# Why do squad automatic weapons (light machine guns) have long barrels? **URL:** \ **Category:** Factual Questions\ **Created:** [November 24, 2001, 1:54am UTC](https://boards.straightdope.com/t/why-do-squad-automatic-weapons-light-machine-guns-have-long-barrels/94976 "2001-11-24T01:54:37Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![SenorBeef](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senorbeef/32/2220_2.png) [@SenorBeef](https://boards.straightdope.com/u/SenorBeef)\ **Post date:** [November 24, 2001, 1:54am UTC](https://boards.straightdope.com/t/why-do-squad-automatic-weapons-light-machine-guns-have-long-barrels/94976/1 "2001-11-24T01:54:37Z")
Specifically, I’m asking why LMGs tend have longer barrels than their rifle counterparts. Ex: M249 Saw has a 22" (I think) barrel compared to an m16 at 18", and a russian RPK has a 20" barrel compared to a 16.5" AKM. Adding barrel length is usually to increase accuracy on cartridges can benefit from it - however, in a squad automatic weapon, accuracy really isn’t all that critical, and the accuracy a 18" or 16.5" barrel could provide respectively is adequate. So what’s the point? Just a simple way to add more weight for stability, or what? ---
**Author:** ![Triskadecamus](https://avatars.discourse-cdn.com/v4/letter/t/b19c9b/32.png) [@Triskadecamus](https://boards.straightdope.com/u/Triskadecamus)\ **Post date:** [November 24, 2001, 2:19am UTC](https://boards.straightdope.com/t/why-do-squad-automatic-weapons-light-machine-guns-have-long-barrels/94976/2 "2001-11-24T02:19:46Z")
Longer barrels on rifles improve accuracy, and increase range, as well. The loss of control from full automatic fire is potentially very large, and the reduction of that loss is worth the extra weight in what is primarily used as an emplacement arm, rather than as assault weapon. With a pair of SAWs a light infantry squad can control a fairly large field of fire out to an extreme range, while providing close protection with riflemen deployed around the SAW emplacements. Longer barrels are generally more massive as well, and are able to sustain longer periods of rapid fire without deformation from heat. That increases the effective firepower over time. It is a movie myth that SAW fire is always a long full automatic burst. Three round to five round bursts are far more useful in a military sense. (Not to mention the usefulness of not humping half a million rounds of ammo out into the boonies.) If you are going to be using it as a distance weapon, you want to tighten up the strike pattern of your five round bursts as much as possible. ## Tris “For there has never been a protracted war from which a country has benefited.” ~ Sun-tzu ~ ---
**Author:** ![SenorBeef](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senorbeef/32/2220_2.png) [@SenorBeef](https://boards.straightdope.com/u/SenorBeef)\ **Post date:** [November 24, 2001, 2:53am UTC](https://boards.straightdope.com/t/why-do-squad-automatic-weapons-light-machine-guns-have-long-barrels/94976/3 "2001-11-24T02:53:18Z")
Sounds good enough. Thanks. ---
**Author:** ![Barking\_Spider](https://avatars.discourse-cdn.com/v4/letter/b/9dc877/32.png) [@Barking\_Spider](https://boards.straightdope.com/u/Barking_Spider)\ **Post date:** [November 24, 2001, 3:11am UTC](https://boards.straightdope.com/t/why-do-squad-automatic-weapons-light-machine-guns-have-long-barrels/94976/4 "2001-11-24T03:11:12Z")
Actually, M16s have 20 inch barrels. However, the newest version of the M16, the M4, has a 16 inch barrel. ---
**Author:** ![Gunslinger](https://avatars.discourse-cdn.com/v4/letter/g/4491bb/32.png) [@Gunslinger](https://boards.straightdope.com/u/Gunslinger)\ **Post date:** [November 24, 2001, 3:22am UTC](https://boards.straightdope.com/t/why-do-squad-automatic-weapons-light-machine-guns-have-long-barrels/94976/5 "2001-11-24T03:22:46Z")
> [@](#): > > \*Originally posted by Barking Spider \* > \*\*Actually, M16s have 20 inch barrels. However, the newest version of the M16, the M4, has a 16 inch barrel. \*\* The M4 is the extra-short Special Forces version. Short barrel, telescoping stock…some even have real “rock & roll” mode instead of just the 3-round burst of the standard M16 that the vast majority of the military gets. ---
