Ironman knows much more about many small-arms related topics than the rest of us, but some of us are confused and need some things explaining.
Firstly, I still don’t understand this comment - could you please explain it to me?
In a pistol, the 9mm was good, but in 1940’s era SMG’s it was not so good. The energy from the smaller round must be used to operate the hammer, and that can lead to jamming and weak hit power.
So what your saying is that a 9mm parabellum fired from an SMG is less powerful than a 9mm parabellum fired from a pistol? Why? I just don’t understand it.
When Ironman’s satisfactorily explained this, we can ask him other questions that have been bothering us.
I will thus answer the question for him, and thus clear up the falsehood which he propagated and that Guddha unfortunately absorbed:
The self-loading mechanism does use energy from the cartridge, but it uses energy which is present it excess.
Some muzzle velocities (fps rounded to nearest 5):
9mm Para pistols - muzzle velocity around 340-350m/s (1115-1150fps)
9mm Para SMGs - muzzle velocity around 380-390m/s (1245-1280fps)
The INCREASE in velocity from the SMG is due to the longer barrel giving the bullet longer to accelerate. The self-loading mechanism does not take any power away from the bullet.
And we also have an excellent comparison, with two weapons firing the same cartridge through the same length of barrel, one being a bolt-action, the other self-loading:
From: Hatcher’s Notebook p. 255, Maj. Gen. J. Hatcher (retd), 3rd edition, Stackpole, 1962
Data reported by Aberdeen proving ground when Hatcher was chief of the Small Arms Devision Technical Staff in 1930:
So, no reduction in muzzle velocity (and therefore power) is measured at all from the Springfield to the Garand.
Thus, the following additional statement made by ironman on Thurs 26 May is manifestly wrong and misleading:
Even a civilian knows that a revolver or bolt action weapon is more powerful per se because the energy from the exploding gases of the cartridge is not used to power the action of such a weapon.
We are dealing here with Newton’s third law of motion, in that for every actions there is an equal and opposite reaction.
Now in simple terms this means that if you are in a boat and you push against someone on shore he will fall backwards and you will drift out to sea for a short distance.
Obviously he has feet on the ground providing greater friction whilst you are on fluid and hence you move more than he does.
Transfer this to a blowback weapon and the results are interesting.
If the weapon has no spring the moving parts jump to the rear and stay there. The round however travels a fixed distance based upon choke of the barrel, and energy created by the round discharging because the weapon is designed to utilise the waste exhaust gases to load the next round rather than the propellent force. Let’s call this distance 1D for the sake of simplicity, for we need simplicity here. The firer however gets a bruised shoulder because there is no spring to absorb the energy. This is the classic bolt action situation.
If the weapon has the correct spring the round generates sufficient recoil to move the working parts to the rear hence the next round is loaded but this is a purely post detonation situation and the round still travels 1D, not 0.75D because it has put a bit of effort into fighting against a spring.
If the weapon has a very strong spring the round generates insufficient recoil to move the working parts to the rear hence the next round is not loaded but this is a purely post detonation situation and the round still travels 1D, not 0.75 D because it is really tired after fighting against this really naughty big spring.
I never claimed to know more about weapons than anyone. However, having researched the problem of weapons jamming a number of times by asking people who sell guns, numerous hunters, and people who use them professionally (soldiers and cops), this is what I have learned over the years. I hope it helps:
The 9mm round in an SMG is more succeptible to jamming, especially when foreign matter is introduced into the action and in cold weather than those using a larger, more powerful round. This problem was more frequent in WWII SMG’s that used a 9mm round than those that used a larger round, but can also be seen in modern auto handguns. The .380 auto is an example of this - it is more prone to jaming than the 9mm, which is more prone to jamming than a .45. Smaller rounds will move the bolt backward slower, and because of the effect of spring tension, the bolt also returns slower. The reduced speed lends to the round not being fed as quickly, which means there is more time for gravity to pull downward on the round as it hits the feeder ramp, and that can lead to jamming more in a 9mm than in a more powerful weapon. Despite the fact that the cartridge weighs less than a larger calibre, it produces slower action, and the increased time is not a positive result.
The MP38-40 and Sten are perfect examples. Both suffered jamming problems, especially the Sten. This is due not only to design, but to the lower powered round. This is also why a .22 rifle will jam much more than a 30-06. Add to this imperfections in ammunition, and the occasional faulty, lower-than-normal powered round would lead to jamming much more often in a 9mm than in a .45, for example. The weaker 9mm round is also why the Luger had a steeper feeding ramp than other, larger calibre pistols.
.380ACP jams more easily in auto pistols than 9mmPara because .380 is short and stubby and therefore prone to stovepiping. It’s nothing to do with power (.380 ACP in a straight-blowback pistol gives a vicious recoil compared to 9Para from a locked-breech pistol) - compare the reliablilty of a .32ACP Walther PPK with that of a .380 ACP Walther PPK. .32ACP is much less powerful, but is more reliable because it is less prone to stovepiping.
