New 6.8mm Offers More Stopping Power?

Discussion in 'Infantry' started by Yorkie, Mar 2, 2005.

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  1. This has been rumoured to be in service with US SF (but isn't everything?). However, the comments on 5.56mm vs 6.8mm are interesting. In outline (but please read the full article) :

    "Generally speaking, armor penetration is measured in inches (or fractions thereof) of steel plate. Both the 5.56mm and 6.8mm cartridges mentioned in this article won't penetrate a steel plate a quarter of an inch thick -- think Clint Eastwood's improvised chest plate in "A Fistful of Dollars" -- - but they can both shoot through all non-insert body armor types (though the 5.56 loses more energy on impact, and is significantly less lethal). So what's the other differences between them?

    What it all boils down to is that when the 5.56mm cartridge was first introduced to U.S. combat rifles, it was adopted because of its size and its fit with the U.S. "shoot-to-wound" philosophy of the time. While the 7.62mm NATO round used in the M-14 is much more powerful than the 5.56mm bullet, it is also much larger; a soldier can carry twice as many 5.56mm bullets as he can 7.62mm. In extended combat operations (wars lasting years), it was also estimated that wounded combatants would require more logistical support than dead ones -- with this in mind, the U.S. adopted the 5.56 round, since if the bullet did not kill outright, it would certainly cause a serious enough injury that the casualty would be hospitalized for a significant amount of time.

    Unfortunately, as demonstrated by recent conflicts such as Somalia in 1991, the 5.56 simply lacks the "shoot-to-kill" lethality (numerous accounts exist of Somalian insurgents being shot repeatedly before they finally either died or lost the will to fight) needed to stop an attacker. This shift in philosophy (from shoot-to-wound to shoot-to-kill) is what the 6.8mm SPC represents. Though not much larger than the 5.56 round, it is undeniably more lethal. The real world effect of adopting this round can be seen how CQB (Close Quarter Battle) is conducted. In a room-by-room fight, the more rapidly an enemy combatant can be taken out, the safer the operation is for friendly forces. Since there's no time to evaluate a target's condition in a firefight, soldiers engaged in room-by-room combat will shoot each individual 3-5 times to ensure that they are dead. With a heavier, more lethal round, they need only shoot 2-3 times. While this may not seem like a significant improvement, it can shave valuable seconds off of engagement times (as the shooter shifts between targets) and mean the difference between having bullets left over at the end of the fight -- or having to swap magazines while surrounded by live bad guys. "
  2. Does 6.8mm offer more stoping power [than the 5.56 fodder we feed our SA80s]?

    Depends on the bullets construction, the velocity and the weight of the bullet.

    Assuming similar construction and broadly similar velocity and a sensible weight-for-calibre, say 130 grains, then the answer is likely to be yes, at a price of heavier ammo and heavier recoil, doubtless leading to less accurate fire from your average Tommy.
  3. thought the 5.56 was only designed to maim anyways taking more soldiers out of the field to look after the casualty?

    i.e one wounded scrote needs a medic plus 2 x stretcher bearers, therefore taking 4 people out of the field.

    whereas one corpse stays where it is... till its burried later.

    ahhh you covered that... oops... am a mong
  4. Dirt_Diver

    Dirt_Diver LE Moderator

  5. Wouldnt 6.8 mil be harder to get up the spout in a 5.56 rifle 8P
  6. Nah, after the first one, you don't worry about it too much. Seen the results of a 5.57 round in a Cadet GP rifle...
  7. When the US adopted the 5.56 cartridge, they beleived its higher velocity, low recoil and lighter weight would mean that there troops would be able to successfully engage an enemy accurately at longer range than his weapons, pin him down , and call for support, be it heli, gunship, mortars, arty, etc; This has been there battle doctrine since WWII. Ie; contact, pinpoint, withdraw, call down fire. That way, war costs much more, but they can afford it and less GI's go home in body bags.

    But at about the same time as adopting a .223 or 5.56 cartidge, the SS109, they got embroiled in a jungle war in Vietnam. Even when not in jungle, such as the central highlands, the enemy would pop up yards away from tunnels. Ranges were considerably shortened. They found that the new round lacked immediate stopping power, but in terms of lethality it was very nearly as effective as the 7.62x51. It just took longer for the enemy to lie down and die. cos shock, blood loss and trauma were not so immediate.

    Added to the fact that at the height of the 'asian vacation' years 65 to 68, they were up against the best fighting cadres the of the NVA and VC, some of them 20 year veterans with a tenacious spirit.