**Author:** ![astro](https://avatars.discourse-cdn.com/v4/letter/a/9dc877/32.png) [@astro](https://boards.straightdope.com/u/astro)\ **Post date:** [November 24, 2001, 4:47am UTC](https://boards.straightdope.com/t/why-do-squad-automatic-weapons-light-machine-guns-have-long-barrels/94976/6 "2001-11-24T04:47:51Z")
> [@](#): > > \*Originally posted by Gunslinger \* > \*\* > > > [@](#): > > > > \*Originally posted by Barking Spider \* > > \*\*Actually, M16s have 20 inch barrels. However, the newest version of the M16, the M4, has a 16 inch barrel. \*\* > > …some even have real “rock & roll” mode instead of just the 3-round burst of the standard M16 that the vast majority of the military gets. \*\* I’m assuming this doesn’t mean their weapons start playing Buddy Holly tunes as the squad advances over the hill. What does this mean? Fully automatic fire? ---
**Author:** ![Alessan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alessan/32/465_2.png) [@Alessan](https://boards.straightdope.com/u/Alessan)\ **Post date:** [November 24, 2001, 5:06am UTC](https://boards.straightdope.com/t/why-do-squad-automatic-weapons-light-machine-guns-have-long-barrels/94976/7 "2001-11-24T05:06:24Z")
**Trisk** has it right. Back when my Lietenant gave me my first FN-MAG, he told me to remember that outside of the sniper, I had the most accurate, longest-ranged weapon in the platoon. He also made sure I knew to only fire in short bursts - after enough training, my trigger finger was so good that I could control exactly how many bullets would leave the barrel with every pull (I was very good at firing single-shot - no mean feat with an automatic-only weapon). FTR, I don’t think I ever fired more than 6-7 rounds in one burst. ---
**Author:** ![Gunslinger](https://avatars.discourse-cdn.com/v4/letter/g/4491bb/32.png) [@Gunslinger](https://boards.straightdope.com/u/Gunslinger)\ **Post date:** [November 24, 2001, 5:29am UTC](https://boards.straightdope.com/t/why-do-squad-automatic-weapons-light-machine-guns-have-long-barrels/94976/8 "2001-11-24T05:29:58Z")
> [@](#): > > \*Originally posted by astro \* > \*\*What does this mean? Fully automatic fire? \*\* Yes. ---
**Author:** ![SenorBeef](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senorbeef/32/2220_2.png) [@SenorBeef](https://boards.straightdope.com/u/SenorBeef)\ **Post date:** [November 24, 2001, 8:02am UTC](https://boards.straightdope.com/t/why-do-squad-automatic-weapons-light-machine-guns-have-long-barrels/94976/9 "2001-11-24T08:02:13Z")
> [@](#): > > \*Originally posted by Gunslinger \* > \*\* > > > [@](#): > > > > \*Originally posted by Barking Spider \* > > \*\*Actually, M16s have 20 inch barrels. However, the newest version of the M16, the M4, has a 16 inch barrel. \*\* > > The M4 is the extra-short Special Forces version. Short barrel, telescoping stock…some even have real “rock & roll” mode instead of just the 3-round burst of the standard M16 that the vast majority of the military gets. \*\* Actually, no. It’s not really “extra short”, because we still use car-15s with 11" barrels for special ops. And it’s not just a special ops things - lots of line units are getting issued M4s, especially those expected for urban type settings. And the M4A1, by far, the most common variant, is safe, single, full. (I’m glad they got around to correcting this, erm, mistake on the m16. The m16a3 and a4 both have that setup too, I think.) ---
**Author:** ![DPWhite](https://avatars.discourse-cdn.com/v4/letter/d/d26b3c/32.png) [@DPWhite](https://boards.straightdope.com/u/DPWhite)\ **Post date:** [November 24, 2001, 8:17am UTC](https://boards.straightdope.com/t/why-do-squad-automatic-weapons-light-machine-guns-have-long-barrels/94976/10 "2001-11-24T08:17:18Z")
Short hijack here, what is the infantry using for sniping these days? I thought the M4 was a carbine, smaller and lighter than the M16, but same ammo, am I misinformed? ---
