exterior of your brass casing to have wet and gooey lubricant after you’re finished resizing. If lubricant slop is left on the inside of your case, it can interfere with your powder or primer performance. If it’s left on the outside of the cartridge, chambering and ejection will be impacted. It can even be dangerous. If you use too much lubricant, you can dent your case when resizing. Remember high-school chemistry when you learned that liquids aren’t compressible? If you were sleeping or cutting class, here’s a hint: the brass bends first.
So when it comes to a case lubrication strategy, you have a couple of choices:
You can use a “wet” lube, like this RCBS Case lube pad. The idea is to apply a little RCBS lube to the sponge-like pad and roll your brass on it before resizing. You can also use a wet spray, like this RCBS Case Slick. These types of “wet” lubrication approaches work great. You have to work pretty hard to get a stuck case in your resizing die. The drawback is that you need to remove the lubricant from the case before firing. You can wipe each one off or re-clean the cases with a tumbler or ultrasonic cleaner after resizing.
If you won’t want to mess with the extra step of removing lubricant, you can try a “dry” lube approach. Products like Hornady’s One Shot are “waxy” in nature and don’t need to be removed. However, I’ve found them to be more sensitive to proper procedure. Generally, you need to spray on the lube, then let it dry thoroughly before resizing. If you don’t allow adequate drying time, you’ll get a stuck case.
The stuck-case scenario will happen to you, too. Just don’t mess it up like I did. Get yourself a stuck-case removal kit.
Tip: One small step that makes a huge difference is brushing and/or dry lubing the interior of the case neck. Simply brushing the gunk out of the case mouth prior to resizing reduces the resizing force significantly. If you want to be really smooth, dip the open mouth into some mica powder to provide dry lubrication to the inside of the mouth.
One thing is sure when it comes to rifle case resizing—you’ll learn by experimentation. You’ll get some cases stuck, which will require you to buy a stuck-case removal kit. Or, you can rig one up yourself from pieces and parts from the local hardware store. Either way, it’s money well spent.
With rifle cartridges, the payoff for perseverance with case resizing is great. Not only can you save a lot of money per cartridge, you can really tune a load to your specific gun for accuracy, power level, and intended use.
Tom is the primary author of the Insanely Practical Guides series of how-to books. He believes that shooting can be safe and fun, and works hard to make the shooting world easy to understand. If you want to learn about the world of guns, shooting and the American way, check out some of his books. Have a laugh or two. Life is too short for boring "how to" books.
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Feel free to visit Tom at his website, MyGunCulture.com. It's a half-cocked but right on target look at the world of shooting and all things related. If you want to learn with a laugh about guns, shooting products, personal defense, competition, industry news and the occasional Second Amendment issue, visit him there.
