Uh, naive urbanite ammo question

Factual Questions
1

All right, I admit it. I have no idea how a modern gun works. I’ve never touched a gun, or seen a gun, and I’m quite happy about being completely naive on the subject. I assume it’s still the basic idea of load a bullet, pull the trigger, and a hammer-type thingie, propelled by some small explosion, pushes the bullet out of the gun at an insane speed.

That being said, what is a casing, and how does it separate itself from the bullet? Why bother with a casing at all? Can casings be refilled?

Thanks in advance.

2

The casing holds the bullet and the gun powder and explosive cap. The hammer does not push the bullet. Instead it hits the cap, cause the cap to explode. This explosion ignites the powder in the shell casing, which propels the bullet forward. It is the force of the explosion that causes the bullet and shell casing to separate. Metal shells are used because they keep the bullet, the exact right amount of powder, and the cap all together in relatively safe storage, and ready for use. In the olden days you had to measure out the powder and place the cap manually before every shot. In the Napoleanic wars a good soldier could get off three shots per minute.

Some casings can be refilled. When I was a kid my friend’s Dad had a machine with which he could refill shot gun shells. It might have been able to refill rifle shells as well. Clearly full metal jackets cannot be refilled, the bullet destroys part of the shell.

I hope I got that right, or else Anthracite or someone else more knowledgeable than I will come by and correct me.

3

I’m no expert, but here’s what I know. What most call a “bullet” is actually a cartridge. A cartridge consists of a bullet, a powder charge and casing. A gun works thusly: a hammer strikes the bottom of the casing. In the casing is (I think) a primer charge, which is ignited due to the shock of the hammer striking it; the primer charge ignites the larger main charge of powder. As the powder burns, the gas produced expands, until the force is great enough to propel the bullet out of the casing. Therefore, the casing’s role is to package everything together, and allow the exploding gases to build up to pressure. In early guns, there was no such thing as a cartridge, so it was all kind of poured down the barrel (powder charge, wadding, bullet, primer powder, etc).

4

Boy that looks stupid. I post directly beneath what I’m responding to, but I still felt the need to quote his/her entire post. Oh well, what the hell.

5

Modern semi-autos are really cool, BTW. Once the bullet is ejected from the gun, the barrel assembly slides back (due to conservation of momentum) at which point a mechanisms pops the emtpy casing out the side, and makes way for the next cartridge to pop into the barrel.

6

Good response, but I have to nitpick here. There is nothing to stop one from reloading a round that was originally FMJ. Since some people may not know, a “full metal jacket” or “FMJ” bullet is a bullet that has a (usually copper or some alloy, I think) “shell” over its entire lead core. (And by “bullet”, I’m talking about the projectile; not the whole cartridge.) “SP” os “softpoint” bullets have the metal jacket that does not extend all the way to the point. That is, there is exposed lead at the tip. “HP” or “hollowpoint” may or may not be jacketed.

Here’s how reloading works: The case is cleaned using a polishing medium in a machine that vibrates a bowl that contains the medium and the cases. The cases are then lubricated and passed through a sizing die, which also punches out the primer (the explosive cap). A new primer is installed and powder is measured into the case. Put a bullet on top of the case and run the cartidge-to-be through the seating die. Viola! You have a new cartridge! Of course if you only have one reloading press (not a progressive reloader) you’d want to do many cases at each step, rather than make one complete round at a time.

It doesn’t matter what kind of bullet you put in the case (FMJ, SP, HP, etc.), but there are things to look out for. If the case has been reloaded a few times, all of the expanding (from the pressure generated during firing) and contracting (from the sizing die in the reloading process) will fatigue the metal. If there is any evidence of a crack, the case should be discarded. Some people crimp the necks of their rounds (many bullet choices have a “band” around them to allow for crimping). If a case has been crimped a few times the neck will become fatigued. If any metal has “flaked off” the rim of the neck, the case should be discarded.

7

The barrel assembly slides back in some weapons in the manner you describe. In other cases, such as most assault rifles, the bolt or breech block (the assembly that holds the firing pin) is propelled backwards by gases from the explosion of the gunpowder that are transferred back through a gas tube. In still other cases, the mechanism is simpler and simply causes the bolt to be blown back by the gases in the barrel, as is the case with the old Sten gun.

8

Technically, an “assault rifle” is a rifle that can work automatically (like a machine gun) as well as semi-automatically (one shot per pull of the trigger). Machine guns are illegal in most states and require an extensive background investigation (similar to getting a Secret clearance) and payment of a Federal “transfer tax”. Even though Federal law allows ownership of machine guns, you still have to live in a state that allows them.

