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Burning Out Machine Gun Barrels

Discussion in 'Small Arms and Edged Weapons' started by superbee, May 15, 2013.

  1. TiredOldSoldier

    TiredOldSoldier Ace

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    Just to complete the picture does anyone know how much does a German 250 round ammo box weight?

    BTW I apparently got a couple of things wrong in my calculations, while the generic formula still looks sound the MG 42 usually used a 50 round belt not a 60 rounds one, though a 250 one also existed and suggested barrel change was at 250 rounds not 180. The end result doesn't change much though.
     
  2. USMCPrice

    USMCPrice Idiot at Large

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    Actually it's the 7.62 x 51mm NATO or just 7.62 NATO. The round is similar ballistically to the 30-06, and you are correct it is due to more modern powder. As for comparing the 7.62 NATO or 30-06 to the 7.92 x 57 Mauser, they look to have similar performance, but if you go out to a lot of ammo websites you'll see heated debates about which is superior. I think that most of those advocating for the 7.92 Mauser are pretty much just German fanboys, based upon their arguments. Conversely, a good many advocating the 30-06 believe anything made in "Merica" is superior. I don't personally think there's enough of a difference to have much of an effect across the full spectrum of the rounds employment. I do agree with you that useable effective ranges in combat would probably be similar, with the skill of the individual gunner being the biggest determinate of how effective the gun was employed, and at what ranges.

    I think KodiacBeer would probably be the most knowledgeable on the ballistic comparison of the rounds. Maybe we'll be lucky and have him add his two cents.
     
  3. KodiakBeer

    KodiakBeer Member

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    I agree with your input. To put them in civilian terms, the .308, 30.06 and 8mm Mauser are close enough in performance that the differences are negligible. The heavier 8mm round had slightly greater energy at long range, but I don't think anyone hit at 1000 yards would know the difference.
     
  4. Poppy

    Poppy grasshopper

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    Ten second barrel change sounds fast in battle. Those are F-1 numbers...

    USMCP should write a book. Really enjoyed that. Even sell a bit to Guns and Ammo. I'd buy that.

    Sustained rate: Actual rate of fire that a weapon can continue to deliver for an indefinite length of time without seriously overheating. (Army) - Or without doing other mechanical damage to the weapon or weapon system. (See also maximum rate of fire.)

    I did not know the definition.

    Is it possible to adjust a machine gun to fire at 100 rpm, or is that 3 round burst setting, or single shot?
    Severloh must have had a sore trigger finger. (not making light of a serious thingy)
     
  5. CAC

    CAC Ace of Spades

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    Might be possible to jimmy it...the SLR could be with a match stick, to make it full auto... : )
     
  6. KodiakBeer

    KodiakBeer Member

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    The BAR could be adjusted to shoot as low as 250 rounds per minute. There would be little point in going much slower than that since it could just be fired semi-auto.

    I wonder how few rounds a trained gunner could get off with an MG42. I doubt even the best gunner could get off a single shot, but maybe a quick 3 or 5 round burst?
     
  7. phylo_roadking

    phylo_roadking Member

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    Ofhhand I know of one example, albeit an early one - the Lee-Metford in the Boer War had a tendancy to very rapid wear of the edges of the three groves in the barrel - which is why the Lee Enfield saw the change to six grooves IIRC...

    But then the Lee Enfield, with its change to cordite propellant, saw corrosion of the edges of the lands unless regularly cleaned and ASAP after use...

    Sometimes you just can't win...
     
