[QUOTE=Chefguy]
It’s just a damn shame you guys never actually built anything. 
Chefguy - former Seabee
[/QUOTE]
[hijack]
Yeah, we like you SeaBees – you help offload our stuff from the boats, 'cause yours is laid up in vehicle maintenance! 
[/hijack]
Tripler
Wait, what thread am I in?
[QUOTE=Shagnasty]
…and the Mach 10 would shoot nineteen .45 rounds a second. With a 50 round clip, you would burn through ammo very fast, too fast in my mind if you held the trigger.
[/QUOTE]
Nitpick: it’s a MAC-10 (Military Armament Corporation, Model 10). You’re not alone in making this gaff; I’ve seen it several times in novels of questionable technical province, including one of the Raymond Benson-penned James Bond novels.
Stranger
Full automatic is best used in the first seconds of an ambush that you initiate.
So in summary:
Thanks all!
My combat experience consists of paintball and Call of Duty 4. But in my experience, controlled bursts of full-auto fire are best used in close quarters when you don’t have time to take aimed shots. For instance, when breaching a door or bunker.
Based on my limited experience, submachine guns (Thompson, STEN, Grease Gun, etc…) are pretty controllable on full auto, and have rates of fire slow enough to squeeze out 3-4 round bursts without much trouble at all. And, in the close quarters that smgs tend to be used, full-auto is probably the right way to roll anyway.
Rifles, on the other hand, have enough recoil to make full-auto much harder to control, and probably better fired semi-auto at selected targets.
Machine guns don’t generally have selector switches, and if I’m not mistaken, are used more like a long-range shotgun with short 3-10 round bursts.
I would say ‘never’ fire on full-auto unless you’re firing fix-point or bipod-mounted ‘crew serviced’ weapons like the M-2 .50 cal HMG, M-60 7.62mm LMG, or M-249 5.56mm SAW - they’re heavy enough to stay fairly accurate when firing full auto, even though they’ll still bounce around a bit and scatter rounds along the axis of fire, and they come with 200+ round belts so you can sustain longer bursts without having to reload. Nearly any other full-auto weapon is simply too light; by the end of the magazine you’ll be “shooting ducks” (aka shooting straight up in the air) unless you’ve arms like Rambo. Even then accuracy is gone, so maybe the first 3 rounds are in the general vicinity of the target but the last 27 rounds in the mag are nowhere near it and basically wasted. The US M-16A2 / M4 (i.e. the new gun the troops are all carrying in the US, made by either Colt or HK) and the British SA-80, as well as the HK assault rifle series G36, all have a 3-rnd burst setting, meaning every time you pull the trigger you get 3 rounds down range, but still have a full-auto setting although it’s nearly never used. I don’t think AKs have a ‘burst’ feature, but they are generally much heavier so slightly more accurate in full-auto fire.
The biggest single reason to avoid auto fire, however, is that you’ll be out of ammo very very quickly. A single magazine for an M-4 series assault rifle like most US troops carry, fully loaded, weighs about a quarter of a kilogram and holds 30 rounds. Carrying 20 magazines is 5 kilos; the M-4 weighs about 4. That’s nearly 10 kilos for just your weapon and ammo. Full-auto will blow through a magazine in less than a second. Do you really want to be out of ammo in less than a minute when you’ve got a rampaging horde knocking on your door? I’d much rather conserve my ammo and pop lots of people charging at me - at least then the ones behind them might trip and fall or lose interest in dying 
Neat factoid:
The Thompson sub-machinegun of WW2 fame had what was called a Cutts Compensator on it which would force the muzzle blast out of one side of the barrel (the right side I believe); troops were taught to fire long bursts and the muzzle blast would force the weapon to go from right to left while it was being fired. This was excellent for suppressive fire, in that it was naturally strafing along a horizontal line and the .45 cal round was big enough with enough punch to knock down people fairly effectively so was very popular with trench- and fortification-clearing.