There are two types of semi-automatic (and automatic) actions. One is the “recoil operated” (AKA “blowback”) action in which the force of the rapidly-burning powder (gunpowder burns rapidly, rather than explodes. A fine distinction, but there you are.) overcomes the mass and inertia of the bolt. The action is designed to not push back the bolt until the bullet is safely on its way down the barrel.

The second type is the “gas operated” action. Gasses that propell the bullet are taken from a port somewhere in the barrel. Most people know what an M-16 looks like from seeing them in the movies. The triangular piece near the muzzle (the front of the barrel) holds the front sight and is also the place where the gasses are ported from the barrel. There is a tube that runs from the front sight (in the M-16/AR-15) back to the bolt carrier. The gasses travel down the tube and act against the bolt carrier to push it back, cocking the hammer. A spring (in the M-16/AR-15 it is in the butstock) returns the bolt carrier assembly to the closed position, chambering a new round along the way. Some gas operated systems (as in the AR-18/Ar-180) use a piston. The gasses push a piston that pushes a rod that pushes the bolt carrier.

Although RickJay didn’t imply it, I’ll say it anyway: All “semi-automatic rifles” are not “assault rifles” (especially considering the technical description). There are semi-automatic actions in pistols, hunting rifles, shotguns, and even your little .22 “plinker”. This is one reason “gun nuts” oppose regulation of “semi-automatics”. (There are other reasons, but you can read all about them in GD.) An AR-15 so-called “assalt rifle” and a Ruger Mini-14 ranch/hunting/sporting rifle are functionally the same. They both fire the same round, they’re both gas-operated, and they’re both fed from detachable magazines. The difference is that one os black and the other comes with a wooden stock.

Semi-automatic pistols may have a sliding bolt (like the Luger P.08 or the Ruger MkII) or the whole top of the gun may move back (the “slide”, as in the Colt 1911 or the Beretta). Revolvers have a cylinder that holds the rounds. These are the “six-shooters” of the Old West, and the .38s you hear about in the old cop shows. There are also bolt-action pistols that are used for target shooting and hunting.

Bolt-action means that there is a bolt that must be manually operated. If you saw Saving Private Ryan, the sniper used a bolt-action M1903 rifle. The German Gewehr 98s in the movie were also bolt-action. Bolt-action rifles are very popular with hunters, and have also been used on some shotguns.

Lever-action rifles have a lever below them. Think of The Rifleman series or any of the old westerns. Manipluating the lever opened the action, ejected the spent case, cocked the hammer and chambered a new round. Interestingly, one of the first “machine guns” was made from a lever-action rifle. A “technology demonstrator”, it had a flap over the muzzle that was attached by a rod to the action. When the round was fired the gasses would move the lever out of the way of the bullet and work the action at the same time.

Pump-action firearms have a slider under the barrel. These are popular on shotguns (“Rack-rack!!!”) and have also shown up on hunting rifles and “arcade guns” (.22 rifles used in shooting galleries).

Break-actions are usually on shotguns. There is a pivot on the receiver that allow the gun to be “broken”. The shells are ejected or manually extracted and new rounds are inserted. Closing the action cocks the gun and makes it ready to fire. There have also been break-action pistols and rifles.

Falling-blocks were used in early cartridge guns, for example the Sharps 1873 and the earlier Sharps non-cartridge breechloader, and the Martini rifles featured in Zulu. A lever dropped the breechblock and allowed a round to be inserted or a spent case to be extracted. Most had a hammer that needed to be cocked as well.

Single-action and double-action are subtypes. A single-action firearm requires that the hammer be cocked manually for each shot. A double-action cocks the hammer when the trigger is pulled. A single-action automatic requires the hammer to be cocked manually (either with the thumb or when the slide is operated) for the first round. The hammer is cocked automatically for subsequent rounds. A double-action automatic cocks the hammer when the trigger is pulled for the first round, but the hammer is cocked automatically for the rest of the shots. Revolvers operate in the same way, except that the hammer is not cocked automatically. Most double-action revolvers can also be used single-action. Since it takes such a hard trigger pull to cock the hammer on a double-action revolver, accuracy may suffer.

A “hair trigger” is a trigger assembly that has been modified to release the hammer at the slightest touch of the trigger. This is useful for competition shooting, but is dangerous on a firearm that is to be carried. Some older rifles had two triggers. One would release most of the pressure on the trigger assembly and the other would be used to fire the round. The latter would require a much lighter pull than would be required if the first trigger was not pulled.

9

Hey Johnny - you forgot to explain the difference between “open” and “closed” breech.

