Future medium support weapon

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Subject: Future medium support weapon
Jeff_F_F 11/8/2007 7:25:30 PM

To avoid derailing any other threads, and because I'm realizing that Dogtag and I may have more in common concept wise than I'd thought previously... Here is my version of his concept: The background for this idea is projecting a decade in the future, and assuming that a OCSW 25mm light cannon/grenade machinegun is up and running as a heavy support weapon, and that our primary infantry weapons are the LSAT family firing telescoping rounds, either composite cased or caseless. At present this family of small arms is envisioned as using the the 5.56mm round, and some pictures suggest that perhaps an elongated, high BC version with significantly better performance at range is being considered. But what if instead the weapon used the 129grain bullet and powder charge from the 6.5mm Grendel for similar recoil at a lower muzzle velocity compared to the 5.56mm, but better long range performance due to the heavier round--just a bit lighter than the 7.62mm NATO, and with at least the long range performance of that round? Since entirely new weapons and ammunition are being envisioned anyway, there is no logistic penalty to the move and the weight difference would be minor. The 5.56mm ammunition is doing significantly better in the weight reduction department than the program requirements anyway. The SAW version of that weapon family would then have performance similar to the M240 in a much lighter and more mobile package, and with extremely light weight ammunition. What would be the logical replacement for the M240? A medium machingun using a larger caliber round such as 8.6mm--probably in either a round similar to the LSAT: either cased telescoping or caseless? Maybe so. Another option would be a weapon using the 25mm round that is intermediate in weight and firepower between the semi-automatic XM-25 and the Fully automatic OCSW. Perhaps using selective fire between semiautomatic and burst? While firing fewer rounds than M240, a burst of airbursting rounts would be quite effective at suppressing area targets, and single shots would give good capability against point targets including those in defilade.

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WarNerd My 2¢ 11/9/2007 1:09:32 AM

It appears that the value most desired in automatic support weapons is the psychological effect of suppressing fire. Basically, you want something that will throw a lot of bullets fair quickly to make the enemy keep his head down while the rest of the squad maneuvers for the kill. This argues for the machinegun over the autogrenade launcher.

It also does not seem likely that an intermediate weapon between XM-25 and the OCSW is of value. The OCSW is already manportable by a 2 man team, and without a second man hauling a tripod to absorb the recoil a burst capable XM-25 would be too inaccurate to be of value.

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doggtag I will get involved in this at some point today... 11/9/2007 8:42:20 AM

...and yes, Jeff, you're on the same track I was thinking (or at least running parallel enough to it).

Hectic day coming, so I'll have to wait until home time this evening to get back to you, both on this and the long long reply from the 8.6mm thread (but I'll try dragging it over here), where I can elaborate further..

Thx.

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Horsesoldier 11/9/2007 1:00:55 PM

But what if instead the weapon used the 129grain bullet and powder charge from the 6.5mm Grendel for similar recoil at a lower muzzle velocity compared to the 5.56mm, but better long range performance due to the heavier round--just a bit lighter than the 7.62mm NATO, and with at least the long range performance of that round? Since entirely new weapons and ammunition are being envisioned anyway, there is no logistic penalty to the move and the weight difference would be minor. The 5.56mm ammunition is doing significantly better in the weight reduction department than the program requirements anyway.

129 grain bullet versus a 62 grain bullet or even a 90 grain bullet wouldn't be without a logistical penalty, as it's simply going to weigh more (and be somewhat more bulky due to cartridge dimensions), which means more cargo aircraft sorties or helicopter sorties or truck convoys or whatever to haul it around. The penalty probably would not amount to much at the individual soldier's basic load level, but the bigger the picture level the more $$$ it would entail, particularly if you're talking about the high ballistic coefficient target rounds that Alexander Arms likes to hold up next to standard ball ammo in other caliber to "demonstrate" Grendel's superiority (as these would add to your overall cost per round, but without them you don't get your almost-MMG performance out of Grendel, as it's nothing fancy when loaded with something less than Lapua's best target ammunition).

Now, if the heavier round has strengths that offset the minuses, like, say better barrier penetration (which you get from a 6.5mm, heavier bullet), or better terminal ballistics (which you don't get with the high BC loads for the Grendel, as they are slower to tumble or fragment than 5.56mm and 6.8 Rem SPC, slower to tumble than 7.62 M80 ball, etc), the benefits may offset the liabilities. The best argument, I think, is the one you touch on -- the potential to get a workable assault rifle round that gives you almost a medium machinegun round at the same time. Reducing small arms calibers organic to an infantry platoon down to one (or two, if they issue everyone a pistol like they should) has merits, logistically speaking, that I think would offset increased weight per round.

What would be the logical replacement for the M240? A medium machingun using a larger caliber round such as 8.6mm--probably in either a round similar to the LSAT: either cased telescoping or caseless? Maybe so.

