Some questions about guns

I know nothing about guns, so:

  1. Cocking a gun: what is the purpose? Presumably the gun can be fired without cocking. So is the cocking to save, what 50 milliseconds in firing time?

  2. Automatic and semi-automatic guns. What’s the difference? And are there guns that are neither? Are they called manual guns?

  3. Why do people saw off shot guns? Is it solely to make them more compact (fit in a bag or violin case?) or is there another reason?

  4. Every damned forensic show I watch has shell casings as evidence, and the forensic results are usually conclusive. Why in the hell aren’t the criminals picking up the bloody shell casings after the crime? “Hey, I’ll shoot you 4 times and just leave all this evidence behind!” Is it not understood that casings can be traced to a specific gun?

  5. Presumably rifles are more accurate than hand guns, due to the barrel length. So, if that’s the case, why don’t we see sniper guns with like 10 foot barrels? Perhaps there’s a tradeoff between barrel length and bullet velocity?

  6. Is there an expiry date on ammunition? Do they lose efficacy over time, or are they good forever?

  7. Is lead the prime composition for bullets still, or are steel bullets (or other compositions) taking over due to toxicity concerns…

Thanks.

Others may provide more in depth answers, but here we go-

1- You need some sort off force to hit the firing pin that hits the primer that fires the shell. There are a number of different configurations for this. When you see a handgun fired without cocking it, the squeeze of the trigger cocks the gun. This takes more force from the shooter, and the trigger travels a longer distance. This extra effort on the shooters part will (for most folks) reduce your ability to be accurate.

For a semi-auto, cocking it also loads the first round in the barrel. Subsequent rounds are loaded ‘automatically’ using the force of the last round fired.

2- The line gets blurred here a little bit because people don’t use the right terms. An automatic may be a semi-auto, or a full auto. A semi-auto shoots one bullet with each pull of the trigger. A full auto continues to fire when the trigger is depressed. Think ‘machine gun’.

3- I would think concealment mostly. However, the shot from a sawed off shotgun will spread into a wider pattern at less distance. Depends on the goal of the shooter. If the target is farther away, this cuts down on the lethality.

4- Criminals are dumb, and in a hurry. And in an uncontrolled situation, the shells can be hard to find. And it doesn’t help if the authorities don’t have a gun to trace it to.

5- Diminishing returns. Also makes the gun unwieldy.

6- For all practical purposes, ammunition lasts forever.

7- Lead is the primary material. It’s heavy and malleable making it effective as a projectile. I know some places require steel shot for shotguns/bird hunting due to environmental concerns.

it depends. a “single action” firearm means the trigger has one function, which is to release the hammer in order to fire. old-style revolvers (think “cowboys”) are single-action only, which means you have to manually cock the hammer. Also, most long guns (shotguns and rifles) are single action, but the hammer is cocked by cycling the action.

many revolvers and pistols are “double action,” which means the trigger can do two things: 1) draw the hammer back, and 2) release it. some can still be fired single-action, others are double action only.

then there’s striker-fired guns like Glock pistols, which are somewhere in the middle.

a full automatic weapon will continue to cycle and fire as long as the trigger is held. A “semi-automatic” is more correctly called “auto-loading,” since it only fires once per trigger pull but cycles and chambers the next round. non-auto-loading guns are referred to by the type of action, e.g. pump-action, bolt-action, break open, etc.

yes. note that doing so is illegal in the U.S.; the minimum barrel length for a long gun is 16".

except they can’t be unless you also have the gun, and even then it’s hard to conclusively prove a particular gun fired a particular round.

The best thing to remember is that everything Hollywood says about guns is wrong.

yes. once the gunpowder is finished burning, you want the bullet to exit the barrel. otherwise it’ll slow down due to friction in the bore.

lead is still prevalent, but for the most part they’re a lead core with a copper jacket. Copper is still malleable enough to take the rifling but leaves a lot less fouling behind. And un-jacketed lead bullets are a no-no in barrels with polygonal rifling.

To add to what jz said, with Double Action firearms, manually cocking the firearm usually results in a lighter “trigger pull” to discharge it, which may also enhance accuracy.

Note that at the Federal level, fully-automatic firearms are legal for civilians to own, but still heavily restricted. A 1986 law “froze” the Federal automatic firearms registry, restricting it to only the guns currently in circulation at that time; no new-manufactured guns can be added.

