The Ultimate Combat Round

[Nolo]

I have to hand it to you, GunTech, considering only normal propellants and technologies and with the current combat situation, your 6.5x45mm round really is the best. It's a compromise, but it's a compromise that gets you the second-best in all worlds, which is how compromises should be. I really think you've cracked it. I realized that my 5.56 Zephyr (subconsciously) was really designed for a sniper machine gun. That is, it was designed to lay down full-auto fire really accurately at really long ranges. This was largely influenced by what I was designing at the time, a big, scoped, long-barreled battle rifle:

I did not design the Zephyr and the battle rifle in concert, the battle rifle was originally designed for a 6.7x45mm cartridge (a lot like your 6.5 GT now that I think about it, 117-grain at 2800 f/s out of an 18-inch barrel...). It was basically designed to lay down bursts of full-auto fire at really long ranges.
I don't think that's what we need nowadays. We don't need that range, but I was focused on speed. Speed that I'm not sure we need either.
Oh well.

 

[HorseSoldier]

Based on what I've learned so far, I believe organic weapons are the weapons used in the immediate squads in the platoon. These are the individual weapons like the assault rifle, marksman rifle, SAW, grenade launcher, disposable or reusable rocket launcher.

The term "organic weapons" simply means any given unit's assigned weapons. It is not limited to any particular unit size, so you can talk about weapons organic to the infantry squad, a tank platoon, a rifle company, etc.

Whether or not a squad has an organic medium machinegun depends on MTOE. It's not an organic squad weapon in a classic light infantry/infantry kind of unit where MGs are a platoon asset, but in a mechanized unit there you have the "mobile arms room" concept to an extent with each squad having an M240 (which may or may not be carried by dismounted troops, depending on mission). It is not an assigned personal weapon, but is organic to the squad.

 

[HorseSoldier]

The .276 Pederson round that was originally slated for the Garand has excellent potential. Only its overall length seems to count against it for modern assault rifle use.

You could get the numbers 276 Pederson was clocking back then with a shorter case these days. Both 6.8 Rem SPC and 6.5 Grendel actually come fairly close to the load in terms of muzzle energy, though both do it with lighter bullets at higher velocity if my memory serves me correctly.

 

[Nolo]

I'd do .276 Pedersen with a 6.5mm bullet and a 7.62x39mm case if I were gonna do it now. Oh, wait, I just made 6.5 Grendel!

 

[Roswell 1847]

the 9mm ball round drops muslims dead!

Reports from the field indicate otherwise.
Some of those rejects are hardcore and don't let a few holes even distract them from their mission, like the Japanese they are ready to die so they don't let eminent death bother them that much.
Plus Body armor has been showing up in jihadi hands for some time now. Not enough to equip many fighters but enough to make dealing with a suicide squad much more of an adventure.

The Infantry weapon of today should be able to penetrate thick doors and cinderblock walls at the very least. It should be able to chew a rathole in a thick adobe wall big enough for the thumper to do its work.
WW2 Street fighting and house to house tatics called for cutting holes in stone walls using a BAR to get from one building to another if neceassary. There were also instructions on how best to do this using a Thompson.

 

[pete f]

take a .40 S&W case head, stretch it out to 45 mm in length, load a 110 grain 6.5 mm bullet to about 2950 FPS. then change the basis hand gun to .40 S&W and offer a PDW in 10 MM, ALL have the same case head, bolts mean you can offer differening uppers for variety, and you get a small enough case to get decent capacity out of standard 30 rounds mags, and yet get enough punch for the next war which might be in China, or northern India or where ever, where foilage and range might be an issue again.



Idealy, I want a 50 BMG punch, in a .223 package, that recoils like a .22 lr in a 5 pound rifle thats accurate to 700 yards. When you revive Einstein and get him working the physics of that one out, let me know. or until someone brings back a "40 watt phased plasma rifle"

 

[Evil Monkey]

The Infantry weapon of today should be able to penetrate thick doors and cinderblock walls at the very least.

I do not agree with that. That's a waste of ammo.

You got a barricade to get through? Use explosives, that's what they're there for. You have 40mm, AT4, vehicle mounted heavy weapons. That's what takes care of hard barricades, not hand held small arms.

