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Discussion » Questions » Science and Technology » What is the diff between a semi-automatic and fully automatic weapon in terms of how many rounds per minit? ?
RosieG

What is the diff between a semi-automatic and fully automatic weapon in terms of how many rounds per minit? ?

Does fully automatic kill twice as many twice as fast as semi? Arithmetic or geometric progression? Are there double fully automatic weapons? Gun-ignorant folks wanna know these things.

Posted - October 6, 2017
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Responses


  • As  99  said.  Semi automatically rejects and loads a round but only fires once per trigger pull.  Full-auto keeps firing as the trigger is held down. Traditionally, most often from an open bolt but there are closed bolt autos and open bolt semi's, though open bolt semi's are now illegal for manufacture in the U.S. because they are to easily converted.
    That's where we get into the reasons bump stocks are legal.  According to ATF regulations a gun  is legal for all lawful citizens if each round fired requires a trigger pull. Bump firing was a trick shooting technique with regular semi's and but recently people started making stocks that make it easier to do from a regular shooting position but even with them it requires a certain touch and fitness to work. When the rules were written bump stocks weren't  a thing or even an idea. People developed them to simulate full auto. Albeit in a hard to use manner. Since each round fired is the result of a single trigger pull, the legalities allow them as the firearm is still cycling in a completely semi-final manner.
      October 6, 2017 3:30 PM MDT
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  • 113301
    Thank you for your information-filled reply Glis and Happy Saturday.
      October 7, 2017 3:16 AM MDT
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  • 6023
    There are 3 types of firearms, when you consider this question.

    1 - Single action.  Think lever-action rifles, bolt-action rifles, old double-barrel shotguns, or "cowboy" revolvers.  You have to manually cock the hammer each time you want to fire.  (single-shot firearms would also be in this category)

    2 - Semi-auto.  The firearm automatically cocks itself each time you fire, but you have to pull the trigger for each shot.

    3 - Full-auto.  The firearm automatically cocks itself, and you can fire multiple times with a single trigger pull.

    Rate-of-fire can vary between full-auto firearms.  (EG: A "Tommy gun" has a slower rate of fire than a M-16.)
    Some you can switch between single-shot, 3-round burst, or full auto (fire until the magazine is empty).


    EDIT: "bump" firing a rifle is basically the same as "fanning" a single-action revolver.  You hold the trigger back, and do something to rapidly cock the hammer ... so as soon as the hammer is cocked, it releases and falls on a round. This post was edited by Walt O'Reagun at October 7, 2017 3:44 AM MDT
      October 6, 2017 3:35 PM MDT
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  • Wrong on so many levels.
    Single action is in reference to handguns. Even semi-autos can be single or double action. Colt 1911 is single- action for example.  All it means is that the trigger does not cock the handgun.  Bolt actions are just bolt actions. Same as lever actions.
    Wrong too about bump firing. You don't hold the trigger down. Actually you keep your finger off of it and pull the weight of the gun with your forearm into your trigger finger. The recoil causes the gun to keep "bumping the trigger against your stationary finger.  You do nothing to cock it the hammer and the vast majority of semi-auto long guns don't even have a hammer but are striker fired.  That's how bump stocks are classified as legal,  the shooter isn't holding the trigger down to fire. It is firing one round per trigger pull.
      October 6, 2017 4:34 PM MDT
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  • 6023

    Sorry ... You're wrong.  Semi-autos are neither single nor double action.

    "Single Action" refers to the fact that you have to manually cock the hammer for each shot.  (loo up the definition)

    And a Colt 1911 is NOT a single-action ... it is a semi-auto pistol.  After each shot, the gun cocks itself and another pull of the trigger fires it.

    A "double action" requires a trigger pull to cock the hammer AND fire the weapon.

    Your explanation of "bump firing" is just another way to do it.  But in essence, you keep the trigger depressed and recock the hammer in rapid succession.  Yes, you cock the hammer by firing the gun ... and your finger on the trigger fires it.  As I stated, you can do the same thing by "fanning" the hammer.