In the classic “supply-and-demand” fashion, this has driven the price of fully automatic firearms through the roof.

Also note that while legal at the Federal level, several states have banned civilian ownership of fully-automatic firearms.

Lead bullets deform, often badly, upon impact, and the forensic trope of matching bullets to a specific gun that ostensibly fired it is often simply impossible.

Essentially correct; the barrel needs to be long enough to impart enough spin to stabilize the bullet while there is still a force “pushing” it down the barrel; if the burnt-powder-gasses dissipate too much, for whatever reason (barrel length, or other “escape” routes"), the bullet will begin to lose velocity while still in the barrel, due to the bullet’s friction with the barrel.
It’s fairly rare, but occasionally you hear of “squibs.” A squib is where the hammer/striker ignites the primer, but for some reason the powder doesn’t ignite (if it’s even present!).

The primer has enough force to separate the bullet from its casing and lodge it in the barrel.

The next shot might be fairly spectacular (think Elmer Fudd’s exploding barrel), and potentially very, very nasty for the shooter.

Makes me ask: Did the machine guns on a WWII fighter top of tanks, etc., ever had a squib and blown up the weapon /damaged the wing? I never heard/read anything about that.

Also, on the Gatling guns the shells are mechanically removed, correct? Weapon does not care if each one fires or not?

Sawed off shotguns are more concealable. And the shot spreads more over a short range. And they’re illegal in the US. The minimum legal length for a barrel is 18" and the minimum overall legal length is 28".

jz? No.

The 16" thing has to do with pistols, sub-machine guns, and carbines. They generally all fire the same cartridge. Different rules apply to sub-machine guns. But other rules come into play when a manufacturer introduces a civilian (semi-auto only) version of a sub-machine gun.

It’s illegal in the U.S. to have a fixed or folding stock on a pistol. You can have either or no stock on a carbine. What makes a carbine? A minimum 16" barrel. So the civilian versions of the Thompson or the Uzi have 16.5" barrels.

Shells are ejected fast and can travel some distance. If you’re shooting you’re probably concentrating on aiming and not where the shells are going.

There’s a lot of ammunition dating back to the 1950s that people are still shooting (ealier than that it’s generally more valuable as collectibles. You might have an occasional dud is the only problem.

There’s also a minimum overall length for a rifle or carbine. I think there is an exception for stocks on pistols. I think that the holster/stock may be affixed to the ‘Broomhandle’ Mauser C96, but it’s been years since I read about it. (I think it must be an original stock, and not a reproduction. Something like that.) Also, I believe that stocks may be added to cap-and-ball pistols, which are not strictly ‘firearms’ under federal definitions.

Yes. It’s fired by an electric motor and each barrel has its own firing pin and bolt assembly. Basically it’s six spinning machine guns.

I may break this into chunks.

  1. I will assume you are talking guns with exposed hammers like the usual revolver. Single-action guns cannot be fired unless you cock the hammer; double-action guns can be fire either way. Cocking does not save time, it costs time - but it does allow for a more accurate shot as you have less impact (use less force and take less time) on the trigger.

  2. Technically an automatic will fire three or more bullets on a single pull of the trigger, a semi requires a pull of the trigger for each shot you want to fire. But from early on the terms have had a sort of interchangeability since most semi-automatics are capable of automatic fire with some modifications.

Lots of guns are neither. Pump, lever, single shot (although some auto ejects could basically be a semi frame), bolt actions. And that is without throwing in odd stuff like falling blocks and more. Usually (not always) action is defined as as the parts that load, fire and eject the spent casing; the name of the action usually describes how that happens.

  1. Size is usually the main reason but its also to remove the choke/constriction built into most shotguns to make them shoot tighter. In other words, to keep the shot in the smallest area possible at different ranges. If you are cleaning out a room of people this constriction is a bad thing - you want the shot to spread as fast as possible so you hit as many people as possible. Or hit the one person no matter how bad your aim is. Cutting behind the choke and making the barrel helps accomplish this.

There are two other modifications for more combat effectiveness in a shotgun. One is what is called a riot trigger for a pump action. This allows you to hold the trigger back and fire as quickly as you can work the pump. The other is for the old-style side-by-sides and is called a dead-man’s trigger. Basically you wrap wire around the triggers and the trigger guard holding them into the “fire” position. That way all you need to do to shoot is thumb the hammer back and slip your thumb off. You can also hold the hammer back holding whoever “hostage”. If they, or anyone, makes a move against you your thumb comes off and boom.