10

Allow me. :slight_smile:

When an open-bolt rifle is cocked and ready to fire, there is no round in the chamber. The trigger pull releases the bolt, which takes up a cartridge from the magazine. Once the round is chambered, the hammer is released, firing the cartridge. The bolt is operated (either by blowback or gas discharge), locking once again in the “open” position, ready to chamber and discharge another round.

In a closed-bolt rifle, when the weapon is cocked, a round is in the chamber and the bolt is, well, closed. The trigger pull releases only the hammer, firing the round, the bolt is operated, a new cartridge is loaded, and the hammer is cocked.

Open bolt weapons are much more practical for fully automatic fire, which is why nearly all civilian weapons in the US are required to fire from a closed bolt.

Incidentally, the only difference between a semi-auto, full-auto, and plain old bolt-action rifle is how the bolt is operated. In a bolt-action, you operate it by hand. In a semi- or full-auto rifle, the bolt is operated automatically (hence the name) for you by various means.

Anything I missed?

11

Also must commend Johnny on the proper definition of an explosion. IIRC, all explosions are burns, ie., the rate at which a material burns determines destructive force, sound, etc.

12
      • Ooooh! Oooooh! - You forgot modern caseless ammunition/guns. Solid propellant, electric ignition, no case. Only one example I know of made by Steyer: a civilian hunting rifle, but it is the future. -They wanted like $2500 for the bolt-action gun and $8 a shot a year or so ago, for what was weak .243 ballistics. -Ouch!- ~~~ IIRC a German police submachinegun was developed for it but I dunno if they’re using it there or not.
        ---- Interestingly enough, there’s a rather vicious debate in the anti-gun AND gun community about if caseless ammo is a good thing or not. It’s kind of a red-headed stepchild of the gun control debate; most higher-up people on both sides prefer not to bring it up at all. The arguments go like this:
  • People (this includes various law enforcement agencies) point out that caseless ammo doesn’t leave one piece of often crucial evidence at the scene of crimes: it has no case.
  • BUT---- Caseless ammunition is damned impossible for regular folks to manufacture in their garages or kitchens, while the regular stuff they have now can fairly easily be reloaded and reused. The thinking here is that if all guns go to caseless ammo and the gov’t decides at some future date to ban ammo sales, there’s no effective way for people to make their own ammunition.
    —SO—nobody really knows if they support its use or not. It costs too much now for most gun enthusiasts to bother with anyway. Eventually the military will adopt it though, and the price will get much much lower. - MC
13

A casing of course!

lets get some basic terms straight.

Bullet - projectile
Cartridge - assembled round of live ammunition
Casing - metallic (usually) container which holds bullet, primer and propellant
primer - cup-shaped metallic (usually) container used to hold an impact and pressure sensitive primary explosive such as lead azide, melcury fulminate (in the old days) or perchlorate compositions.
detonator - an explosive device to initiate tertiary explosives and having no practical use in smallarms and cartridges

The hammer usually is tripped by a sear on the trigger mechanism and under spring tension strikes a firing pin (in some weapons) or has an intergral pin.
The pin strikes the primer, and causes an amount of priming compound to be under high pressure between the deformation of the primer (indentation caused by the pin) and the anvil ( a small metal spiderlike thang in boxer-style primers or a pimple-like protrusion into the primer pocket in the case of berdan primed cases).
On swift compression the priming compound detonates and causes a large flame front to propagate through the primer hole into the cavity of the casing body where it rapidly ignites the propellant charge.

These days propellant is usually a double base nitrocellulose granulated powder as opposed to the hydroscopic, temperamental and corrosive black-powder (aka gunpowder). There are slow burning powders for rifles, fast burning powders for shotguns, and medium burning powders for handguns. There are modern versions of black-powder which are more stable and less corrosive.

The rapid but controlled deflagration of the propellant produces an enormous pressure (measured in Copper Units or Lead units of pressure) causing the casing to expand and seal the breach of the gun, and forces the bullet down the freebore, and into the rifling of the barrel which induced a rotation of the bullet (to average out errors in aerodynamic or centre of mass of the bullet).
Tne bullet exits post haste, the gasses expand out of the barrel and unburnt powder flies out like demonic pin-flies.

some points to note:

  1. primers are wickedly explosive and should be treated with great respect.
  2. “blanks” or bulletless cartridges are capable of immense damage at short range and firing a blank in yer ugly mouth will blow your head to pieces - probably more so than the bullet would have.
  3. computers are unparralleld for their ability to allow a single human to cause huge amounts of damage, except for alchohol combined with a firearm.
    zat enuff?

for more info try:
Hornady
RCBS
Lyman
Olin
Nobel

14

** Johnny L.A.** said

Not that I want to argue the point, but one of the problems with gun control legislation is they don’t define the terms. Could you tell me where that definition came from? It would exempt my SK-47 even though it has a “permanently attached” bayonet. :slight_smile: :slight_smile:

15

They’ve been working on caseless ammo weapons for years now, and IIRC there are two basic problems with them:

  1. They’re messier, so they’re less reliable.
  2. They heat up faster (I don’t know exactly why.)

Modern military assault weapons are probably not going to be replaced for quite some time. The M-16 is a phenomenally efficient, cheap, and effective weapon. You’d be hard pressed to create a weapon that was substantially superior in performance, reliability, and ease of use and not bust the federal budget doing it.