**Author:** ![Vic\_Ferrari](https://avatars.discourse-cdn.com/v4/letter/v/dbc845/32.png) [@Vic\_Ferrari](https://boards.straightdope.com/u/Vic_Ferrari)\ **Post date:** [November 24, 2001, 9:16am UTC](https://boards.straightdope.com/t/why-do-squad-automatic-weapons-light-machine-guns-have-long-barrels/94976/11 "2001-11-24T09:16:31Z")
> [@](#): > > \*\*And the M4A1, by far, the most common variant, is safe, single, full. (I’m glad they got around to correcting this, erm, mistake on the m16. The m16a3 and a4 both have that setup too, I think.) \*\* According to this page: [http://shoga.wwa.com/~dvelleux/m16rifle.html#DEVEL](http://shoga.wwa.com/~dvelleux/m16rifle.html#DEVEL) the A3 is full auto while the A4 is three round burst. I can vouch for the A3, it’s definitely full auto. I don’t think I’ve ever seen an A4 though. I personally find it insulting to issue some of our troops weapons that will only do the three round burst. If you don’t trust your guys you shouldn’t be handing them guns in the first place. ---
**Author:** ![Doc\_Nickel](https://avatars.discourse-cdn.com/v4/letter/d/5fc32e/32.png) [@Doc\_Nickel](https://boards.straightdope.com/u/Doc_Nickel)\ **Post date:** [November 24, 2001, 11:45am UTC](https://boards.straightdope.com/t/why-do-squad-automatic-weapons-light-machine-guns-have-long-barrels/94976/12 "2001-11-24T11:45:35Z")
Vic- I don’t think its a “trust” thing, rather, I’m almost certain it’s training to maximize soldier effectiveness. In other words, in the event the SHTF for real, one does not want a soldier to panic and simply hold down the trigger thinking all the bad guys will fall down or go away a’la Rambo. Doing so is a great way to waste ammo with little gain, and a grunt can only carry so much. To counter this to some extent, the soldiers are trained specifically to keep auto bursts to three or less, forcing him to pause a little and hopefully aim. Removing the potential for full-auto from the gun simply assures there’s no accidental or intentional rock-and-roll even during training, and if they’re not going to teach it anyway, why bother having it? ---
**Author:** ![August\_West](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/august_west/32/18069_2.png) [@August\_West](https://boards.straightdope.com/u/August_West)\ **Post date:** [November 24, 2001, 1:57pm UTC](https://boards.straightdope.com/t/why-do-squad-automatic-weapons-light-machine-guns-have-long-barrels/94976/13 "2001-11-24T13:57:15Z")
That’s why it pays to be in the reserves! You get the “old and outdated” stuff. That means the weapons in my unit are M16A1’s, with “full rock and roll mode”. Every year when we qualify somehow extra ammo is accidentally ordered, and it’s such a pain to return ammo to the armory. 😉 ---
**Author:** ![Vic\_Ferrari](https://avatars.discourse-cdn.com/v4/letter/v/dbc845/32.png) [@Vic\_Ferrari](https://boards.straightdope.com/u/Vic_Ferrari)\ **Post date:** [November 24, 2001, 7:03pm UTC](https://boards.straightdope.com/t/why-do-squad-automatic-weapons-light-machine-guns-have-long-barrels/94976/14 "2001-11-24T19:03:35Z")
Hey Doc - Your explanation is still an issue of trust though, don’t you think? They’re are taking away some of the flexibility of the weapon because they don’t trust their troops to exercise fire discipline. ---
**Author:** ![SenorBeef](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senorbeef/32/2220_2.png) [@SenorBeef](https://boards.straightdope.com/u/SenorBeef)\ **Post date:** [November 25, 2001, 12:10am UTC](https://boards.straightdope.com/t/why-do-squad-automatic-weapons-light-machine-guns-have-long-barrels/94976/15 "2001-11-25T00:10:29Z")
> [@](#): > > \*Originally posted by DPWhite \* > \*\*Short hijack here, what is the infantry using for sniping these days? > > I thought the M4 was a carbine, smaller and lighter than the M16, but same ammo, am I misinformed? \*\* No, that’s right. I was contending that it was a “special ops” weapon, since it’s replacing m16s (and other stuff) in lots of regular units. ---