 

[Ignition Override]

Don't Tread On Me, NOLO etc:

Very interesting. PBS' Frontline did an interesting expose recently on the Iranian Quds special forces, and the weapons smuggled into Iraq to use on our troops.

The axis of China, Iran, Syria, Hezbollah in Lebanon/Israel/Egypt is a very major, nasty threat, even without lots of help from the Russians, who appear to sell anything they can to anybody, being partly bankrupt (despite lots of undrilled oil under Siberia, far from ports).
Wasn't it nice of Nancy Pellosi to visit Syria recently-ironic with Syrian support of terrorists for decades (when we attacked Libya in '86 with F-111s from RAF Lakenheath and some carriers in the Med, intell. later revealed that Syria was probably the main culprit)?

Among these different nations, what effective combat rifle is produced and exported/smuggled in large numbers which are NOT similar to the AK-47 types?

Looking forward to taking a friend today to shoot some pumpkins and large white tropicana juice jugs.
Will pretend that they are Taliban/Al Qaeda. My first time with a real AR-15!
Will compare pumpkin 'wounds' between his .223 and my .30 Carbine. :

Which leave a larger hole in back of empty pumpkins, if his are solid .223 copper jacket rounds?

 

[Tony Williams]

I may not be da bestest at fizziks, but this cannot be true. You cannot launch a 123gr projectile with approximately seventy percent of the mass of your control round (7.62x51 175gr) at a similar velocity and achieve a 50% reduction in free recoil. Moreover, you cannot chamber that round in a lighter weapon and achieve a 50% reduction in felt recoil.

There are two reasons why this could be true.

First, bullet momentum is the largest contributor to a cartridge's recoil impulse but not the only one: the gas escaping from the muzzle makes a major contribution too. The rough formula for calculating the recoil impulse is:
(bullet weight x muzzle velocity) + (propellant weight x 4,000 fps)
since 4,000 fps is about the average velocity of gun gas as it leaves the muzzle. As you will see, a very compact and efficient cartridge like the 6.5mm Grendel is going to use less much propellant than the 7.62mm NATO.

The second reason is that if you have two cartridges, one with twice the recoil impulse of the other, and you fire both in otherwise identical weapons, the gun firing the more powerful cartridge will travel backwards in recoil twice as fast. But if you look at the energy involved, rather than the momentum, then a similar gun travelling twice as fast actually generates four times as much recoil energy (energy being calculated using the square of the velocity) - and that's what the shooter feels on his shoulder.

 

[Tony Williams]

I would not argue for one all-purpose military round just for the sake of it: as already observed, logistics can handle several cartridges if need be.

However, there seems to be a lot of agreement that, if all existing weapons and manufacturing facilities vanished so we had to start with a genuine clean sheet, something more powerful than the 5.56x45 would be desirable as a standard military rifle calibre, but with less size, weight and recoil than the 7.62x51. Something, in fact, rather like the 6.8mm Rem or 6.5mm Grendel.

There isn't much to choose between the 6.8mm and 6.5mm, when loaded with bullets of similar construction, as rifle ammo. However, the 6.5mm has the advantage of a much better long-range performance: close enough to the 7.62x51 for the latter to be unnecessary. So it could fulfil the role of a genuine dual-purpose rifle/MG round without any significant compromise to its effectiveness in either role.

As I've observed before, this isn't going to happen: for financial reasons, we are stuck with the 5.56x45 + 7.62x51 combo until someone comes along with something radically different. But I can see that in a couple of decades, a new plastic-cased or caseless telescoped round with ballistics similar to the 6.5mm Grendel could well be the standard rifle/MG round, with ammo weight similar to the current 5.56mm.

 

[lencac]

Assuming we are talking about the rifle type being auto-loaders the round would need exterior characteristics that allow the firearm to cycle ammo correctly and reliably.
USMC fighting rule #10. Use! a gun that works EVERY TIME. "All skill is in vain when someone
pisses in the flintlock of
your musket."
Having said that it seems to me that some type of 7.62x51 NATO cartridge necked down to 6.5 mm would be a very versitile round. We all know the wonderful versitility of the 6.5 round. Many different weights available from say 100 gr. to 160 gr. Great sectional density. Tremendous long range ability. Excellent BC. And depending on the intended usage they could be combo of different charges and bullets to accomplish the different tasks needed.

