What is the recoil of a submachine gun like, and why so few calibers

Almost all the submachine guns listed are 9mm, is there a reason for this? There are a few 40s, but almost no 380, 22, 357, 25 etc calibers.

Also are submachine guns easy to control enough that you don’t have to fire in burst mode? With a fully auto rifle you’re supposed to fire a few shots at a time, with a submachine gun can you just hold the trigger down and control recoil enough to hit your target?

In this video, a guy uses an American 180 which fires .22 bullets in fully auto mode, and he seems like he has fairly good control over it. Granted he doesn’t hit his target (which is about a foot tall) but most of his bullets are within a foot or two it appears.

One flavor or another of 9mm (most usually 9x19) are the standard military issue handgun cartridges for virtually the entire world post-WW2 and especially since the latter half of the Cold War. So of course if you want to sell SMGs, you’ll make them nines.

Pre-WW2, and afterwards into the 60s by inertia of “installed base”, various forms of 7.65mm/7.62mm/.32ACP pistol round were also very common for civilian or police issue abroad so there were many in those loads (e.g. the widely distributed Russian PPSH and the CZ Skorpion machine pistol)

Since for the Americans the standard military pistol round until the 80s it was .45ACP (M1911, Tommy Guns, M3s), a bunch of models were made in that chambering.

Otherwise not much of an incentive for making other calibers.

We only had a few hours one day on the MP5 (9mm), but as I recall it was surprisingly easy to handle (compared to our standard issue AG3 and the MG3 I’d tried twice.)

We were told to stick to bursts, but I wouldn’t be surprised if that was more about not wasting bullets on a target you already hit, than it was about muzzle rise and accuracy.

I’ve shot a fully automatic Uzi, MP5, and a Sten. The Uzi was extremely challenging to control. The MP5 was quite easy. The Sten I shot was actually even better than the MP5 – I don’t know if that’s true for all its variants or just the particular one I had access to.

Just to emphasize, 9x19 aka 9mm Parabellum is the NATO standard for handgun and submachinegun rounds. If you want to sell to any NATO military, including the U.S., you want to chamber your weapon in the NATO standard round. Non-NATO military forces as well as police and paramilitary forces often standardize on NATO standards, due to a combination of factors (it’s what the “big boys” are doing, there’s not much of a need to independently trial weapons that have already passed U.S. and NATO military trials, military in-kind aid and military surplus from the U.S. and NATO militaries by definition use NATO standard rounds).

Plus, 9mm is just well-suited to the specialized functions that professionals would use submachineguns for. .45 ACP has a lot more recoil and the extra power tends to be over-kill (not many targets will survive multiple hits from 9mm rounds). Rounds with more penetration than 9mm will tend towards over-penetration, which is dangerous to hostages, bystanders, and other “friendlies” in the close-quarters submachineguns are used in, and so on.

Also, the Soviet military, and militaries that followed their doctrines, didn’t have much use for submachineguns. To be sure, during WWII, the U.S.S.R. fielded a lot of PPSh-41 submachineguns, but that was generally used as an urban combat assault weapon and proto-assault rifle, not for the more specialized functions most of those 9mm submachineguns are intended for. After the AK-47 was fielded in c. 1947, the Soviet military largely stopped developing and fielding submachineguns, since the AK-47 filled the role they were using them for. So, post WWII, with only a couple of exceptions, the design and development work on submachineguns was pretty much all for the Western military and paramilitary market, which, as stated above, standardized on the 9x19mm round.

I think I read once of a machine gun having an average thrust of 50 lbs. This is a pretty difficult force to deliver. That is, you’re not going to just stand there as if nothing’s going on, you’re really going to lean into it.

For some reason, web searching “machine gun thrust” turns up a bunch of oddball stuff…

It’s pretty much been answered. 9mm is so common because it’s the NATO standard. Also, to answer your other question, “yes”. One can easily empty an entire magazine with an MP5 and keep it on target.

I don’t know what they were measuring, but it wasn’t the recoil. 50lbs is way too much.