      October 7, 2017 11:51 AM MDT
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  • 2500
    Sorry Walt, but you're wrong, You seem to be confusing the loading action of a weapon with the cocking and trigger action of a weapon. That "single action/double action" thing refers to the trigger and firing mechanism. It has nothing to do with how the weapon is loaded or how may rounds it can fire in rapid succession. 

    Single action refers to the fact that the trigger mechanism is NOT capable of first pulling back the hammer to "cock" the weapon just prior to the weapon being fired. It can only release the hammer if the weapon has been previously cocked, its "SINGLE" action. So while the Colt Single Action Army revolver is, indeed "single action" in that the hammer has to be physically pulled back by the marksman prior to firing, so is the Springfield Armory M1911A1 (also made by Colt and a dozen other armorers to that Military specification). If you have any doubt about that please read the very first line of the Wikipedia entry on that particular handgun.

    https://en.wikipedia.org/wiki/M1911_pistol

    The difference is that the M1911A1 is usually first "cocked" by the marksman when the slide is operated to chamber the first round. Or by the thumb of the marksman should he or she have previously de-cocked it for some reason after chambering that round. When it is fired the consequent operation of the slide cocks the weapon for the next shot as well as chambering the round for that shot, and so on. But if that weapon has been de-cocked while a round is chambered pulling the trigger all day long will not cause it to fire.

    Double-action means that pulling the trigger is actually cocking the weapon immediately prior to the weapon's discharge. In this case the trigger both cocks the weapon and causes it to discharge, that DOUBLE action. "Hammerless" or internal hammer revolvers are a good example of the employment of this type of trigger mechanism.

    And then there's the single action/double action trigger. That's where on the first pull of the trigger the gun is also being cocked if it's not already. But the weapon can also be cocked beforehand. A number of modern revolvers with an external hammer have this type of trigger. One can pull back the hammer with the thumb prior to firing each round or can elect to just pull the trigger allowing that mechanism to cock the weapon immediately prior to discharge. And many modern semi-automatic pistols have that kind of trigger too. And in the case of the semi-auto pistols the previous round fired operates the slide to cock the weapon for that next shot.

    The advantage of the double-action trigger is that a loaded weapon is always ready to fire, no worry about having to cock it prior to firing. The disadvantage is the much higher "trigger pull" required to actually fire the weapon (12-pounds is typical) as well as to chamber that next round.

    The advantage of the single action trigger is that of a much lighter trigger pull that is needed to fire the weapon, (down to that old legendary "hair" trigger) with 4 to 6-pounds being typical.

    The single action/double action trigger enjoys the best of both worlds. And as an added bonus semi-auto handguns thus equipped usually include a de-cocking lever to safely de-cock the firing mechanism.
      October 8, 2017 5:47 PM MDT
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  • A 1911 is a single action auto.  With a round chambered the hammer needs to be cocked to fire. a round can be chambered and the hammer uncocked but the gun will not fire by trigger pull without first cocking the 1911 hammer.  Each subsequent shot recocks the hammer unless it is manually lowered.  Automatic handguns come in both single and double action as well as double action only.

    My explanation of bump firing is the only way to do do it and it is nothing like fanning a hammer on a single action revolver and one does NOT hold the trigger down.  The trigger is being rapidly pulled by the recoil of the weapon and there is one trigger pull  for each round fired and that's why they have been legal under BATFE regulations.

    BTW: there is no hammer in the AR style weapon used in this tragedy.   They are spring loaded striker fired.


      October 9, 2017 5:14 PM MDT
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  • 113301
    Thank you for your extremely helpful and informative reply Walt. You stated it very clearly so now I understand the differences. I appreciate the time you took to educate me and any others who were uninformed. Happy Saturday to thee!
      October 7, 2017 3:45 AM MDT
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  • 22891
    not sure but they both do the same thing which is kill people
      October 6, 2017 3:55 PM MDT
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  • 2500
    For the sake of the discussion we'll assume that you're referring to trigger-fired, single-barreled weapons that are under the direct physical control of the operator and are self-loading courtesy of part of the energy expended when the previous round is fired . . .

