Thread Follow-Up: The Ultimate Combat Rifle

[Nolo]

If you haven't looked at it, is the parent article:<a href="http://www.thehighroad.org/showthread.php?t=292713">Ultimate Combat Round</a>, it's pretty necessary to understanding what's going on here.
So, I've basically figured out the "ultimate combat round", even though all of us understand there's really no such thing. Anyway, I've come to basically two choices:
A 5.56mm telescoped cartridge that's 35mm long, the same length as a 7.62x25 Tokarev round:

Caliber: 5.56mm
Weight (Projectile): 90 grains
Length: 35mm
Width: 9.6mm
Weight: .016 pounds
Velocity: 3,000 f/s
Energy: 1800 ft-lbs
TME (40-round magazine): 72,000 ft-lbs
EPP: 112,500 ft-lbs
Main advantage: Short OAL allows the magazine to be inserted into the grip, which is the most ergonomic place to have a magazine, not to mention it makes the rifle shorter (though not as short as a bullpup).
Main disadvantage: No taper or neck on the case could cause feeding problems.

A 6mm telescoped round with a more conventional layout, approximately the same length as the 7.62x39 M43 round. Has a very deep-seated bullet to keep OAL down:

Caliber: 6mm
Weight (Projectile): 100 grains
Length: 55mm
Width: 9.6mm
Weight: .020 pounds
Velocity: 3,100 f/s
Energy: 2100 ft-lbs
TME (35-round magazine): 73,500 ft-lbs
EPP: 105,000 ft-lbs
Main advantage: Round is extremely powerful, more powerful than 6.5 Grendel, as well as possessing good long range performance due to high BC.
Main disadvantage: Relatively large cartridge (compared to 5.56 FA) means that magazine must be either behind or in front of the grip.

Either round would work, depending on the rifle chosen. That's the point of this thread: to choose and/or design a rifle that would facilitate one of these cartridges.
Since each round has specific and different nuances, a distinctly different weapon would be needed to use them. For the 5.56, a weapon similar to a submachinegun would be desirable, as it conserves length and cartridge sizes are similar. For the 6mm, a weapon similar to an AK, Galil or AR-15 would be fitting, as they would be able to take advantage of the round's long-range performance and their size would dampen recoil.

Potential models for the 5.56mm rifle:
FN P90
HK MP5
IMI UZI
Calico SMG
Kriss Super V
Steyr ACR
IMI Tavor-21
AKS-74U (Krinkov)
XM8 PDW
AEK-971 and AK-108
All of these weapons are small, capable of taking advantage of a small cartridge, but, if chambered for the 5.56, would pack far greater firepower than the parent weapon. Of note, nearly all of these weapons have barrels that are shorter than the desired length for the 5.56mm weapon. That's easily fixed, however.

Potential models for the 6mm rifle:
Steyr AUG
FN SCAR
HK G36
HK 416
IMI Galil
IMI Tavor-21
AK-47 line
AEK-971 and AK-108
ArmaLite AR-15
XM-8
These rifles all have certain feature that could be desirable on a classic assault rifle. The AUG, SCAR and XM-8 have versatility. The Tavor is compact. The AK is hugely reliable. The AEK and AK-108 have balanced gas systems. The AR-15 is light.

So, first off, which of these cartridges do you think is the better one? Which caliber line of weapon should I go with?

 

[Nolo]

Crapola. How do you get those darned links to work?

 

[Rifleman 173]

The .223/5.56 has been a weak bullet for over 40 years now. I remember when they first gave us the M-16 rifles in Viet Nam and we were required to use them. We all hated them! Since then the ammo has remained lousy and ineffective which is why our troops in Iraq and Afghanistan switch, when they can to the 7.62 X 39 AK type rifles.

Your minimum bullet weight should be no less than 120 grains. One thing that present day gun designers fail to take in consideration is that around the world most nations allow the VERY liberal use of narcotics. In Nam some of the combat we had involved the Americans facing doped-up Communist troops. When you have an enemy soldier who is stoned to the gills with opium or morphine or whatever, shooting him with a wimpy bullet that has no weight does NOT produce an immediate terminal effect. It should have good velocity like the present .223/5.56 bullet. The bullet should be more like a spear (long and thin) than like a dart (the 55 grain .223). The long and thin design of the bullet "should" give it good aerodynamics and make it pretty darn accurate to shoot. Keep in mind that I am NOT urging a re-invention of the AK-47 (7.62 X 39) cartridge. What I am suggesting is a new round based upon new materials and technology. One other thing... I would make the minimum caliber size to be a .30 caliber or 7.62 size bullet. Anything smaller will just create another useless bullet that our military personnel will hate for 40 years.

 

[Nolo]

Your minimum bullet weight should be no less than 120 grains. One thing that present day gun designers fail to take in consideration is that around the world most nations allow the VERY liberal use of narcotics. In Nam some of the combat we had involved the Americans facing doped-up Communist troops. When you have an enemy soldier who is stoned to the gills with opium or morphine or whatever, shooting him with a wimpy bullet that has no weight does NOT produce an immediate terminal effect. It should have good velocity like the present .223/5.56 bullet. The bullet should be more like a spear (long and thin) than like a dart (the 55 grain .223). The long and thin design of the bullet "should" give it good aerodynamics and make it pretty darn accurate to shoot. Keep in mind that I am NOT urging a re-invention of the AK-47 (7.62 X 39) cartridge. What I am suggesting is a new round based upon new materials and technology. One other thing... I would make the minimum caliber size to be a .30 caliber or 7.62 size bullet. Anything smaller will just create another useless bullet that our military personnel will hate for 40 years.