[QUOTE=GomiBoy]
I would say ‘never’ fire on full-auto unless you’re firing fix-point or bipod-mounted ‘crew serviced’ weapons like the M-2 .50 cal HMG, M-60 7.62mm LMG, or M-249 5.56mm SAW - they’re heavy enough to stay fairly accurate when firing full auto, even though they’ll still bounce around a bit and scatter rounds along the axis of fire, and they come with 200+ round belts so you can sustain longer bursts without having to reload. Nearly any other full-auto weapon is simply too light; by the end of the magazine you’ll be “shooting ducks” (aka shooting straight up in the air) unless you’ve arms like Rambo. Even then accuracy is gone, so maybe the first 3 rounds are in the general vicinity of the target but the last 27 rounds in the mag are nowhere near it and basically wasted. (…)
[/QUOTE]
Oh, come on. It’s simply not true. Sure, full auto fire is inaccurate, but you are exaggerating greatly. Reasonably trained shooter of average build can keep weapon sights within proximity of target without much trouble (at least when shooting machine pistols or small caliber weapons like M4). Cite:
random video of shooting full-auto from youtube - doesn’t look like shooting ducks.
[QUOTE=puppygod]
Oh, come on. It’s simply not true. Sure, full auto fire is inaccurate, but you are exaggerating greatly. Reasonably trained shooter of average build can keep weapon sights within proximity of target without much trouble (at least when shooting machine pistols or small caliber weapons like M4). Cite:
random video of shooting full-auto from youtube - doesn’t look like shooting ducks.
[/QUOTE]
ALL automatic fire makes the weapon jump and jerk and raise up; the longer you auto-fire and the lighter the weapon the stronger this force is. “Shooting ducks” is an exaggeration, but the fact remains - autofire with an assault rifle is hugely inaccurate. I would only think it was useful in a very very small number of circumstances, and only as a last resort. It’s contrary to most small-arms combat training anymore, and largely a thing for movies and video games. Your video shows guys fucking around in the field, not on combat maneuvers. It’s just dumb to autofire with an M4 in any normal combat situation.
I’ve done full-auto fire while I was in the Air Force with an M16A2, M4 carbine, M14, M60, M249, and an AK47. The M16 and M4 were all over the place; the M14 and AK were pretty steady but still jumping around and hard to control and not very accurate; the M60 and M249 were both the most stable and most accurate firing on full-auto. Guess what? The M4 and M16A2 were the lightest; M14 and AK47 heavier, M60 and M249 heavier still. It’s why I was trained for short, controlled bursts with the M4 and M16 but was trained that longer burst suppressive fire was doable with the M14 and obviously the M60 and M249 - sustained autofire in the M60 can result in barrel droop due to heat and drive down accuracy, but it can sustain 100-200 round sustained fire without too many problems and a higher level of accuracy than anything else.
[QUOTE=Balthisar]
Having looked at the firing mechanisms of both, it astounds me that there aren’t a lot of street modified automatic weapons. It’s trivial to adapt the M2 to fully automatic. I seem to recall that I believed I’d be able to convert the semi-automatic to full automatic, and leave the three round burst alone as the simplest option.
[/QUOTE]
Ever looked at a civilian AR-15? They don’t have an auto sear, which is the main thing you need to get full auto fire. The lower receiver is milled differently, the bolt carrier, disconnector, and I think some other parts are different as well. It appears trivial to convert an M16-A2 to full auto because it’s already got everything you need - it’s just that the full auto disconnector was modified to stop firing after 3 rounds. Taking a civilian version that’s never had full auto capability and converting it to full auto is a different matter altogether.
Anecdote is not data, I know, but I’ll give you this:
I took my girlfriend and a buddy to the Gun Store in Las Vegas a long time ago, the place that famously rents full auto guns to people coming in off the streets. I’ve got loads (haha) of firearm experience, at the time neither my girlfriend or my buddy had ever fired a gun.
I chose the AK (in .223), she chose the MP5, and my buddy went with the Uzi. The muzzle jump on the AK was noticeable but easily controllable by someone who’s used to it. I could put a full clip “on target” if I started firing at the thighs. By the time I blew off 30, I’d be at the head. The MP5 had, as far as I could tell, almost no appreciable muzzle rise at all. A full clip of 9mm coming out of that was on center mass no problem, even in the hands of a pure noob. The Uzi (also in 9mm) OTOH was the equivalent of holding an angry badger by the genitals. After a quick burst it was aiming at the angels. A sustained burst would have put holes in the roof of the range. A clip dump would have ended up with all of us being shot. 