  1. because criminals are often dumb or clumsy in the heat of the moment and TV shows aren’t quite reality. Usually one of the real-life signs of a professional shooting (or the act of a more intelligent and dedicated amateur) is the lack of evidence left behind.

Legally, an automatic will fire more than one round per pull of the trigger. I’m not aware of any firearm intended to fire only two rounds through a barrel with a single pull of the trigger. You are correct that there are automatic rifles designed to fire three rounds. Two rounds is a malfunction (but can be used to prosecute).

They certainly exist, whether you are aware of them or not. Both the AN-94 and the MP5 Navy have two-round burst mode as standard.

  1. At one time snipers did use barrel lengths as long as 10 feet (this is in the flintlock days) but they found out something - at a certain point length doesn’t help. With the modern faster-burning powders this is especially true. And the differences on different lengths isn’t as great as you would think. Vise-fire a 6 inch barrel and a 24 inch barrel with the same cartrige and the group sizes are going to be pretty darn close to each other.

Where length of the barrel helps more is sighting accuracy. On a short barrel you can be way off in site alignment and never notice. Move that out a foot and all of a sudden any small distance you are off becomes glaringly obvious. That is why so many handguns for hunting have scopes and other devices; with those you take the sight differences out of the equation and all of a sudden your 6 inch pistol can cut groups the same as a rifle.

Try this experiment: take both hands with your pointer finger out and up. Hold them up in front of your face in line so they block something at a distance across the room - for sake of argument lets say your left is closer to your face (say 8 inches away from your nose) and the right is say 4 inches further away. Move the front/right one slightly side to side and look at how far you can move it before your target is revealed. Now take the right one and move it as far away as you can and still keep it in line. See how much less you can move it side to side before the target is revealed? That is why a linger sighting plain is an advantage.

Now there is a point of diminishing returns on this. The human eye can only focus on one thing at a time. What we are usually taught is to focus so that the front site is crisp and the rear site and target slightly blurry. Get the front sight too far from the rear sight and either it or the target will get really blurry and throw off your accuracy.

  1. In theory, if properly stored a shell will be good for hundreds of years. I’ve personally shot rounds that dated to the 1870s/80s. However after x number of years (the x being variable from many factors) the rounds will be slightly less accurate. That is why “match ammo” (rounds loaded to the strictest standards for the best accuracy possible) is dated. And why military and police snipers will often return older rounds and draw a “fresh” supply. For most of us the difference between a brand-new match shell and one two years old would mean nothing - we aren’t trying to hit a head shot at 1000 yards. But for those who are --------

One place where old shells can be a drawback is reloading. Older brass tends to crack and split more often than newer brass. We’re talking identical metals produced by the same company from the same machines but years apart. I got a great deal on my favorite Remington .30-40 Krag round; factory loads but vintage say 1960-70. Only about half made it to one reloading and fewer still to five; the rest all split somewhere around the neck.

  1. Pure lead fell out of favor like 100 years ago or more. Most are alloys containing tin, lead and other compounds. And most are at least partly copper jacketed. But you have all kinds of funky stuff out there now right up to radioactive materials.

Other than for shot for waterfowl, steel shot being required there, toxicity really isn’t the concern. Lethality is the concern. And in general terms, for most of us, nothing kills better than the basic hollowpoint semi-jacketed lead alloy bullet.

Some people might saw off shotguns to get a greater spread, but if that’s the reason they’re doing it, they’re misguided. A shotgun, even a sawed-off one, has a very small spread at any relevant range. The spread of the pellets will almost always be much less than the size of your target, which means that it does very little for making aiming easier, or for hitting multiple targets at once.

A good place I can recommend for really basic learning is the state hunter education programs. If you want to PM an address I could send you a student manual. It has a ton of basic learning on action types, ammo and lots of other stuff. It may be online somewhere but the only place I found in a fast Google wanted a fee for downloading the “e-book”.

Actually, “double-taps” as I was taught to call them, were legal at one point although that very well could have changed and few makers were designed them that way. A couple did but not very many and most of those were reserved to military and law enforcement.

The ones (two to be exact) that I shot had modified sears so that if you pulled the trigger normally you popped one round. Do it just right, just a little slower, and the gun fired, caught a second point on the sear and then released from that and fired again. One pull, two shots. The argument was (and I never got into it not really wanting to own one) that it way a way around the extra tax and all.