This table gives 70 ft-lbs for the .50 BMG (647g @2710)

I’m not really sure how to respond to this. Should I average all of those numbers to see how close to 50lbs we get? Should I point out that nobody is shoulder firing a .50 cal machine gun, so there’s no “lean[ing] into it” necessary, or should I just say that the 50 BMG isn’t relevant in a thread about submachineguns?

That’s energy of 70 ft-lbs. Which is among the standard three measures of recoil, recoil impulse (momentum of the gun), recoil velocity (how fast the gun would go with nothing holding it) and recoil energy. I don’t know of any standard measure of ‘thrust’. But anyway felt recoil for a given gun and shooter is subjective. It defies exact measure and calculation. The standard measures just give an indication if one gun has way more recoil than another.

But since the weight of the gun relative to the weight and velocity of the bullet is a key factor, it’s obvious that felt recoil of classic submachine guns is lower than pistols firing the same cartridges. For example an M3 SMG weighs around 9 lbs so no subjective ergonomic difference is likely to wash the difference between that and a ~2 lb M1911 pistol firing the same .45 ACP round, felt recoil of the SMG will be lower per shot. Although, you’re trying to control the M3 in (albeit naturally slow cyclic rate) automatic fire… then again that’s not just about the ‘kick’ of recoil.

Even a modern SMG like the MP5 weighs ~7lbs, an obvious advantage in felt recoil, on semiauto certainly, compared to a 9mm pistol, even if the longer barrel gives somewhat more velocity to the bullet.

And, WWII rifles were generally around the same weight or only a little lighter than contemporary SMG’s but fired bullets in the same general range of bullet weight which went much faster.


The HK MP5 is particularly noted for its controllability, but I have personally fired an S&W Model 76 (which is basically an updated Carl Gustaf m/45 in 9mmP) and managed to keep all of the rounds on a B27 target at 15 meters. You are naturally going to get some drift just because the gun is shaking in your hands but keeping the barrel pointed at the target doesn’t require superhuman strength as long as you are using both hands.

I’m not really sure what that table means. A .50 BMG round has a muzzle energy of between 10,000 and 15,000 ft-lb[SUB]f[/SUB] of energy; how that gets translated into effective recoil depends on the mass of the rifle, the effectiveness of the muzzle brake and/or recoil buffer, and the geometry of the rifle. I have only fired a few rounds from a single shot .50 BMG rifle with a large brake from a prone, bipod supported position, and I could say that I would not want to fire that gun in a standing position. On the other hand, I’ve fired 12 gauge 3” magnum slugs and while I would not describe the experience as pleasant, it didn’t threaten to knock me over or leave me with a severely bruised shoulder.

The reason there are so few caliber selections in submachineguns is that the market for these weapons is really pretty limited to military special operations, paramilitary security forces, and police special tactics where the compactness of the weapon outweighs the relative ineffectualness of pistol-caliber rounds. (Semi-automatic versions and quasi-submachineguns are sold on the civilian market in some places but being semi-auto and generally of inferior quality they aren’t really a particularly better choice than a pistol or pistol-caliber carbine for defensive use, and generally are poorly suited for plinking.) You will find a handful of guns chambered in calibers below 9mmP (as listed above) but these are mostly curiosities or fall into the domain of so-called “personal defense weapons” intended to be carried by tanker crews or non-front-line personnel for whom a rifle-caliber weapon would be too unwieldy, and while there have been a few efforts to chamber submachineguns in .40 S&W and 10mm Auto, those calibers have never found wide adoption outside of the United States whereas the 9mmP (and to a lesser extent the .45 ACP) are nearly ubiquitous. The 5.7x28mm FN and the 4.6x30mm HK are intended as replacements for “pistol caliber” rounds that are suitable for use in battlefield against opponents with soft body armor but their terminal effectiveness is inferior compared to jacketed hollowpoint (JHP) pistol caliber rounds against an unarmored target.


I was in an armor group in the Vietnam era. We had .45 handguns and also what they called a gas powered automatic burp gun. Looked like a caulking gun. When firing, and it was a hoot, it tended to ride up.
They recommended firing it horizontal.