    [There is a class of "rotary" machine gun that is operated remotely by an external electric motor. Examples would be the M134 minigun in 7.62-mm / .30-caliber (same as the M60 machine gun described below) and the M61 20-mm (a little over 3/4-inch in diameter) Vulcan "canon". Both have selectable throughputs of between 2,000 and 6,000 rounds/minute. Don't expect to see one at the local gun range though. The purchase, care and feeding of such requires the wealth of either Bill Gates or your favorite Uncle back east.]

    The "throughput" speed of more conventional fully automatic weapons varies greatly depending on the model of weapon and the cartridge that it's "chambered" for. The rate can vary for a few hundred rounds a minute up to almost 2,000-rounds per minute. A few well-known examples are the  M2A1 50-caliber machine gun that can fire at a rate of from around 450 rounds/minute to approximately 600-rounds/minute. Its smaller cousin the M60 .30-caliber machine gun has a similar firing rate, 500 to 600-rounds/minute. The .22-caliber M16 (not to be confused with it's look-alike, chambered alike cousin the AR-15) fires at between 700 and 950-rounds/minute when set to full auto. And the .30-caliber AK-47 is a tad slower than the M16 at around 600-rounds/minute. There was even a .22LR machine gun in development for use in Vietnam at one point. And with automatic weapons like that once a magazine is inserted in the weapon and the first round is "chambered" all one has to do is to simply pull the trigger and hold it and it will start to fire and continue to do so until 1) the trigger is released, 2) the magazine runs out of ammo, 3) the weapon "jams" or 4) the barrel "droops" from becoming hot from all that shooting (which may well cause the weapon itself to blow up). 

    When operated in semi-automatic mode where the gun will only fire one time the trigger is pulled no matter how long it's held in the "pulled" position, won't fire again until the trigger is released and then pulled again, the throughput speed is greatly reduced. Typical speeds are more in the neighborhood of 50-rounds/minute (there may be a few people that have nervous twitches that can fire them them faster, but not by much). But again, that can vary by the gun, the caliber of the ammo and the skills (or lack thereof) of the marksman.

    Another thing that you need to keep in mind is the actual capacity of the magazines that hold the ammo. An M16 with the "standard" 30-round magazine can only sustain full automatic fire for all of about 2-seconds. Then you've got to change magazines and chamber another round to start firing again. Even the 50-round magazine will only give about another second. The M2A1 and the M60 are a bit different in that they are "belt fed" and due to that can have available thousands of rounds to fire (the "belts" can be linked, ammo can to ammo can). But even then the barrel of the weapon will soon heat to a point where the gun becomes unusable if fired continuously. 

    There's a disturbing tone to your question though. You seem to incorrectly think that every shot fired from a weapon will kill someone. That's simply not true. In fact, MOST bullets fired from any given weapon will not even find a fleshy target let alone mortally wound it. And machine guns are the WORST for that task, contrary to what Hollywood would have you think. Unless tripod-mounted they rapidly "walk" off the target due to the continuously repeated recoil and the actual "sighting" accuracy is soon lot due to the barrel warping from the heat build-up. One thing that they are good for in a combat situation is keeping the enemy soldier's heads down while your side groups for the offensive (or the defensive). I'm told by friends that had the displeasure of being foot soldiers in 'Nam that it was common for them to take two 50-round M16 magazines and tape them together. They would fire in "Full Auto" in the general direction of the enemy with the first magazine which had the effect of the enemy taking cover then flipping that magazine pack over and repeating. But as the second magazine started to fire the other members of the patrol would pop up to see when the enemy soldier might be. When those enemy soldiers did start to pop back up after the second volley they were easy targets. 
      October 6, 2017 5:09 PM MDT
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