I attributed the performance to both the weight of the weapon itself and length of the bolt cycle. The longer and heavier the bolt, the more of that pressure that was being used to cycle the weapon. The Uzi, weighing near nothing and having a bolt cycle distance of about two inches was effected much more than the other two weapons.
Here’s an anecdote:
When I was in Navy ROTC, I participated in a summer training exercise once with the Marines. I had an M-16A2 (selectable single shot/three-round burst) and 30-round magazines (with blanks, of course).
We were supposed to ambush another column of midshipman coming down a trail in the middle of the night. The signal to fire would be a flash grenade going off. They knew we were out there, so they moved as quietly as possible. It was pitch dark, and nobody had night-vision equipment.
After about an hour of waiting, I heard a slight noise from the trail, and as I was trying to decide if anyone was there or not, the grenade went off. Even in 3-round burst mode, I emptied my 30-round magazine in about 2-3 seconds. I remember trying to figure out what was wrong with my weapon, because I had no recollection of pulling the trigger 10 times. :dubious:
Another factor in the ‘shooting ducks’ phenomena: in a defensive position you are stationed behind a berm of some sort. If you are attacked, it will probably on be on a moonless night. You can’t see diddley squat as it is. If the enemy is as competent as the VC, they will have carefully observed your defense, and perhaps probed it to look for gaps in your defensive fire. They know that in the dark, without any reference points, you will have a tendency to fire high because you don’t want any ricochet back at you. If you do hit anything, (like a psp runway), the resulting ricochet sparks will be mistaken for enemy fire, drawing even more of your fire.
(Try it some moonless night. Go out in the woods where there is no artificial light. Climb about halfway up a hill and see if you can see the bottom of the hill you are on let alone someone low crawling up toward you. They don’t have to woory about noise, because you are making enough racket to cover an elephant.)
Meanwhile, the enemy is going to try to penetrate your defense through the gaps in your defensive fire, certainly not through your automatic weapons fire. The idea is to get a few men through your perimeter, causing you to start shooting within the perimeter and causing chaos as you start shooting each other.
This tactic by the VC resulted in numerous war stories about a base camp getting ‘overrun’ with very few VC casualties.
I tried to train my men to maintain fire discipline at all times. Listen for commands and don’t fire unless instructed. (Only 4 men manning a GR point attached to a base company). Fortunately, thery were only attacked once if at all, and even more fortunately, I wasn’t there at the time.
[QUOTE=GomiBoy]
ALL automatic fire makes the weapon jump and jerk and raise up; the longer you auto-fire and the lighter the weapon the stronger this force is. “Shooting ducks” is an exaggeration, but the fact remains - autofire with an assault rifle is hugely inaccurate. I would only think it was useful in a very very small number of circumstances, and only as a last resort. It’s contrary to most small-arms combat training anymore, and largely a thing for movies and video games. Your video shows guys fucking around in the field, not on combat maneuvers. It’s just dumb to autofire with an M4 in any normal combat situation.
I’ve done full-auto fire while I was in the Air Force with an M16A2, M4 carbine, M14, M60, M249, and an AK47. The M16 and M4 were all over the place; the M14 and AK were pretty steady but still jumping around and hard to control and not very accurate; the M60 and M249 were both the most stable and most accurate firing on full-auto. Guess what? The M4 and M16A2 were the lightest; M14 and AK47 heavier, M60 and M249 heavier still. It’s why I was trained for short, controlled bursts with the M4 and M16 but was trained that longer burst suppressive fire was doable with the M14 and obviously the M60 and M249 - sustained autofire in the M60 can result in barrel droop due to heat and drive down accuracy, but it can sustain 100-200 round sustained fire without too many problems and a higher level of accuracy than anything else.