I was on a SWAT team in my younger days and the MP5 was our shoulder weapon. As other have noted, it was very easy to control. You could dump an entire 30 round “burst” onto a Q target from 25 yards if you set up for it - proper stance, concentrated on staying on target etc. That said, there is no practical application for such a thing. Later models had a three round burst option. All three rounds would strike very close to each other before the muzzle had a chance to wander very far.

Submachine guns were originally devised around the WWI time frame as something more effective for trench-clearing than your bolt-action rifle of the day. They fired pistol cartridges, because they were plentiful, weren’t high recoil, and were relatively small- in effect, a SMG is a fully automatic carbine firing a pistol cartridge.

I’ve personally fired a Thompson, STEN, MP-40, and a M3 Grease Gun. The STEN was far and away the most accurate, with the Thompson not too far behind, at the cost of quite a bit of weight and size. The M3 was more like a shotgun, and the MP-40 was closer to the Thompson/STEN than to the M3. The recoil was negligible on all of them. Muzzle climb was the main issue- they all had a tendency to ride upward- after about 3 rounds, and I wasn’t even close to on target. Hence the advice to fire in bursts.

As for actual machine gun recoil… while they fire the full-bore cartridges (I fired a M1919A6, a BAR, and a MG3 (MG42 chambered in 7.62 NATO)), and despite firing more rounds, something about the weight and action and rate of fire made it distinctly less punishing than firing the same rounds out of M14/FAL/M1 Garand rifles for some reason. The MG3 in particular had more of a vibrating push feel, than feeling individual rounds fire. So did the M1919A6, but with the lower ROF, it was less of a vibration, and more of a stutter. I had to lean into both though. The BAR’s weight made it surprisingly controllable and comfortable, oddly enough.

  1. This was mentioned at least once before, ie that the US Army believed the M3 was more controllable and accurate than the Thompson and more still compared to the MP40, as shown in this film. Which could have had a ‘propaganda’ element, OTOH it was comparing new rather than decades old weapons. But I think more likely it’s just the subjectivity of this whole topic. Other people might have the same impression as you, or not.
  2. That’s what physics would predict: the recoil energy of the BAR is around half that of the M1 rifle because it weighs around twice as much firing the same bullet to around the same muzzle velocity. Or in an auto-auto comparison a BAR should be easier to handle than a full auto M14 despite the slightly less powerful cartridge of the M14. A true light machine gun would in turn generally be even heavier so more manageable firing the same rifle cartridge, hand held, as long as the shooter can hold it up (obviously easier to control with bipod or tripod).

On a big picture level it’s obvious when one weapon is twice (or several times as in SMG’s v pistols) as heavy but firing the same round: it will have less felt recoil. In cases where the weapons weigh around the same and fire fairly similar ammo (say M3 and MP40, though 9mm is a lighter bullet travelling somewhat faster than .45), then perception of recoil and controllability is likely to be more subjective, though opinions might be strong.

There’s no upside to using these feeble cartridges (357 not feeble, but rimmed so no good for automatic weapons). They do nothing that 9mm doesn’t do.

The upside is that you can fire them in a smaller automatic pistol/PDW with some degree of controllability versus a major power round. But the actual utility is pretty limited.

Forgotten Weapons: “Shooting the Czech vz61 Skorpion: Machine Pistol or PDW?”

Contrast to a fully automatic pistol firing a 9mmP round: Forgotten Weapons: “H&K VP-70M on the Range: How useful is the Burst Fire?”

Obviously, for a full sized SMG using a large caliber makes more sense, but if you want something that can fit in holster sizing down to a more controllable caliber makes sense. That being said, there is no reason to chamber any gun in .25 ACP. It’s continued existence is a complete mystery.


I don’t think that’s it; the nations that fielded them likely fielded them in the calibers of their standard pistol ammunition -i.e. 9mm during WWI, and 45 ACP in the US shortly afterward.

Using something like .32 or .380 or .25 would require them to have an entirely separate caliber of ammunition for no real gain vs. the pistol cartridges already in hand.