The Sten’s jamming problems are largely due to the magazines often being of poor quality.
Gravity’s impact on feeding is zip - the cartridge is usually not fully released by the feed lips until it’s mostly chambered.
The speed of the bolt in an SMG varies with the cartridge pressure, bolt mass, and spring constant. A .45ACP M1 Thompson’s bolt moves faster than the 9mm STEN’s which moves faster than the .45ACP M3 “grease gun”'s. This is evidenced by the rate of fire. In fact, the fastest moving SMG bolt is probably the .380 ACP MAC 11 (1600rpm), which is one of the weakest cartridges used in an SMG.
What on earth does the angle of the feedramp have to do with the power of the round? My 9mm pistol (Pardini GT9) has a vestigal feedramp because the magazine design presents the cartridge very high. The Luger mag design presents the cartridge very low. .38 Super M1911s are more reliable than .45ACP M1911s because the .45ACP is more prone to stovepiping (the bigger round has its centre-line positioned lower in the magazine when feeding).
There are .22 cal rifles which almost never jam - if I’m running the right ammo in my Ruger 10/22 (SK, for insance), it can run without a stoppage for about 500 rounds without cleaning (IIRC my record was about 1000). Do that with a .30-06.
Please provide a cite for your claim that underpowered ammo in a 9mm is more likely to cause a stoppage than underpowered ammo in a .45, sounds like bollox to me (like most of the rest of your post).
I don´t know enough about the MP38/40, but I did quite a bit of research about the Sten (I own a deactivated Sten MK2).
The Sten Mk2 had two weak points:
a) The magazines. Since the powers that be in 1941 decided that the Sten had to be able to accept the magazines of the Lanchester MP, which was a copy of the German Bergmann MP28, it had to work with a magazine design, which was already obsolete by this time. The Lanchester /Sten magazine (BTW almost the same as the magazine of the MP38/40) was a single stack magazine. This caused a lot of friction between the walls of the magazine body and the rounds, if a little dirt got mixed in, the magazine spring wasn´t strong enough to push the rounds up. A first fix was not to fill the magazines to the nominal capacity, e.g. only to 28 rounds instead of 30. The British Indian Army had another fix and made the magazines very reliable in this aspect by soldering 4 pieces of brass wire into the magazines to act as guides for the cartridges. The follower was modified as well. This reduced the magazine capacity to only 19 rounds, but feed problems through the spring not being able to push the rounds up were gone. I´ve also heard some reports from guys, who modified a Sten to accept the double stack magazines of the Sterling SMG (the mod consisted of altering the mag well and the feed horns on the bolt). This increased the reliability greatly.
The bottom magazine is an original British one, while the top one has been modified in India. You can see the ends of two of the brass wires at the lower end of the magazine.
The original Sten magazines had another weak point:
To feed properly, the cartridge has to be held by the feed lips at an angle of 8.5 degrees, so that it can be picked up by the feed horns on the bolt and pushed into the chamber. If the magazine feed lips are bent just a little (and they were made of very soft steel due to wartime shortages), the round will not be picked up properly and will jam somewhere between the barrel bushing and the bolt.
The Israelis fixed this problem after WW2 by first sorting all the magazines, so that only good ones stayed in service and then case hardening the feed lips, so that they didn´t bend as easily.
b) The other weak point on the Sten MK2 and the Stem MK5 is the attachment of the magazine well. On both guns it can be rotated on the receiver tube. The reason was that, with the magazine well rotated downwards (works only without a magazine in position), the guns take less space in storage (important for shipping) and the ejection port is covered, preventing the ingress of dirt.
When ready to fire, the mag well is held in the correct position by a springloaded plunger attached to the front of the mag well. If the gun is being held by the magazine when firing (as often seen in Hollywood movies) and not on the barrel shroud like a rifle (as per regulations), the vibrations will wear out the plunger very fast. As we have seen, the proper feed angle is critical with the Sten, so this would lead to stoppages.
Another problem is that the inner end of the plunger has teeth matching the teeth on the barrel nut. They secure the barrel nut and barrel in position. If they are worn out, again by holding the gun on the magazine, the barrel nut will become loose during firing, leading to stoppages. This is also the reason why the foregrip of the Sten MK5 was abolished after a short time in service.
This picture shows the plunger in detail:
Here another shot from the top, with a magazine inserted:
This picture shows the mag well folded down, you can see the hole in the receiver tube, where the plunger engages and the teeth of the barrel nut.