16

hardhead365, I don’t have the cite as I’m at work right now, and in any case all of my reference books are packed away for my relocation (any time now! :rolleyes: ); but “assault rifle” has meant a selective-fire weapon since its inception with the Sturmgewehr-42 (literally, “assault rifle”, model of 1942). The term stuck until firearms such as the AR-15 were made available to the public. Since the M-16 is a true “assault rifle”, and since the AR-15 is a semi-automatic version of the M-16 (actually, I believe the name AR-15 came first) the AR-15 was commonly but erroneously referred to as an “assalut rifle”. In the 1980s there was a call to ban these evil things, enven though as I said before they are functionally identical to sporting arms. “Assault rifle” seemed a nice phrase that sounded good in sound-bytes. I can’t be certain, but I think the term currently in use is “assault weapon”. Whether this is a result of people asserting that assalut rifles are by definition selective-fire, and calling the arms in question “assault weapons” might sidestep a legal technicality; or it is an attempt to lump many kinds of weapons together under one umbrella term, I don’t know.

The deal with your SK-47 is this: You may not have heard of them, but there was a rash of bayonette attacks in the 1980s. Really. Bayonettes were used so often that they had to be banned. Okay, I’m kidding. I think the rationale behind banning firearms with permanently-attached bayonettes or with bayonette lugs is that they are “military” in nature and thus people should not own them. (Hmmm… Maybe I should turn in my flight jackets? They’re military in nature too!)

I think what it comes down to is this: It’s impossible to distinguish between martial and civilian firearms by reference to their operating systems. “Semi-automatic” covers a lot of guns, a good number of which (in the U.S. I’d venture to say the majority) are definately civilian. So the lawmakers have to come up with some way of telling guns apart. “This one is black, so it’s bad. This one has wood on it, so it’s not bad.” That sort of thing.

When it comes to gun control, once a law is passed, it’s passed. It’s very hard to get it repealed. And when out professional politicians want to get re-elected, they pass more laws. When those laws don’t work, they pass more laws (which don’t work). Yikes! I’m getting dangerously close to a Great Debate here! Back to the question…

The reason your SK-47 is banned is because it posesses a feature that was defined, perhaps arbitrarily, as a feature of an “assault weapon”. As such, your SK-47 will need to be registered, moved out of state, or turned in (without compensation) to the authorities.

17

Daisy, the BB gun manufacturer, made a single shot rifle [.22 VL] in the late 1960’s that used caseless ammo. It worked like a BB gun, in that you cocked a lever to pull back a piston and compress a spring. Pulling the trigger released the piston, compressing the air. The heat from the compressed air ignited the caseless ammo.

I have one and the ammo still works fine.

18

Oh, I do knoe how to spell “even” and “definitely”! :wink:

RickJay is right. The M-16 is a truly great firearm. There were problems with the first ones to see service (the barrel was not chrome-lined and was susceptible to corosion, for example), but the latest ones are quite formidable. Tolerances are pretty tight, so it takes a trained shooter to know how to take care of the rifle in the field. By comparison, the AK-47/AKM and variants are very “loose”. They’re made to be used by untrained or barely-trained shooters. The AKM is elegant in its simplicity. The M-16A2 (or whatever the latest model is) is elegant in its sophistication.

19

I give up. :rolleyes:

20

One of the really nice points about the AK line was not so much that they require little training to shoot, but that they would continue to shoot for untrained operators, even in harsh conditions. I think it was the history channel that did a nice interview with Mr. Kalishnikov, in which he said he’d designed it with enough “play” that you could open the bolt, toss in a handful of sand, rack the bolt open and shut once then load up and fire. The M16 variants don’t care for that kind of treatment. The originals were unpopular for reliability issues that have been blamed on everything from their unlined bore, to messy powders used in the original issue military ammo, but the big culprit really seems to be that the guns were rushed into service without thorough training in cleaning & maintenance.

As for the evil “black” rifles… Guess I’ll have to hide my Mini-14 since I went for the composite stock, eh? :smiley: