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Subject: Instead of questioning the size of the bullets, why not debate the weight of the propellent ?
Rasputin    2/10/2007 12:48:21 AM
It seems that in morden fire arms development espeacially in the area of assault rifles, the focus has mainly been on the rifle itself, lighter weight, greater accuracy, mechanical reliability, red dot + laser optics, new lighter magazines, even highly effective muzzle breaks and compensators that allow u to chop the barrel length of the M16 to ridiculous propotions, yet be able to shoot normally. But apart from the bullet head and core (And for the 5.56, the verdict is still out on the best bullet type), the closest that anyone has come to really improving on the metal cartride had been the caseless ammunition by Heckler and Koch. Now the question here is how does the weight of American smokeless gun powder compare to that of the weight used by the Russians since 1947 for their ruskie rounds???? Can the United States develop a 7.62 X 57mm cartridge that is the same weight or lighter than the 5.56 round???? Using polymer plastic casings, kevlar or some new materials that need not be reloadable???? The rifles have improved, why not the bullets??? Does everyone believe that just because a round is standard and used universally it is good?
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Phaid       2/10/2007 11:29:19 AM
Nobody debates those things because they are not an immutable characteristic of the ammunition.  In terms of bullet head, cartridge, primer, and powder, anything you can do to a 7.62x39 round you can do to a 5.56x45. 

For example, look at the wildly varying quality between different AK round manufacturers -- US-made Winchester 7.62x39 rounds use a brass cartridge and unsealed Boxer primer, while Silver Bear rounds from Russia have a zinc-plated steel cartridge and water-sealed Berdan primer.  Both can be had in full metal jacket or hollowpoint.  Winchester rounds are reloadable and much more consistent in terms of powder and bullet weight than Russian ones are.  And Silver Bear is just one of many Russian manufacturers, and then you have the innumerable manufacturers from the rest of the world.

The point being, all rounds of the same type are not created equal, and the quality and characteristics of typical rounds of a given caliber don't really form a basis for comparing different calibers.
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tenX       2/10/2007 10:22:07 PM
Good thought, but material strength, propellant chemistry and interior ballistics conspire against improving propellants much beyond current state of the art.

Materials:  Ammo is loaded to keep chamber pressure within a safe limit.  It's bad form to overload - splitting barrels etc.  Until barrels and breech mechanisms can be made from higher strength materials, 60,000 PSI is about the top pressure that can be safely handled.

Propellant Chemistry:  There's not much more that can be done here, although the artillery people keep trying.  Liquid propellants have some promise, but current thechnology in this area has not proved to be successful yet.

Interior Ballistics:  The problem here is is just adding more propellant will not fix the problem..  If you plot pressure vs. time or distance the projectile travels in te barrel, there's a pressure spike at the beginning and one quickly loses pressure and acceleration.  The size and shape of the powder grains can be fiddled with to try to make the pressure curve more flat but most everything has been tried.

The "super guns" developed the Germans, and later by Gerald Bull used multiple chambers spaced at intervals along very long barrels to continue to accelerate the projectiles, but that would make for a very odd looking rifle indeed!

TenX out

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Rasputin       2/11/2007 12:50:08 PM
But is it possible with new R & D and the use of newer materials for cartridge casings and propellant which weighs less or requires less but provides the same kinetic energy to the 7.62 bullet head, ultimately providing ammo weight savings for the 7.62 to be comparable to the 5.56???
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Horsesoldier       2/11/2007 8:32:36 PM
>>>Can the United States develop a 7.62 X 57mm cartridge that is the same weight or lighter than the 5.56 round???? <<<
The bullet portion of the 7.62x51mm M80 ball round weighs 146 grains (total weight of the loaded cartridge is 392 grains).
The total weight (bullet, case, powder) of M855 5.56mm is 190 grains. 
In other words, just the bullet for the 7.62mm round weighs almost as much as the entire cartridge for the 5.56mm round.  Even with a polymer case or caseless round or whatever, you'd be lucky to get weight down to the mass of the conventional, brass cased 5.56mm round . . . unless you start eating into 7.62mm bullet mass, which rapidly starts costing you trajectory, energy retention, ballistic coefficient, etc. (though you can probably still get a round that is good for CQB and standard infantry work, even if it is not real great at 600 meters or whatever with a lighter bullet).
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Zerbrechen       2/11/2007 11:26:40 PM
   "But apart from the bullet head and core (And for the 5.56, the verdict is still out on the best bullet type), the closest that anyone has come to really improving on the metal cartride had been the caseless ammunition by Heckler and Koch."
   Not entirely accurate.  In the late 1980's and early 1990's, several manufacturers were all looking for the next big leap forward in assault rifle deelopment.  HK was working on the G11 which used a bolt that rotated 90 degrees to pick up ammo).  Steyr was developing the ACR which fired flechettes.  The flechettes were saboted and housed in a plastic case.  It was also diferent in that the primer on the cartridge was around the base of the cartridge.  The bolt moved vertically, basically crushing the primer on a pin at the top of the chamber.  Steyr learned what the US military learned 20 tears prior with the SPIW rifle... Flechettes aren't accurate and lack "stopping power."  Colt looked into using two bullets per cartridge, but again dropped the idea when it failed to produce real results.  Plastic cases are talked about every now and then, but I haven't seen any serious attempts at them, other than some training rounds.  They aren't as durable, and watch out for melting.
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Rasputin       2/11/2007 11:58:25 PM
If the lighter 7.62 is really is going to be impossible, then the next most interesting thing is to go for is the double tap.

And the so called impulse of the Abakan russian rifle that aids in spitting out double rounds at 2000 rds per minute, might give the 5.56 the edge in take downs.

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Jeff_F_F       2/12/2007 3:13:24 PM
As far as the pressure curve, the performance of modern tank rounds suggests that the propellant technology used in these weapons has largely solved this problem. Modern tank guns fire rounds at nearly the velocity of the expanding gas, which would only be possible if the pressure curve were nearly flat.
It should be noted that the 5.56 mm rounds we use are not being fired at the maximum velocity the type is capable of. Many 5.56 cartidges are capable of MVs in excess of 1000 m/s and the original 5.56mm ammunition fired at almost exactly 1000m/s.
However, I'm not at all convinced that more power is necessarily the answer. I've been doing a bit of research since the Big Bullet Blues discussion came up and what I'm seeing suggests that the basic problem is that what incapacitates a target is either destroying or somehow "turning off" the target's central nervous system. Destroying the CNS is a simple matter of head or spin shots, but those are hard to get in combat with any kind of consistency, and not all head shots actually penetrate the brain or spine. Turning the CNS off is much more complex. It seems to depend on a combination of neural "wiring" and psychology as much if not more than the amount/kind/location of the trauma inflicted by a bullet. I suspect that the reason that the medic cited in this discussion suggested that double taps that were inflicted against different parts of the body were more effective was that it was more likely to trigger the target's CNS to shut down than closely spaced impacts.
In my mind the main advantage of the G11 was that by firing accurate bursts it was more likely to inflict enough trauma to shut the target down.
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Jeff_F_F    Recent Composite Cartridge Work   2/14/2007 12:58:22 PM
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