  8. USMCPrice

    USMCPrice Idiot at Large

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    You don't adjust the gun (in most cases), the gunner controls the rate of fire by the number of rounds in the burst and the pause between bursts. We trained our gunners to try for 3-5 and 6-9 round bursts. That's why you fire so much in training, so you learn to fire 3-5 rounds or 6-9 habitually without thinking, you do it automatically. Same-same with the pause, you learn a rhythm, you don't actually sit there and count 1000, 2000. (though you do an actual physical count when jumping; head down, chin tucked into chest, 1000, 2000,3000,4000,5000, head back, look up, check canopy. Sometimes you don't feel the opening shock, when you do you immediately go to head back, look up, check canopy). The math: Using a gun with a cyclic rate of 600 rounds per minute you'd fire a 5 round burst in 1/2 second. Pause 2.5 seconds and fire another burst. A total of 3 seconds per cycle. 60 seconds in a minute /3=20 cycles x 5 rounds per burst=100 rounds per minute. Due to the 2.5 second pauses you're actually allowing the barrel to cool about 50 seconds out of every minute. Same with rapid rate, 1/2 second burst, 1 second pause, 1.5 seconds per cycle. 60/1.5=40, 40 x 5 rounds per burst=200 rounds per minute.
    Guns are optimally employed in pairs (because of the cross-fire), you spend a lot of training time teaching your gunners to get their guns to "talk" to one another. Gun one speaks, slight pause, gun two speaks, slight pause, gun one speaks, repeat. This uses the same rhythm and reinforces it in the gunners subconcious. On the defensive using the tripod and T & E mechanism you can pre-register targets as to range and azimuth, record it and dial the dope in when engaging a target in that area, making it easier and quicker to get on target. Which brings us to aiming, normal prceedure is to use the sights to get in the approximate area of the target and then visually walk you tracers or bullet splashes onto the target. Example: I have a vehicle in the open at approximately 800 meters, I flip my sights up, calibrate to 800 meters, aim at the target and fire a burst, observe the tracers/bullet splashes, flip the sights down and adjust onto the target by guesstimation, a good gunner will be all over the target by the second or third burst. Your A-gunner (or the machine gun squad leader) helps here by observing the strike of the rounds and calling out corrections, i.e. left 25, up 50.
    While I have spent a lot of time on the different types of fire, it's just theoretical. When doing it for real you take the principles you have learned and apply them to your real world situation. same vehicle as above, I sight, fire a five round burst, my tracer/bullet strikes are short and to the right, my A-gunner calls out a correction of let 25, up 50. I adjust slightly, fire a 5 round burst, on target, I fire a 10-12 round burst centering my cone of fire on the center of the target, (cone of fire is more important here than beaten zone because the target is vertical). I'll pause long enough to observe the strike of my rounds and effect on target and fire another 10-12 round burst if necessary, and repeat or even fire a longer burst if necessary until the target is neutralized. I'm not really using either the sustained or rapid rate of fire but using the number of rounds in my burst to optimize my effectiveness and preserve my ammo supply to the greatest extent. There is no reason to fire 12 round bursts when trying to acquire the target, once on target 12 rounds gives me a better chance to neutralize it in one burst. There's enemy infantry behind a berm, I want to suppress them to allow a fire team to maneuver around to their flank to engage them. I'd use 3-5 round bursts to keep them pinned and minimize their ability to return fire while the fire team moves, using 6-12 round bursts when I'm unlikely to inflict casualties is inefficient. Because it's crucial for me to keep them pinned I may only pause a second and a half between bursts, using the pause to traverse randomly right and left between bursts, do not establish a pattern that the enemy can exploit. If I were traversing uniformly in one direction or the other, the enemy could pick up on it and either move or fire from the end of their position away from my direction of traverse. Because my cycle would be approximately 2 seconds (1/2 second for burst, one and a half seconds for pause) my rate of fire would be around 150 rounds per minute. Normally when using sustained rate you have to change the barrel every 10 minutes, with sustained rate every two minutes, so I probably can keep the target suppressed at this rate for 3-4 minutes before I have to change barrels and will have burned through 450-600 rounds.

    Hope this gives you a little better picture.
     
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  9. CAC

    CAC Ace of Spades

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    Nicely explained...again Vietnam footage...you can hear that rhythm perfectly...thanks USMC Price : ) Insite is a wonderful thing to share...
     