[/QUOTE]
And this is where I gather video games have it wrong. In games like counterstrike, the M4 is on the dot for the first 2-3 shots and then slowly works up into a pizza slice range, while the AK47 is dead on for the first shot and then is all over the place, and the M249 is just all over the place. This is because in the context of the game, the M4 is supposed to be the “BOOM headshot” weapon, and the heavier “stronger” guns are meant to be the body shot weapons (more or less). So that’s pretty much my area of expertise, video games ( ) and I guess I won’t be adding too much to the discussion by stating that yes, even in video games controlled bursts of 2-3 shots are best almost all the time. If you turn a corner and find yourself in front of 3 baddies, ok try your luck and unload everything. But as long as you can keep your cool, short bursts aimed at the neck/head is how you win that LAN game bet for some beer and a pizza.
[QUOTE=Cluricaun]
Anecdote is not data, I know, but I’ll give you this:
I took my girlfriend and a buddy to the Gun Store in Las Vegas a long time ago, the place that famously rents full auto guns to people coming in off the streets. I’ve got loads (haha) of firearm experience, at the time neither my girlfriend or my buddy had ever fired a gun.
I chose the AK (in .223), she chose the MP5, and my buddy went with the Uzi. The muzzle jump on the AK was noticeable but easily controllable by someone who’s used to it. I could put a full clip “on target” if I started firing at the thighs. By the time I blew off 30, I’d be at the head. The MP5 had, as far as I could tell, almost no appreciable muzzle rise at all. A full clip of 9mm coming out of that was on center mass no problem, even in the hands of a pure noob. The Uzi (also in 9mm) OTOH was the equivalent of holding an angry badger by the genitals. After a quick burst it was aiming at the angels. A sustained burst would have put holes in the roof of the range. A clip dump would have ended up with all of us being shot.
I attributed the performance to both the weight of the weapon itself and length of the bolt cycle. The longer and heavier the bolt, the more of that pressure that was being used to cycle the weapon. The Uzi, weighing near nothing and having a bolt cycle distance of about two inches was effected much more than the other two weapons.
[/QUOTE]
The AK and the MP5 are both locked-breech weapons that fire from a closed bolt. The UZI is blowback and fires from an open bolt. Briefly, this means that the UZI has a much heavier bolt slamming back and forth as the weapon cycles. Also, pulling the trigger even for single shots means having that heavy bolt slam forward to strip a cartridge from the magazine. This is the major reason it is much less controllable and accurate than the MP5. OTOH, open-bolt firing weapons are widely considered to be less prone to overheating.
[QUOTE=Tristan]
I am amused by the progression of slang though… from whatever was used in the 70’s, we now have a “Last Starfighter” reference. Awesome!
[/QUOTE]
Heh, I’m surprised at a line from a film like that being used by the military as slang
Good info so far on the Uzi vs MP5 recoil but I always considered it to be more of a center of gravity thing. The Uzi’s center of gravity is probably right where your hand is, and the bullets are fired an inch or two higher, making the recoil tilt the gun backwards pretty easily. The MP5 COG is probably forward of the hand and the gun has a lot more weight forward of the COG. It seems to me that the design of the Uzi would make the recoil get a lot more leverage on the gun than other guns like the MP5.
You’re right about the center of gravity contributing to muzzle rise. The thing about open bolt weapons like the UZI, Sten, Thompson, and most other SMG’s is that, in contrast to the closed bolt MP5, the heavy bolt slamming forward jars the gun even before the cartridge goes off. This contributes to lackluster accuracy even when fired in semi-automatic mode. In a closed bolt gun, all that moves initially is a hammer or a striker; there’s not nearly as much mass moving around to take the gun off target. That mass also comes into play during full auto fire as I referenced in my earlier post.
[QUOTE=Mojo Pin]
And this is where I gather video games have it wrong.
[/QUOTE]
The games are not wrong. The 5.56mm M-16 / M-4 are dead-on for the first 2-3 rounds then rapidly going out of control, so that is why the ‘burst’ function was developed for them - recoil is very much cumulative. The 5.56mm round is very light and you can also carry a lot more magazines, and the round is designed to tumble on contact causing much more soft tissue damage and increasing the stopping power (in civilian usage, the 5.56mm is the same as a .223 caliber; it’s usually considered a ‘varmint’ round for small game hunting at medium range). The M249 Squad Automatic Weapon, which also uses the 5.56mm round, is designed from the ground up as a lighter version of the M-60 and to be used for suppressive fire. It’s just a more portable version of the M-60 Light Machine Gun and can carry more ammo because of lighter weight rounds.