I disagree with this statement. I think that .30 caliber minimum for a round is unreasonable. In order to send a .30 caliber bullet fast enough to have flat-enough-shooting performance, you are basically redesigning the .308 Winchester. Which is fine, if you do it right. I already did that, though. It came out as an M43-sized .308 Winchester. If you have a high-velocity, light weight bullet, then you get significant performance provided you have adequate fragmentation. .223 is admirable in this respect. Its long-range use and weight are what concern me the most.

 

[Rifleman 173]

I've shot people with both the 5.56 NATO and the 7.62 NATO bullets. The 7.62 NATO works while the 5.56 lacks a lot effectiveness. Where it takes one round for the 7.62, it often (overseas) takes 3 to 8 rounds of 5.56 ammo to work. The effectiveness of the 7.62 rounds is more immediate than that of the 5.56 ammo. You hit a guy in the chest with a 7.62 ammo, most often he'll spin around, fall face down to the ground and not move any more. Do the same hit to the chest with the 5.56 and the guy will fall backwards, look down at his wound, get up and try to move away. This is what our troops are dealing with, again, in Iraq and Afghanistan which is exactly why they're using captured AK-47 type rifles AGAIN!! Weight of the bullet, speed of the bullet and diameter of the bullet are what makes the .30 caliber/7.62 ammo more EFFECTIVE than the .223/5.56 ammo. If your theory were right about fragmentation of small caliber bullets, our military should then be carrying .22 Long Rifle firing guns because those rounds also are small bore ammo travelling at high speed. Heck, that would even be more cost effective (cheaper) than using the more expensive center-fire ammo. Go with some new technology, new materials and design a really good 7.62 bullet of some sort. Why do you think that our military is trying to bring the 6.8 SPC into play? It's because, again, the small, fast ammo is NOT WORKING effectively and hasn't proven effective or popular with our troops since the 1960s. I could see somebody taking a good 6.5 millimeter or .270 Winchester type bullet or something close to that and maybe making it work BUT, just to be safe, the minimum caliber I would feel safe with would be the 7.62/.30 caliber ammo based upon MY experiences. I'm just making suggestions based off of what I've seen, done and know. Your experiences may be different and are just as valid as mine BUT I tend to think that by sheer logic the .30 ammo will prove itself, again, over the light, fast bullets.

 

[Nolo]

You hit a guy in the chest with a 7.62 ammo, most often he'll spin around, fall face down to the ground and not move any more. Do the same hit to the chest with the 5.56 and the guy will fall backwards, look down at his wound, get up and try to move away.

You are correct, but that has little to do with bullet diameter and more to do with bullet energy (a bullet from a 7.62N has a little less than twice the energy of a 5.56). If you made a cartridge that had the same energy as a 7.62N but was of 5.56mm diameter, my educated guess is that you would find similar performance from it.

Weight of the bullet, speed of the bullet and diameter of the bullet are what makes the .30 caliber/7.62 ammo more EFFECTIVE than the .223/5.56 ammo.

Weight, yes.
Speed, yes.
Diameter, no; at least not as much.

If your theory were right about fragmentation of small caliber bullets, our military should then be carrying .22 Long Rifle

small bore ammo travelling at high speed

.22LR is not high speed.
.22LR doesn't fragment well; it only goes at 1200 f/s tops.

Why do you think that our military is trying to bring the 6.8 SPC into play? It's because, again, the small, fast ammo is NOT WORKING effectively and hasn't proven effective or popular with our troops since the 1960s.

The military isn't trying to bring 6.8mm SPC into play, they're resisting a change. 6.8mm SPC has an advantage in first-hit kills. I suggest a 40-round coffin-style magazine in a high-velocity, lightweight caliber (i.e. .223 or one of the 5.56 Firebrands), that way you can effectively utilize a two-shot burst setting and I think you will find the effectiveness increase dramatically. As for not being popular with the troops, I haven't heard anything to really back that up. Over 83% of troops nowadays approve of the M16/M4 system, and that includes the 5.56mm round.
Bullet weight is important. I would note that I am NOT working with 55-grainer 5.56s, I'm working with 90-grain 5.56s, a significant increase. The total energy of a 5.56 is roughly 1300 ft-lbs of energy, whereas my 5.56 rounds produce upwards of about 1800 ft-lbs of energy (more than a 6.8 SPC), some producing up to 2500 ft-lbs energy (as much as a 7.62 NATO). Light and fast fragments well, has a laserlike trajectory and is lighter than heavier setups, making it overall more desirable. Causing death in a victim with a firearm is not about hitting them with enough force to knock them over, it's about opening up enough arteries and veins to (through rapid blood loss) cause shock and death. The best way to do that is with a fragmenting bullet that rips into pieces that tear their way through the body. You do that with higher velocities. And, unless you want the main service cartridge to be .338 Lapua, then you do that with a smaller bullet.

 

[HorseSoldier]

I'm not entirely certain what the point of some of these discussions is, when you have such patently untrue statements as:

Since then the ammo has remained lousy and ineffective which is why our troops in Iraq and Afghanistan switch, when they can to the 7.62 X 39 AK type rifles.

Passed off as some sort of fact.

Some guys picked up AKs in Iraq during the invasion because their issue personal weapons were M9 pistols and they were suddenly doing foot patrols or humvee patrols rather than crewing tanks and such. Any long gun is better than no long gun at all.

Unlike the AK, our issue weapon is actually designed for trained gun fighters, and it works. The bullet has been killing people for decades and is pretty close to the world standard for service rifles (count it's Russian and Chinese imitators and it simply is the world standard). Being in a portion of the army where people have extremely high levels of training with weapons and could use the AK in theater if they wanted (at least team guys), I think the fact that no one uses them pretty solidly clears up any issue of admiration for the AK by the majority of US troops.

 

[Nolo]

*high fives HorseSoldier*
Said it like it is.