Some things just bear repeating.:smiley:

The Army replaced the standard 5.56mm round with one that has no lead in the last couple years. It was developed with the intent to be a training only round (so they didn’t have environmental cleanup costs at heavily used ranges.) They managed to improve performance as part of the same program so it became an operational round as well. Last I knew they were working on a similar round in 7.62mm. There was a price difference, though, even though it was small. That cost difference of implementing like that for recreational use is probably a bigger deal.

[Quote=GusNSpot]
Makes me ask: Did the machine guns on a WWII fighter top of tanks, etc., ever had a squib and blown up the weapon /damaged the wing? I never heard/read anything about that.
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Based solely on my own experience a round that completely fails to fire, while rare, is far more common than a squib. That can just be removed by cycling the action. I never saw/heard of a squib actually happen. You likely wouldn’t hear about the rare occurrences in the military anyway. Ever hear a story about the venerable “Ma Deuce” exploding because someone failed to properly adjust headspace and timing after swapping the barrell? It’s a different cause for the boom, but it happens.

Once you get behind the choke (remove it) I would tend to agree with you; a 24 inch “modified choke” barrel cut to 18 inches is going to be about the same at 20 feet as one cut to 6 inches. But the difference between “cylinder bore” (no choke at all) and say a Modified or Full choke at 20 feet is, IMHO, enough to make it worthwhile. Especially using buckshot.

(Its one of the reasons say #6 or smaller is being recommended more for home defense - tighter shot area and less shoot-through.)

Besides — it just looks mean as heck pulling out a double that’s only 8 inches long! :smiley:

  1. Even gas operated semi-autos, like most of the handguns you see on TV or in movies, require an initial cocking to set the tension on the spring that releases the firing pin, and of course to load the first bullet. After the first shot is fired the force of the expelled gas from the first shot ejects the empty shell casing, re-sets the tension on the firing spring and loads the next round. Just pull trigger again to fire until empty.

This is why it looks particularly stupid when you see a person in the movies pointing a gun at the bad guy, making his pointless speech, and then pulling the slide back on his handgun like he really means business now. If the slide has not already been pulled back to set the spring tension and load a round he might as well be pointing his shoe at the bad guy. The gun cannot fire if there is no tension to propel the firing pin. But you see this movie action all the time.

Actually I believe its 16" for a rifle and 18" for a shotgun although most makers add an extra half inch in case you have to recrown the barrel. And its not totally illegal - it just takes extra paperwork, taxes and stuff.

There are also legal “sorta-loopholes” around that paperwork and tax too. For example, there are firearms out there that are basically pistol versions of the M1 carbine. Now they have to be registered as, and are legally considered, pistols and not rifles ------ but in the end the difference is as much look as anything else. Look into the Universal Enforcer for example.

Trust me ---- anything firearms related gets real complicated and real “usually” very fast.

Second part first – it can matter. Some manual models of the Gatling have a shorter extraction port than loading port so a totally unfired round could jam up the works. I don’t believe that is the case with the modern “mini-gun” versions.

First part; what I think you are talking about is a shell loaded with a primer and no powder. In theory the primer goes off, pushes the bullet into the barrel, and if you shoot again the gun blows up since the first bullet acts as an obstruction. Because of how ammo is manufactured, the chances of that happening (no powder at all) is incredibly tiny. If there is going to be a failure its usually at the primer which means the shell is a total misfire. It WILL happen sometimes in handloads/home reloads but even there it is really rare.

But lets look at the worse case - no powder or so little powder that the bullet gets stuck. This would mean the gun wouldn’t have enough recoil to load the next round since the action needs either gas or recoil to operate. Anything/any round generating enough of either to load the next round would generate enough power to clear the bullet from the barrel. Follow me? So that round has to be cleared manually and the next shell brought into place and fired without the gunner knowing he had a blocked barrel.

Could it have happened to some machine-gunner sometimes during WW II? Maybe. Heck, some time somewhere or other some soldier could have been struck by lightning. I never like to say never. But for it to happen on a plane and remove the wing, the pilot would have to walk out on the wing and clear the jam first. There I may break my rule and say “never happened”.

The laws change so often I just avoid most of the fine points. If you don’t you also get into what can be legally owned by you and me as opposed to a federally licensed collector and what guns are considered curious this year and what the exact exception list is and all kinds of other stuff. All subject to change without notice.