"machine" gun versus "submachine" gun

Depending on who’s talking/writing, a fully automatic firearm (i.e. hold the trigger continuously to fire repeatedly) may be referred to as a “machine” gun or as a “submachine” gun. Is there a distinction between the two? If not, why do both terms exist?

“machine gun” typically refers to weapons firing a rifle caliber or larger. “submachine guns” typically refer to weapons firing a pistol round (e.g. H&K MP5.)

A submachine gun uses handgun rounds. A machinegun uses rifle rounds. Sometimes “machinegun” is used to refer to any burst or automatic weapon.

Submachine guns are smaller, lighter, usually have a range of 50 to 200m. Machineguns are more diverse in size/weight/range but they’re usually at least a dozen pounds and have a range of at least 1km.


Submachine guns:

A machine gun fires rifle rounds, a submachine gun fires pistol rounds. The classic submachine gun is a Thompson (Tommie gun), which shoots .45 ACP. A true machine gun is a crew served weapon, typically using belt fed ammunition, but not always.

FWIW, a lot of guns are called machine guns when they are not: M-16, AR-15, Tec-9, etc. Those are automatic or semiautomatic weapons

OK, next question: what’s the difference(s) between a handgun round and a rifle round? I’ve shot .22 rifles and .22 handguns that appeared to use the same ammo (though it was years ago, so not certain).

More of a rule-of-thumb than anything else: pistol rounds have a straight sided casing, where rifle rounds are necked. You can find exceptions both ways.

Do rifle rounds generally have more propellant?

There’s also velocity. Handgun rounds are seldom faster than ~ 1300 fps while most centerfire rifle rounds run 2500- 3000.

To add a little to what VunderBob said, here is a photo of some rifle cartridges, and here is a picture of some pistol cartridges. Generally, pistol cartridges are straight and shorter than rifle cartridges of a similar caliber.

Yes, quite a lot more.
Keeping in mind that we are speaking in terms of what is typical, handgun rounds emphasize portability over performance, rifle rounds the opposite.

Handguns rounds seldom go below 850ft/s or above 1500ft/s. Rifle rounds usually hang around 2300-3100ft/s.

A 9mm NATO round will typically have .3 grams of propellant with a bullet that weighs about 7.5grams. A 7.62 NATO will have 3 grams of propellant with a bullet that weighs 10 grams.

Even a 5.56 NATO with its 3.5 gram bullet has more propellants (about 1.5grams) than a 9mm NATO.
A handgun is like a dagger. A rifle is like a sword.

So pistol = usually bigger, slower round…and rifle = usually smaller but faster round?

Wow. To my newly educated eyes, that seems like a big difference in the amount of propellant. Thanks!

Yes, energy requirements go up at the square of the velocity you want.

But then, the weight of the propellant which turns into gas itself has to be propelled forward, so you need to put even more propellant.

It’s the same reason that space rockets are huge; the more propellant there is, the heavier the mass you’re propelling gets.

Wiki says… followed by this one


A Submachine gun (SMG) fires pistol rounds, and a machine gun fires rifle rounds.

For example, the Thompson Submachine Gun (“Tommy Gun”) fires .45 ACP, which is the round used in the M1911 pistol. If you have an M1911 and a Tommy, you can transfer ammo from one to the other, and also reload from a single ammo supply. Depending on the situation you are in, this could be helpful. When you go out shooting, you don’t need to put in separate orders for ammo for both guns - just get a total number of bullets fired and order that amount.

Likewise, there are several SMG’s that fire 9mm pistol rounds, like the MP 40, the H&K MP5, and the Sterling submachine gun, which was infamously used as the basis for the original Star Wars Imperial Stormtrooper blaster rifle.

Bingo. A pistol (or an SMG) is great for storming a building or drawing quickly for self-defense. A pistol (or SMG) is terrible for shooting tanks, sniping, or shooting across more than a small field. You have to get up close and personal for a pistol round to count. Now, if you have something like, say, a Garand, you’re effective at multiple football fields in length. Problem is that your gun is large and heavy. You can’t win them all.

I don’t think the second part is true. The propellant doesn’t have to propel itself - it all gets burned in the cartridge & barrel. The bullet itself doesn’t take any propellant with it when it leaves the gun - it’s not like a rocket at all.