 

[Tony Williams]

Having said that it seems to me that some type of 7.62x51 NATO cartridge necked down to 6.5 mm would be a very versitile round.

It would be fine for semi-auto and MG use, but IMO the size, weight and recoil would be too much for an automatic assault rifle.

 

[lencac]

Tony ..... maybe light bullet and bit lighter charge?

 

[PercyShelley]

PercyShelly,

I'm now wondering of you've read liquid propellant gun technology by Klimgenberg et al

Alas, I have not Guntech, and the copies listed on Amazon are priced rather unreasonably.

Summary?

 

[GunTech]

PercyShelly,

I'd be happy to loan you my copy. It's a dense and technical read, but interesting. PM me your address and I'll send it to you.

My primary interest is actually ET and ETC guns, and the book has I think a single chapter on that, but there is even less published technical info on ETC than there is on LP guns.

 

[GunTech]

Evil Monkey

RE: the M249.

I've had several friends who were deployed in the sandbox tell me that the M249 has proved to be a less than stellar weapon that need some work. This is backed up by official reports from the field.

for example:

Though were minimal maintainability and reliability issues raised, a number of universal issues were voiced related to the M249 SAW maintainability, the M203 durability, lubrication types, and magazines. SAW gunners were unanimously dissatisfied with the complexity of the M249 SAW. Its numerous small parts encumbered field stripping and were easily lost. Some SAW gunners resorted to extremely unorthodox methods to retain weapon availability. The M249 SAW was the most problematic weapon in the theater.

from a report entitled "PROJECT MANAGER SOLDIER WEAPONS

SOLDIER WEAPONS ASSESSMENT TEAM REPORT 6-03

OPERATION IRAQI FREEDOM"

Which can be viewed here:

http://www.bob-oracle.com/SWATreport.htm

 

[GunTech]

Nolo,

I don;t think 6.5x45 is the best packaging, but the round was designed to use existing cases so that any wildcatter could produce the round. Ideally, you'd design everything off-the-shelf to get what you really want.

It should be noted that the parent 7.62x45 case had a PMax of 4300 bar, compared with the 4050 bar used in the 6.5x45 and 6.5 Grendel. If your platform could handle the higher pressure of the parent round, you can gain some velocity, but at the cost of muzzle blast.

If you are really creating an round that falls between 7.62 NATO and 5.56, your bullet is 6.5mm, weighs 106 grain and has a case head size of 0.428. This is pretty close to the 6.8 SPC case. Apparently, the testers tried the 6.5 bullet in the 6.8 case and found it wanting.

 

[Tony Williams]

maybe light bullet and bit lighter charge?

Then you could use a smaller cartridge case - like the 6.5mm Grendel's

I think that the Grendel and the 6.8mm Rem are probably around the maximum power for reasonable controllability in auto fire in a rifle (yes, I know that's an individual thing, but if you're equipping an army you have to think of the average guy).

 

[GunTech]

Having said that it seems to me that some type of 7.62x51 NATO cartridge necked down to 6.5 mm would be a very versitile round. We all know the wonderful versitility of the 6.5 round. Many different weights available from say 100 gr. to 160 gr. Great sectional density. Tremendous long range ability. Excellent BC. And depending on the intended usage they could be combo of different charges and bullets to accomplish the different tasks needed.

You've just describe the 260 Remington. A great cartridge, but unfortunately requiring a large rifle and weighing about the same as the 7.62 NATO.

The 260 does have better ballistics than the 308, and less recoil, and I'd be curious to see how it would handle under full auto.

But it seems too heavy to be a good assault rifle cartridge.

 

[Tony Williams]

Apparently, the testers tried the 6.5 bullet in the 6.8 case and found it wanting.

That doesn't surprise me. If you want to use a c.120 grain bullet (which seems to be about the optimum fo the calibre) then it would have had to be seated deep in the case, and since the 6.8's case is narrower than the Grendel's, there would have been less room for propellant.