  10. USMCPrice

    USMCPrice Idiot at Large

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    Thank you for the comment, CAC. Didn't think about film/video. Here's an older video of machine gunners training on Okinawa, using the .50 cal Browning. The M2 Browning has a sustained/slow rate of 40 rounds per minute using 5-7 round bursts with 10-15 second pauses. Remember these guys are learning. Gun two (right side) is having a problem keeping his bursts in the 5-7 round range and several times talks over the #1 gun because of this. The instructor has them trying to fire sustained fire, #1 gun is pretty good at keeping his bursts regular and in the 5-7 round range and is generally keeping a rhythm of about 3 seconds between bursts, later in the video he calms down and his pauses stretch out to about 5 seconds at one point, then he loses focus and starts responding to the number 2 gun and his pauses drop back to about 3 seconds. Notice also that at one point the number 2 gun runs dry on ammo, while number 1 gun continues to fire. They draw identical round counts, so this is due to #2 gun firing longer bursts several times. The instructors are trying to get them used to the 5-7 round bursts and working in concert with a second gun, once they achieve this they'll work on their pause length and rhythm. Nervous, inexperienced gunners have a tendency to speed up their tempo when working with another gun. You'll be able to discern when they get close to having it right.
    https://www.youtube.com/watch?v=nx6M9w_TH7E
     
  11. KodiakBeer

    KodiakBeer Member

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    The M2 Is just a bad-assed piece of ordnance!
     
  12. phylo_roadking

    phylo_roadking Member

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    A trained no.2 in a Bren Gun team could change a barrel in 3-4 seconds...it was just flip up a clip and twist/lift away by the foregrip - then do it in reverse with the new barrel. I've also seen anecdotal accounts that bring it down to 2-3 seconds...!

    If it was done while the gunner swapped mags - then effectively it was no time taken.
     
  13. darkh

    darkh New Member

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    So would I. My instructors told me about diminished accuracy and even exploded barrels, but nothing about barrel stoppages. As a barrel gets hot it expands, offering LESS not more resistance to projectile passage. Eventually it gets to the point where the rifling is ineffective. However, weakened metal can cause the barrel to disintegrate right about this point. "Cook-offs" become a problem also. In Vietnam, for field troops, only the extended engagements when we were trying to break contact with a superior force cause the M60 to overheat sufficiently to require barrel replacement. In base defense, the clerk serving mandatory bunker duty frequently treated an M60 like a garden hose and destroyed the weapon after about the fifth "mad minute." For a couple of months of convalescence duty I was an army intel analyst; got bunker duty three nights a week and prayed we'd be assigned next to a bunker with 3MarDiv personnel. Even their cooks could at least shoot. And don't get me started on typewriter jockeys and hand grenades.
    The horror....
     
  14. USMCPrice

    USMCPrice Idiot at Large

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    I salute you for being a Vietnam Vet, thank you for your service! I was an M-60 gunner, MG squad and section leader and MG range instructor for a long time and have never seen a barrel stoppage. Never saw an exploded barrel, I have seen barrels surveyed because they became too hot and warped. I've seen many, many, cookoffs, the scariest is where the round cooks off while being extracted and bounces around inside the receiver. I agree an untrained, even marginally trained, gunner can wreck any gun rather quickly.

    Almost as dangerous are those that are around them so much they grow bored with them, or forget how dangerous they can be.
     
  15. lwd

    lwd Ace

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    I'm far from an expert but it would seem to me that for a stoppage to occur a series of extreme events would have to occur. For instance the barrel would have to have gotten hot enough to warp such that a bullet or bullets started impacting or wearing a point preferentiallyor expanded (or a combination of expansion and wear) to the point where the long axis of the bullet could turn so that it was out of alignment with the barrel. I have heard of some of the experimental sabot rounds for mg's actually exiting through the side of the barrel. Possibly some other sort of barrel failure could produce such a situation, like foregin material in the barrel damaging the barrel and going unnoticed.
     

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