    Then, it gets political. In order to justify a rifle/cartridge combination that is rumoured to be ineffective, (and in some but not all respects, it was) the D of D says that the great thing about this round is it is strategic, not tactical. Ie: it creates a great quantity of wounded, and clogs up the enemy logistics in their rear areas, their 'combat veins'

    That is of course a lot of bovine scatology, from the viewpoint of the grunt in the grass, who is being overrun by by NVA main force and screaming 'broken arrow' into his radio!

    The 6.8mm is a stopgap option. Current M16A2 uppers can be rebored and rechambered to accept the new cartridge. (or an entirely new upper can be substituted) Apart from the neck, the cartridge dimensions are the same. The weight increase is negligible. They even fit in the current M16/Diemaco/Orlite mags, and will still hold 30 rounds without any modification. Recoil and handling and bullet drop is said not to be much different from the 5.56 round. 6.8mm uppers are already commercially available for private owners in the states.

    Its a good idea. Its cheap. It will require little or no retraining. It will do until Arnie gets his 'Pulse rifles in the fowetty-megawatt range'
  8. We had a NZer transfer to our Bn. He recounted an episode from Vietnam when the Kiwis had just arrived. It would appear that the locals had a nice trick with the US troops of firing and then hiding behind termite hills in the knowledge that the 5.56 would not get through. They were very surprised and dead when the nasty Kiwis fired 7.62 right through the termite hills.

    The yanks have been complaining about the m16a2 (take not all who think it is a wonder weapon) for a long time and questions have been asked in government. They are very happy with the m4 though. It would appear to be the weapon that is the problem as much as the ammo.

    We had an incident in the US in 88 when my Bn was there. We had a range day for the head shed, a you can lay with ours if we can play with yours as both the SA80 and M16A2 had both only been in service a short time. As we were hosting the day we provided Reggy Grunthorps ammo for both rifles and a good time was had by all. When the US armourers cleaned the M16s they found that our ammo had damaged the barrels. From that point on only Green spot (US ammo) was to be used by the Lt Div coy attached to our Bn. It would appear that our SS109 was not the same as the US SS109.

    I seem to remember seeing someplace that the 4.85 had better stopping power than the 5.56. As to why it did not win I have no idea.
  9. Faster round ie more kinetic energy (KE=0.5mv^2)? Don't know.

    The thought of having to lug around 7.62 rounds does not particularly appeal to me. If it boils down to having to having half as many rounds as you would carrying the smaller calibre I would think most would choose the 5.56. On the face of it the 6.8mm sounds ideal but I have yet to see what kind of a hole it makes.
  10. The original US Army .223" (5.56mm x 45mm) 55 grain (3.56g) M193 bullet was notorious for rapid tumbling, coursing more damage at intermediate ranges. but the current NATO 62 grain (4.02g) SS109/M855 bullet is fired from rifles with a much steeper rifling twist (1 turn in 7 inches - 18cm - instead of 1 in 12 - 30cm) is supposed to be interchangeable! But more than one report has proved it is not 100% inter-changeable.

    Green Spot is just a tighter controled batch, and normally are the first rounds produced from a production die set.

    The Enfield 4.85mm x 49mm XL Series was only a necked down and stretched 5.56mm case and was the same from below the shoulder, and had a higher muzzle velocity.
  11. Tell me more about this 5.57 round Bob.

    Looking at my copy of Cartridges of the World I am struggling to see a listing...
  12. Reboring in a new diameter is an extremely expensive option. I looked at it once on one of my hunting rifles. Boring out a 6.8mm hole from a 5.56mm tube is going to result in very thin barrel walls for a start.

    Far cheaper is rebarreling. Unscrew old barrel, screw in new barrel. Job done. No need to cut a new chamber either as the new barrel will have one factory cut.

    If bullet drop (trajectory) is to be unchanged then to fire a (130 grain 6.8) bullet aproximetly twice the weight of the (62? grain 5.56) in the same weight rifle then recoil is likely to be doubled. Laws of physics.

    That said, I do not understand how, if case dimesions are unchanged, a bullet double the weight of the old can be launched along the same trajectory. The pressure increase must be massive.
  13. Another Failed Calibre - Enfield played with 6.25mm in re-bored EM2 280/30" rifles before trying 4.85mm
  14. It's been my experience that it's not WHAT you hit them with, it's WHERE your hit them.

    The rule of thumb I gave my Soldiers was "Center of Available Mass"; meaning whatever portion of the target is seen, aim for the middle of it. Make a follow-up shot if necessary.

    I've dropped people with a single 9mm in CQB situations. I've shot people with a .50 cal round and they got up and continued to engage me. Several more .50 cal rounds rectified the problem...

    I think that "Stopping Power" is a holy grail for some; whereas reality dictates that marksmanship and tactics carries the day. I've yet to see a reliable one-shot stop for light weapons; nor have I seen any light weapon round perform significantly better than another.