Here you can see the barrel nut with it´s teeth:
So you can see that the jams had nothing to do with the strength of the cartridge or the calibre (there have even been .22 cal SMGs built in the past). The mass of the breech block and the strength of the main spring have been calculated to give it exactly the correct speed for proper extraction of the empties, the feeding is solely done by the main spring.
A .45 cal SMG needs correspondingly a heavier breech block and/or a stronger main spring.
Jan
Disclaimer (to whom it may concern): The Sten submachine gun depicted in the pictures has been deactivated in accordance with the applicable German laws (Dekowaffe) and is neither able to chamber or fire a round.
True about the .380. However, lighter, lower powered rounds jam more frequently in general.
That is not true for all weapons, or weapons in general. You are comparing one particular firearm to another.
It has to do with the ability to jam. The steeper the angle, the better the chance of jamming, regardless of the height of the feed.
You can do that with many weapons. I’ve done that with a Marlin 989M2 as well. I have three .22 calibre rifles and a .22 calibre pistol in my gun collection, and larger calibres too. It has been my experience, as well as the many hunters and spelunkers I have known, that a smaller calibre gun jams more frequently than a larger calibre gun.
Now, you would be making a mistake if you thought that jamming occured frequently with any firearm. It just does not happen much, unless you are using a cheap weapon (Not I) and chap ammo. Then jamming will be far more pronounced. Comparing one particular weapon to another for jams is folly, because jamming varies considerably depending on many things. The big picture is however, that smaller rounds jam more frequently. I have seen a .22 fire only 100 rounds and jam 3-4 times when whistle clean. I have also seen a 30-06 do the same. Conversely, I have seen both fire hundreds of rounds without a jam.
Police forces around the world have been frustrated by jamming problems with high quality 9mm’s, even when the weapons are of the highest quality brands, such as Glock (over-rated), S&W, Colt. I am somewhat surprised that you seem to not be aware of the fact that the 9mm has been traditionally a less reliable round than that of the .45. Particularly since WWII era 9mm’s were more unreliable than they are today.
The Sten was designed around 9mm Para ammo, because at this time the British forces had captured a huge stock of Italian ammo. It was also thought to be of advantage to be able to use captured German ammo, especially for resistance groups operating in occupied countries. At the time of the design of the Sten, Britain didn´t manufacture any 9mm of her own, though there were small stocks of ammo for the Lanchester SMG used by the Royal Navy in small numbers.
Concerning jams, you have to distinguish between feeding jams and extraction jams. The later can be caused by a malfunctioning extractor or by the case getting stuck in the chamber. The more conical a case is, the less is it prone to jam (compare the Russian 7,62x39 and 5,56mm Nato, which is more likely to get stuck in a dirty chamber?) on extraction.
The 9mm Para has a slightly conical case.
Then there is the problem of primary extraction. Since at the opening of the breech there is usually still residue pressure inside the case, pressing the walls against the chamber, a fast movement of the breech will easily tear off the bottom of the cartridge. Most guns use the unlocking movement to start pulling slowly on the case. Some guns, like the delayed blowback designs of H&K and CETME require to have flutes milled into the chamber close to the cartridge mouth to provide a thin film of gas between the case and the chamber wall, because else the very violent action of the bolt would tear the cases to pieces.
Concerning feeding problems, this depends largely on the shape of the bullet, as it slides up the feed ramp (feeding is accomplished solely by pressure of the main spring of the gun, the power of the cartridge has no influence on it). Most military SMGs are designed to work well with the military steel or copper jacket round nose bullets. If you use different bullets, e.g wad cutters or hollow points, they might jam.
I agree with everything you said, except one thing. And well stated too. I do still contend from personal experience and that of many associates who are shooters that a lower powered round jams more, and that the weight of the cartridge plays a small part of it. Feeding jams are more frequent with smaller callibre than extraction jams because the round weighs less and is more succeptible to movement during the feed. The heavier the round, the less suceptible to this it is. I agree with you as well man of Stoat, that the short rounds jam easier. This is true of a 9mm particularly.
The very conical, but relatively short 7,62x39 case has less problems with extraction than the almost cylindrical 5,56 mm Nato, simply because after the first tenth of a millimetre movement of the case, it clears the chamber very quickly and produces almost no friction, while a cylindrical case will rub against the chamber walls for almost the whole travel. This is one thing, which makes the AK47 so reliable, even if it gets dirty.
Feeding jams are only depending on the geometrical configuration of the magazine feed lips, the cartridge and the bullet shape, the feed ramp and chamber shape and the shape of the bolthead / slide head. Cartridge weight might play a little role, especially i how fast a new round is being pushed up by the magazine spring.
If you use a 9mm pistol or SMG, which has been designed for military roundnosed FMJ rounds with soft lead bullets, wad cutters or hollow pointsm you will in many cases experience feed jams due to the different shape of the bullet. The same will apply to .45 cal guns, if used with ammo they were not designed for.
:shock: 
