New Army "Caliber Configuration Study"

[stanc]

On the contrary, I have no doubt a 6.5mm ball round can match the BC of a SMK. Why? Look at the 7.62N 147gr FMJ. Meplat is already very small, no bigger than an HPBT. Ogive is already very sleek, damn near secant.

That's because it is a secant ogive.

Okay, let's assume that you're right. The 6.5mm 107gr MatchKing has only a 0.406 BC. Combine that with the probable muzzle velocities from 14.5" (carbine), 16" (DMR/IAR), and 18" (LMG) barrels. What ballistics do we get? Good enough to make 6.5G viable against the PKM?

I guess I'm assuming that in a real shooting war with China that, somehow, the grown-ups will be back in charge and green bullets will take a backseat to the steely-eyed dealing of death.

Would it be rude to point out that China, Russia, and other potential enemies have been using "nearly-green" (steel-core) bullets for decades?

"Eco-friendly" doesn't necessarily equate to ineffective.

[nincomp]

As the US seems to be set on lead-free bullets, before long, the reference 7.62x51 round will be something like the the M80A1. I have no idea what this will end up being, though.

[JASmith]

Going with an Iron or other eco-friendly bullet will cramp one's style a bit. If we do see an intermediate caliber designed to accommodate that handicap, just think what will happen when we do free-up the constraint?

Won't necessarily happen, but it is nice to have margins.

[nincomp]

Backing up a bit to the discussion about MMGs vs ABGLs, 84mm CGs, etc.

I may be missing something, but when the ABGLs, CGs, Laser-ranged rockets/grenades and Hanka's HVRSFLRABGL (see post 280) are discussed, are these still of the of the shoulder fired, non-guided variety? If so, it would take a hell of a marksman to consistently get within a few of meters of an enemy taking cover behind a boulder at 1000 yards.

If these weapons are unguided, a bunch of ammo would be needed, since multiple shots would likely be needed for each target at long distance. If the group were receiving fire from multiple directions, the ammo burden could be quite large.

If there is a desire for one-shot accuracy and if some form of guidance mechanism was not added to the above projectiles, we are left with some kind of TOW or javelins. The last I checked, javelins cost many shitloads of dollars each.

The high cost of weapons actually ties in to my thoughts on the Evolution of War thread. In short, Americans would find themselves hit in their most sensitive spot--- their wallets.

[stanc]

You can have cheap. You can have effective. Don't expect to have both.

I wouldn't worry much about the cost of infantry weapons. That's a relatively small share of the DoD budget.

[nincomp]

Stan, you are right, but the cost of infantry weapons seems to be something that the public and Congress can relate to. After all, how much time and effort has been spent discussing the fact that testing new small arms cartridges and getting the weapons to use them is seen as "too expensive."

Maybe things will be different now. I'm not holding my breath.
Maybe everything will magically get fixed just after the steel-cased Grendel ammo is delivered. (I know that was a cheap shot, as it were, but I could not resist!)

[BluntForceTrauma]

Stan, no, I do not think a green 6.5mm 108gr lead-free can compete with standard 7.62x54R PKM ball. We would have effectively handicapped ourselves.

Why not limit the top speed of our fighter jets in order to reduce carbon emissions and then wonder why we get blown out of the sky by the Su-35? Mucking Fidiots! Don't get me started. . . .

Nincomp, great point about long-range accuracy of a shoulder fired ABGL and ammo load. I think Joker also alluded to the problem with long distances and fine motor skills on the two-way range. But that's not a new problem, it's existed since the invention of the rifled bore. DMs and snipers train to overcome it. I remember reading that even in the days of musketry, new troops were counseled to fire at the feet of the approaching rank of enemy to counter the nervous tendency to fire too high.

And no amount of belted ammo load for your MGs is gonna overcome enemies hidden behind boulders. However they solve the problem of accurate rifle and MG fire at long range is the same set of skills needed to solve the problem of using ABGLs at long range. The beauty of an airburst grenade is that your accuracy problem is a matter of feet, even meters, instead of inches.

John

[stanc]

Stan, no, I do not think a green 6.5mm 108gr lead-free can compete with standard 7.62x54R PKM ball.

Well, there ya go, John. That's why Guardsman26 and others are thinking that the caliber of a GPC (with a LF bullet) will probably have to be 6.86mm.

But, I'd still like to see applicable testing done on this and other aspects of performance.

Nincomp, great point about long-range accuracy of a shoulder fired ABGL and ammo load. I think Joker also alluded to the problem with long distances and fine motor skills on the two-way range. But that's not a new problem, it's existed since the invention of the rifled bore. DMs and snipers train to overcome it.

And no amount of belted ammo load for your MGs is gonna overcome enemies hidden behind boulders. However they solve the problem of accurate rifle and MG fire at long range is the same set of skills needed to solve the problem of using ABGLs at long range. The beauty of an airburst grenade is that your accuracy problem is a matter of feet, even meters, instead of inches.

John, I agree with all of that. Question is, can a 40mm ABGL be made that is light enough for one man to carry and operate, and has a max effective range of 800 meters against point targets, yet has tolerable felt recoil?

