Cartridge Case - What’s its purpose?

It has to hold the primer, powder, bullet and in most cases be easily extracted so the chamber is ready for subsequent rounds.

Cases have been made using plastics. Like these .223 they have crummy neck tension as you can pull the bullet by hand and often get mangled in semiautos but they can withstand the pressure, at least once.



Its pretty easy to understand that case strength is exceeded when fired because we all know they “blow out” and form themselves to the chamber walls. Why we resize them to reuse them. If your still not sure one can be set off outside of a firearm (do this safely) and the case will be destroyed because it had no support.

Functions of brass:

1) contain primer, powder, and bullet

2) SEAL the breach end of the chamber to ensure ejecta is propelled down the bore

Brass MUST yield to the internal pressure, and the chamber and bolt must sufficiently support the brass exterior to preclude structural rupture as it yields. Pretty simple stuff, but critical, and taken for granted.

Varminterror said:

2) SEAL the breach end of the chamber to ensure ejecta is propelled down the bore

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This is important. . . and add that in semi- or full-auto applications, ejecting the brass removes significant heat energy from the breach area that then doesn't need to be radiated to avoid cookoffs.

Edit: and don't forget the subsequent radiation of that heat energy into the epidermis of the guy to your right!

Extraction is really a side-effect of using a cartridge case, not a “feature.” Without a cartridge case, you wouldn’t need to extract it.

An example of a case that was not fired in any chamber sending the bullet down the barrel. So it just burst and the bullet sits there undamaged.



Then there are other instances of case failure. Like when someone creates a load with sufficient pressure to cause failure of the materials that are supposed to contain them. Then everything gives up.

The cartridge case protects the powder and primer from the atmosphere (variations in humidity, etc.)

From reloading/handloading .30-30, .30 Mauser, 6.5 Carcano and .308 Win, I have found consistent neck tension between case and bullet has a greater influence on consistent presssure, velocity, and accuracy than I realized.

There are features designed in to cases often to help with extraction, this is why many are made with tapers, so as the case move reward slightly, the friction to remove it is greatly reduced.

Some designs went the way of the dodo because they not only facilitated extraction but had problems locking up revolvers because the wanted to move reward upon firing. Like the .22 jet, center.



And some shapes would be right out.

Cartridge Case - What’s its purpose?
It,s so reloaders can reload.

Aside: When ammo burns off outside the chamber of a firearm, the primer pops, the bullet pops off, the powder burns and the case tries to fly like a miniature rocket.

obturate the chamber.

murf

All the info you need about cartridge components and more can be had from the book Metallic Cartridge Handloading.

No affiliation but highly recommended if you desire to become a master of the craft.

Isn't this a given that a cartridge case holds powder, a bullet and a primer and the case is manufactured to certain specs that enable it to fit chambers, also manufactured within certain specs to hold it! I fail to see the importance of the question as I could say, automobile, what's its purpose?

The removal of heat from the action of a firearm is another often overlooked function of the cartridge case.

I look at the primary purpose of a cartridge case being to eliminate the need for me to carry around a powder horn and a ramrod.

The case does provide a better seal than the chamber and bolt face.

This can be observed by examining a chamber that has been used with steel cases verses one used with brass cases. The steel chamber will show more fouling than the chamber used with brass cases, as steel does not deform to seal the chamber as effectively as brass.

Milt1 said:

Isn't this a given that a cartridge case holds powder, a bullet and a primer and the case is manufactured to certain specs that enable it to fit chambers, also manufactured within certain specs to hold it! I fail to see the importance of the question as I could say, automobile, what's its purpose?

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Why is it brass of certain dimensions, rather than other materials or other dimensions. The op discussed pressures and strength.

Varminterror said:

Functions of brass:

1) contain primer, powder, and bullet

2) SEAL the breach end of the chamber to ensure ejecta is propelled down the bore

Brass MUST yield to the internal pressure, and the chamber and bolt must sufficiently support the brass exterior to preclude structural rupture as it yields. Pretty simple stuff, but critical, and taken for granted.

Click to expand...

It must also retract enough for smooth extraction. The malleability of brass allows this better than steel. Aluminum wasn't a viable contender at the time brass became the standard metal for cases, and steel was still new enough that it wasn't considered until wartime conditions forced the issue.

Varminterror said:

Extraction is really a side-effect of using a cartridge case, not a “feature.” Without a cartridge case, you wouldn’t need to extract it.

Click to expand...

Caseless ammunition guns still have a means to extract unfired (whether unloading or a dud round) rounds. Until beam-type projectileless weapons are fielded, small arms will need some type of system to eject at least the projectile in case of misfire or to unload the weapon.

If you study weapons, you'll note not all of them have the cartridge case fully enclosed in the bolt/receiver junction. The 1911 is a prime example. Many rifles also have a 'gas port' built into the receiver in case of barrel obstruction or other reason the gas can't go forward. A caseless ammunition gun cannot have this, for obvious reasons. H&K solution was to build the gun so if it did happen, it would blow downward, where (hopefully) the shooter's body would not be.

Yes, heat extraction is a benefit, as is reloadability. Steel is reloadable, but it is hard on equipment. Aluminum is reloadable, but is incredibly fragile; I had quite a few Blazer (small primer ones are Boxer primed) case mouths crack when applying more than the smallest amount of flare. Getting more than one reload from them is iffy.

hardheart said:

Why is it brass of certain dimensions, rather than other materials or other dimensions. The op discussed pressures and strength.

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As mentioned, the correct combination of strength and malleability. I suspect other metals might be suitable also, for instance gold alloys, but for obvious reasons, not a really good choice.

Interesting thread. Most info I knew already but some really didn't..... And some I guess I knew but never stopped to ponder on

It also serves as a gasket. It seals the chamber and prevents gases from exiting the breech as the bullet seals the bore.