There’s a lot of inaccurate terms being used by people in the media and elsewhere here’s the history behind the terms:

Prior to the Gatling and Maxim guns, you had 2 basic infantry weapons- the rifle and the pistol, which fired different rounds. Rifles typically had higher velocities for accurate fire at longer ranges, and pistols typically fired shorter, less powerful rounds for controllability when fired from a pistol.

The Gatling and Maxim guns were the first to fire rifle-caliber rounds automatically, so in a sense, they provided the firepower of a whole bunch of riflemen at once. They were the first machine guns, in that they were firing rifle cartridges in a fully automatic fashion. (if you want to get really technical, the Maxim gun was the first real machine gun, and the Gatling was something else).

During World War I, the rifles of the day were bolt-action, meaning that the soldier had to work a lever attached to the bolt to eject the spent cartridge case and load a fresh one before he could pull the trigger and fire a shot. In addition to that, full sized rifle rounds like a .30-06, .303 British or 8mm Mauser kick relatively hard, and have effective ranges of at least 1000 yards.

There was a need for a more handy weapon with more firepower for trench clearing, than the standard rifles of the day. So at first, they adapted automatic pistols like the P08 Luger to fire fully-automatic, and they quickly evolved into purpose-built weapons that were a little more rifle-like. These were the first sub-machine guns. They were fully automatic, short, relatively light, and fired pistol rounds.

So after WWI, there were machine guns like the Browning M1919, Vickers gun, MG08, rifles like the M1903 Springfield, the British SMLE, the German K98 Mauser, and the Russian Mosin-Nagant, and pistols like the Colt M1911, Browning Hi-Power, Russian Tokarev and Walther P38.

The Americans and Russians fielded the first self-loading rifles shortly before WWII- the M1 Garand and Tokarev. These rifles still fired the same full-sized rifle cartridge, but didn’t require the soldier to manually work the bolt to eject the old round and chamber a new one.

During the war, the Germans came up with a sort of hybrid- the Sturmgewehr-44 (literally “Assault Rifle - 44”). This fired a round that was the same diameter as the standard German rifle round (7.92mm), but that was significantly shorter and less powerful. This was the first “intermediate” cartridge, in that it was somewhere between a full sized rifle round and a pistol round in terms of power, range and size. This enabled the rifle to be fired controllably on full-automatic, much like a submachine gun, or fired accurately at much longer ranges than a submachine gun (although not quite as far as the older full-size rifles). The Sturmgewehr-44 was the first “Assault Rifle”.

After the war, the Russians adapted the concept into the AK-47, firing the 7.62x39 round, which is the same diameter as the full-sized 7.62x54 rifle round previously used, but that was quite a bit more controllable, smaller and lighter, allowing for fully automatic fire.

NATO went with the 7.62x51 round (adapted from the .308 Winchester), which is shorter than the older .30-06, and lighter, but isn’t significantly less powerful or controllable. The resulting rifles weren’t really “assault rifles” as such, and are usually referred to as “battle rifles”, since they’re essentially product-improved versions of the self-loading rifles like the M1 Garand, Russian Tokarev and German Gw-43.

Then the US went in a different direction with the adoption of the M16, by adopting a smaller-caliber rifle round- until then, rifle cartridges had been in the 8mm-7mm range, and the M16 fires a very high velocity 5.56 mm round, albeit quite a bit less powerful due to the lighter weight round than the older 7.62 NATO round.

The burned propellant immediately behind the bullet has the same velocity as the bullet; the propellant at the back of the brass has zero velocity. The average velocity of the propellant is, therefore, approximately 1/2 the velocity of the bullet. I say “approximately” because you would only expect this to be perfectly true if all of the propellant burned instantaneously; since the burning actually takes a fair bit of time, the average velocity of the propellant may deviate from that simplistic estimate.

Bottom line, it is true that the bullet isn’t carrying an on-board load of propellant when it exits the barrel, but the velocity of the propellant is most definitely far from zero, and must be taken into consideration when determining propellant load versus bullet mass versus desired muzzle velocity.

I believe the US tried the “battle rifle” concept for a while with the M-14, which I think still is in use by some special forces units, but changed to the M-16 for most purposes.