I think that the Grendel's case dimensions are probably the optimum for a 6.5mm cartridge which is short enough to be used in an AR-15 action.

 

[GunTech]

If we use the AK in 7.62x39 as a baseline for manageable recoil, we are looking at about 8 Joules if recoil energy. Assuming a 9 pound infantry rifle, the 6.5 Grendel with a 123gn bullet going 2475 has slightly more recoil, at around 9 Joules. The 6.8 SPC with 115gn bullet is identical to the AK at 8 Joules.

If we take out mythical 'in-between' 6.5 firing a 108gn bullet at a predicted 2640 fps from a 16 inch bbl, we get a recoil energy of about 8 Joules as well.

For comparison, 5.56x45 M855 has about 5 Joules of recoil energy in the same 9 pound rifle.

 

[GunTech]

Depending on bullet weight, you can tweak the 6.5 grendel case for slightly better performance, or adjust its contours for better feeding.

But it should be remembered that the 6.5 Grendel was limited by its parent case, and was designed initially as a target round. In that role, little body taper is not an issue, and a steep shoulder is actually desirable.

Since the 6.8 SPC was designed from the outset as a combat round, it has the body taper and shoulder angle typical of other military cartridges.

 

[HorseSoldier]

The Infantry weapon of today should be able to penetrate thick doors and cinderblock walls at the very least. It should be able to chew a rathole in a thick adobe wall big enough for the thumper to do its work.

There's not much right about this concept, in my opinion.

First, "chewing through walls" = "wasted ammo." If you're a belt fed MG with a few thousand rounds on hand, it may be a workable idea in some cases, but for the infantryman or other guy with a carbine and his 210 rounds basic load + whatever else he could squirrel away on his person (or less, if you're using bigger and heavier rounds) trying to blindly fire through walls is just poor fire discipline.

Second, "chewing through adobe walls" is just a silly premise, I'm sorry. The walls in question, at least in the Middle East, are standing up to repeated hits from .50 cals and 25mm cannon. Nothing Joe's going to be shooting from his shoulder besides an AT-4 or SMAW is going to get that job done, regardless of caliber.

Finally, if the goal is to let the 40mm grenade launcher get through a wall, why not just let the 40mm grenade launcher make the hole too? HEDP will penetrate a couple inches of steel armor plate, and is going to do a better job on structural walls than an entire basic load of 5.56, 7.62x39. or 7.62x51 through a rifle. If that won't work, as Evil Monkey suggested, go bigger -- we don't issue AT-4s just to build character. If that won't do it, call in arty, CAS, a gunship, a tank, whatever . . . but don't compromise the fightability of the individual rifle or carbine by saddling it with irrelevant and unrealistic performance requirements.

 

[Evil Monkey]

for example:

Though were minimal maintainability and reliability issues raised, a number of universal issues were voiced related to the M249 SAW maintainability, the M203 durability, lubrication types, and magazines. SAW gunners were unanimously dissatisfied with the complexity of the M249 SAW. Its numerous small parts encumbered field stripping and were easily lost. Some SAW gunners resorted to extremely unorthodox methods to retain weapon availability. The M249 SAW was the most problematic weapon in the theater.

I see. I thought you were going to state there was a problem with the 5.56mm from the automatic rifle/light machine gun in the urban landscape of Iraq.

 

[Nolo]

Hmmm... I've looked a lot at 10.5mm case heads and I like them. They're bigger than a 5.56's, but they're smaller than a 7.62's. I think that around 6.5mm is the ideal cartridge caliber. 6.3, 6.5, 6.7, 6.8, I think they all would do fine.
However, I can't help but think of the advantages of a super-flat-shooting 5.56mm caliber. You don't have to adjust your sights as much, you can still get some beastly terminal effects and you can do DMR work if you're not afraid to pop off a few shots.
Just look at how the Mk. 262 has performed. I think that you can significantly improve on that caliber's performance if you are willing to go to a new caliber.
What about 5.45 necked up to 5.56mm? Use an 82-grain streamlined Scenar-type bullet and shove that puppy at about 3000 f/s.