[BluntForceTrauma]

Caliber doesn't matter — 6.8, 6.5, 6.35, 7, whatever — it's the performance that counts. That's why Bill Alexander hasn't really gotten into all this, hasn't developed military loadings, hasn't developed a 65G LMG, because the military procurement still has its head up its, uh, hinder. . . . They still need to figure out what it is they want. And even THAT'S no guarantee. They'll spend a zillion dollars on a program and STILL say, "Naw, guess we're gonna go a different direction."

So, yes, if they decide they want to match 7.62x54R ball with an intermediate lead-free projectile, it's a simple matter of bullet design and case capacity. Then we'll see if the result is acceptable in all the other pertinent parameters.

Regarding, the ABGL, you make a high-velocity 40mm by making it recoilless. That's why I suggested a "mini" Carl Gustav-type technology that would look similar to a Russian RPG launcher, except the grenade cartridges would be loaded internally, like a bolt-action.

You put the electronics in a sleek nose cone for a higher BC. Have long fold-down bipod legs, almost like "shooting sticks," for stability.

John

[stanc]

Caliber doesn't matter — 6.8, 6.5, 6.35, 7, whatever — it's the performance that counts.

I totally agree with that.

Regarding, the ABGL, you make a high-velocity 40mm by making it recoilless. That's why I suggested a "mini" Carl Gustav-type technology that would look similar to a Russian RPG launcher, except the grenade cartridges would be loaded internally, like a bolt-action.

You put the electronics in a sleek nose cone for a higher BC.

I've often wondered what ballistic improvement would result by putting a long, streamlined ogive on the 40mm grenade.

FWIW: 20mm Carl Gustav

http://www.youtube.com/watch?v=dUoBb3h9HWA

[stanc]

...why Bill Alexander hasn't really gotten into all this, hasn't developed military loadings, hasn't developed a 65G LMG...

So, yes, if they decide they want to match 7.62x54R ball with an intermediate lead-free projectile, it's a simple matter of bullet design and case capacity. Then we'll see if the result is acceptable in all the other pertinent parameters.

I find it quite understandable that Alexander hasn't developed a Grendel LMG. There's just too little chance for AA to make a profit from such a venture.

It's just that, after a decade of endlessly discussing nothing but theory, I'd really like to see some testing done to show how performance of a 65G LMG compares to the PKM (and other machine guns) in reality. Or, if not a 65G belt-fed, at least an M27-type automatic rifle.

[Tony Williams]

Stan, no, I do not think a green 6.5mm 108gr lead-free can compete with standard 7.62x54R PKM ball.

I'm not so sure. A green bullet is certainly unhelpful and 6.8mm may be a better choice, but 6.5mm should still work. I ran some data through the JBM calculator to compare the ballistics of 6.5 mm 8g/123 grain (lead core) and 7g/108 grain (green) bullet with the 7.62mm M80, assuming that both bullets' form factor would be the same as that of the 5.45mm 7N6 (.929 for the G7 FF, according to the BRL), therefore resulting in G7 BCs of .271 and .237 respectively. Some of the graphs below from this article illustrate how these compare (with 5.56mm M855 thrown in for fun):









The 6.5mm cartridge which I assumed in the above is a tad bigger than the Grendel, stretched to c.45mm.

[nincomp]

Another indication that a lighter bullet does not necessarily ruin the performance of the Grendel is that Arne Brennan used the 108 grain Lapua Scenar in long range competition. Now I know that a mass-produced military round will not have as high a BC as the 108 Scenar match bullet, but then again, neither would they match the 123 grain version which is sometimes used to demonstrate the Grendel's long range capability.

[stanc]

I'm not so sure. A green bullet is certainly unhelpful and 6.8mm may be a better choice, but 6.5mm should still work. I ran some data through the JBM calculator to compare the ballistics of 6.5 mm 8g/123 grain (lead core) and 7g/108 grain (green) bullet with the 7.62mm M80, assuming that both bullets' form factor would be the same as that of the 5.45mm 7N6 (.929 for the G7 FF, according to the BRL), therefore resulting in G7 BCs of .271 and .237 respectively. Some of the graphs below from this article illustrate how these compare (with 5.56mm M855 thrown in for fun):

<deleted>

The 6.5mm cartridge which I assumed in the above is a tad bigger than the Grendel, stretched to c.45mm.

Your comparative graphs are not only for a more powerful cartridge, you've also assumed a 20" barrel length for all calibers. The first assumption is obviously not applicable to 6.5 Grendel, and the second does not apply to a "Grendelized" M4 carbine, M27 IAR, and M249 LMG.

The question is what performance would 6.5 Grendel deliver with a 7g/108gr bullet, when fired from probable barrel lengths of 14-18 inches? Would a 65G M249 with 14" or 18" barrel come even close to matching M80 performance from the 20" barrel Mk48?

[LRRPF52]

This is why I say to base the performance match or over match on 7.62x54R out of the PKM, which has a 25.4" barrel, as well as the SVD with 24.4" barrel, and the SVDS with 23" barrel.