**Author:** ![SenorBeef](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senorbeef/32/2220_2.png) [@SenorBeef](https://boards.straightdope.com/u/SenorBeef)\ **Post date:** [November 25, 2001, 12:12am UTC](https://boards.straightdope.com/t/why-do-squad-automatic-weapons-light-machine-guns-have-long-barrels/94976/16 "2001-11-25T00:12:37Z")
> [@](#): > > \*Originally posted by Vic Ferrari \* > \*\*Hey Doc - Your explanation is still an issue of trust though, don’t you think? They’re are taking away some of the flexibility of the weapon because they don’t trust their troops to exercise fire discipline. \*\* Yes, you’re correct. Three round burst limiters are a way to compensate for insufficient training, nothing more. All you’re doing is adding mechanical complexity (and mechanical failure) to a rifle that could do the exact same burst with full auto and a skilled rifleman. In addition, for the m16, the burst device is rather shitty (compared to say, H&K)… if you fire 2 rounds on burst mode, the next trigger pull gives you one shot. I’m sure that’s annoying. ---
**Author:** ![Alessan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alessan/32/465_2.png) [@Alessan](https://boards.straightdope.com/u/Alessan)\ **Post date:** [November 25, 2001, 1:08am UTC](https://boards.straightdope.com/t/why-do-squad-automatic-weapons-light-machine-guns-have-long-barrels/94976/17 "2001-11-25T01:08:38Z")
> [@](#): > > \*Originally posted by SenorBeef \* > \*\* > No, that’s right. I was contending that it was a “special ops” weapon, since it’s replacing m16s (and other stuff) in lots of regular units. \*\* Oddly enough, the Israeli Army recently announced that it was planning to equipt _all_ of its infantry - special or not - with M-4s by the end of next year, replacing the CAR-15s they’re currently equipt with. ---
**Author:** ![Monster104](https://avatars.discourse-cdn.com/v4/letter/m/c6cbf5/32.png) [@Monster104](https://boards.straightdope.com/u/Monster104)\ **Post date:** [November 25, 2001, 4:18am UTC](https://boards.straightdope.com/t/why-do-squad-automatic-weapons-light-machine-guns-have-long-barrels/94976/18 "2001-11-25T04:18:00Z")
> [@](#): > > Yes, you’re correct. Three round burst limiters are a way to compensate for insufficient training, nothing more. No, this _isn’t_ correct. If you’ve ever noticed, automatic weapons have VERY powerful kicks. Any more than 3 bursts can throw the aim completely off-target, resulting in a blatant waste of resources. On a battlefield, ammo is scarce, and they can’t _afford_ waste. ---
**Author:** ![Monster104](https://avatars.discourse-cdn.com/v4/letter/m/c6cbf5/32.png) [@Monster104](https://boards.straightdope.com/u/Monster104)\ **Post date:** [November 25, 2001, 4:19am UTC](https://boards.straightdope.com/t/why-do-squad-automatic-weapons-light-machine-guns-have-long-barrels/94976/19 "2001-11-25T04:19:32Z")
Dammit, one more thing to add to my post: The limiters are to prevent any kind of outside interference from causing an accidental automatic discharge. ---
**Author:** ![SenorBeef](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senorbeef/32/2220_2.png) [@SenorBeef](https://boards.straightdope.com/u/SenorBeef)\ **Post date:** [November 25, 2001, 4:53am UTC](https://boards.straightdope.com/t/why-do-squad-automatic-weapons-light-machine-guns-have-long-barrels/94976/20 "2001-11-25T04:53:27Z")
> [@](#): > > \*Originally posted by Monster104 \* > \*\* > > > [@](#): > > > > Yes, you’re correct. Three round burst limiters are a way to compensate for insufficient training, nothing more. > > No, this _isn’t_ correct. If you’ve ever noticed, automatic weapons have VERY powerful kicks. Any more than 3 bursts can throw the aim completely off-target, resulting in a blatant waste of resources. On a battlefield, ammo is scarce, and they can’t _afford_ waste. \*\* In most cases, yes, more than 3 rounds is a waste. You don’t need a limiter in order to fire 3 rounds at a time. You need training. The US doesn’t have enough confidence in it’s infantry training to allow them to trust the skill of their soldiers to handle their weapons with proper fire discipline. Hence they put an artificial limiter on there. I’ll stand by this. Unless it’s some special burst mode (ie the g36 or something), burst limiters do nothing that a full auto weapon cannot. And they add unnecesary mechanical failure to the rifle. [Next page](https://boards.straightdope.com/t/why-do-squad-automatic-weapons-light-machine-guns-have-long-barrels/94976.md?page=2)