But the M-14’s tactical use is quite different. The heavier 7.62mm round in the M-14 (and M-60) have more recoil; the weapon is quite a bit heavier which adds some stability (although the design of the M-14 is inherently unstable under autofire), and 7.62mm rounds give better range, better penetration, and better stopping power than the 5.56mm. The M-14 is usually used as a sniper team back up weapon, as well as a special operations primary weapon, where it is almost never used on full-auto except in direst emergency. The M-14 uses the same caliber round as the US military sniper rifle (M24), so one ammo source for both weapons and the 2-man sniper team can deploy more lightly. And on single shot, the M-14 is effectively one-shot, one-kill so conservative use of the weapon is much more efficient which is what SOF and sniper teams want. The M-14 was basically a kludged M-1 with full auto capability, and has some serious design flaws reflecting this.
Finally, the M-60 is not designed, intended, or used for accurate shooting, more for hosing down an area where you think the bad guys might be with suppressive fire.
As for Warsaw Pact weapons - the AK comes in two variants, 47 and 74. The 47 fires a similar round to the M-14 and M60 (7.62mm x 39) with similar characteristics, but the 47 was always designed first and foremost to be durable and usable in all conditions by less-trained troops; the AK will just keep working almost no matter what and it hardly ever jams. I’ve seen demos where an AK47 was thrown into an icy mud puddle, left there overnight, pulled out the next day and fired through a full mag. But it’s not really designed as an accurate weapon, and Soviet / Chinese field tactics were much more about using mass of troops and combined assaults to achieve their purpose (i.e. attacking with infantry, tanks, artillery, and aircraft all at the same time) rather than accurate small-arms fire and small unit tactics. The AK74 is an upgraded AK47, using a 5.45mm round, but with the same look and feel as the AK47 and much of the same design philosophy. The 74’s round is quite a bit lighter (much like the NATO 5.56mm round) and it’s use is similar to the M-16 series - a standard light infantry weapon, with the lighter round allowing for much more ammo to be carried per trooper. But again, the sacrifice made for such reliability is accuracy - the mass-produced AK series are renowned for not being the most accurate of weapons, largely due to the lack of precision machining in the build process. But it is incredibly reliable.
One further note - all military small-arms training that I’ve ever heard of is to go for center mass, regardless of weapon used (yes, even for snipers), but with an M-60 or M-249, the whole idea is to target an area rather than an individual. I don’t know how much this has changed with the advent of body armor, or if the military really worries about body armor on it’s opponents just yet (seems not to be too many body-armored insurgents in Iraq, for instance), but I was always trained to go for center mass and my brother, who was a Marine Corps and later Army National Guard scout sniper was too.
Scumpup - center of gravity definitely effects accuracy of autofire for rifles as well. That’s why the M-16 design by Eugene Stoner aligned the butt stock of the M-16 with the barrel and then put on a hand grip. The M-14’s center of gravity causes it to pivot around the hand grip when fired, thus pulling the barrel off target. Further re-designs of the M14 have included a hand grip and re-aligned the butt stock along the barrel to reduce this, but it is still a problem and part of the reason why the M-14 isn’t used as the standard infantry weapon. Center of gravity is also why the Mac-10 had a little strap attached in front of the pistol grip - you hold the strap with your other hand and it helps control the weapons kick-up when firing full-auto.
Negative.
7.62 x 39mm 123 grain bullet at 2300 feet per second.
7.62 x 51mm 146 grain bullet at 2472 feet per second.
The 7.62 x 51mm is nearly twice as powerful in terms of muzzle energy (1.7x). It also has a flatter trajectory, is much more penetrative, and has a much, much greater effective range. All this is, of course, at the cost of greater cartridge weight and greater recoil.
The 7.62 x 51mm is a full sized rifle cartridge; it duplicates the ballistics of the .30-06 as used in the M-1 Garand. The 7.62 X 39mm is an intermediate or “assault rifle” cartridge; cartridges in this family were designed to have reduced recoil and weight at the expense of range and power.