I'm not sure there'd be a logical reason to field such if you have a 6.5mm "heavy intermediate" assault rifle round in service. I'd guess that a sustained fire kit for the SAW/LMG 6.5mm weapon would be adequate to do a MMG's mission, without re-introducing the two caliber logistical dilemma your 6.5mm round initially solved. Above that, you have .50 cal, 25mm (OCSW or Bradley), etc etc etc.

Another option would be a weapon using the 25mm round that is intermediate in weight and firepower between the semi-automatic XM-25 and the Fully automatic OCSW. Perhaps using selective fire between semiautomatic and burst? While firing fewer rounds than M240, a burst of airbursting rounts would be quite effective at suppressing area targets, and single shots would give good capability against point targets including those in defilade.

My guess would be that, again, this would add a level of complexity the big picture types would not support, when there will already, hypothetically, be two flavors of 25mm ammunition in the system. My guess is there would not be a perceived niche between the XM25 and OCSW to fill, even if you used XM25 ammunition for that role to avoid overcomplicating the supply issue.

On the topic of burst versus automatic, I'm also not sure there's much need when you're talking about something in 25mm caliber -- rate of fire in automatic would be sufficiently low (to allow for any degree of accuracy by the operator) that a three round burst would be easy to do. I seem to recall (and may be mistaken) that OCSW is supposed to 240-250 rpm, which is easy to count rounds out.

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doggtag 11/9/2007 7:59:31 PM

Without cutting and pasting a full book's worth of previous posts (both of here and on the 8.6 sniper thread (for the record, we'll clarify that 8.6mm isn't a typo of 6.8mm and actually does refer to the .338 caliber cartridge, for those new to this thread),

I'll try and lay out what I was talking about.

I'll not go into the 5.56mm vs calibers X, Y, and Z debating, as it's gotten long and tiresome and there are more than enough arguments from both sides (for/against) to keep it lasting well into the next century (all those Strategy Page what-if threads a century from now as to why we made the military decisions we'll make over the next decade or so...).

On the note of a new caliber for a medium machine gun (and precision long range rifle),

and this is assuming the 5.56 at some point does get replaced by an intermediate cartridge offering near-7.62 performances (take down power at range and preferrably a low dispersion) but without the full weight/logistics penalities of 7.62mm weapons and ammo yet overcomes all the voiced deficiencies and other concerns of 5.56mm weapons,

and it's assuming the ACSW Advanced Crew Served Weapon (OSCW's new moniker) becomes the preferred heavy machine gun (ideally in a CROWS type mount dual-feeding, from either side, so both airburst and anti material rounds are available at the flip of a switch...we may even see vehicles mount the Bushmaster LW25 in a more permanent mounting, instead of the ACSW which can be crew-removed and used off a ground mount),

I'm pondering if 12.7mm may actually, after a full century's use, find itself falling out of favor.

Weight wise, 12.7mm weapons, both HMGs and sniper/anti material rifles, are notoriously heavy.

The HMG needs a vehicle for transport or breaks down into, what, 3 or 4 manpack loads, not to mention ammo boxes?

Whereas the rifle versions are minimally a two-man team operation.

Ditto to any current and projected 25mm converts, "Payload Rifles" as Barrett likes to call theirs.

So if 25mm class heavy MGs gain favor, and a replacement small arms caliber is chosen,

will we need a new caliber to fill the void left between the new small arms caliber (adequate enough to replace 7.62 as well as 5.56) and the grenade/heavy machine gun?

Will the 12.7mm end up under scrutiny like 5.56 is now, as more and more developers create new cartridges and bullet designs?

(or would it be more akin to back in the day when 7.62 was deemed overkill and something a tad lighter and easier on recoil was desired, thus giving us 5.56?)

So something between 7.62 and 12.7 may eventually find more favor: lower logistical footprint (both the ammo and the weapons using it) than anything of actual 12.7mm class, but more controllability and transportability issues, as well as slightly friendlier logistics footprint, closer to 7.62mm class weapons.

So this new caliber thus will be something falling between the .338 (increasingly popular Lapua) and the .416 (newer Barrett expirement).

Will we just settle on the .338?

Or will something a bit more "aggressive" be needed, in the form of a near-12.7mm-performance round but in a slightly smaller package?

It's a fair bet that continued tinkering with these midrange cartridges and bullets will yield improved perfomances (both in ball/anti personnel rounds as well as AP/anti materiel rounds), just as the most recent 5.56 and 7.62 ammo is much better than the original rounds of those calibers.

So suggesting near-12.7mm performance from a slightly smaller package isn't out of the question.

European types would suggest, "why not settle for an even 10mm design?"

US types might suggest, "we're not using metrics just to make math easier for you, so we want .375-ish (we still like using our inches)."

(Again, this is speculation around the fact that someone finally creates the ~~perfect~~ most ideal go-between cartridge/bullet combo that offers near-7.62 performance at closer-to-5.56 logistics footprint...)

It's agreed we don't need to create a machine gun intentionally built around match grade ammo.

But when we get into discussions of downrange dispersal patterns and beaten zones and hosing a target's general area,

this is where I play the precision fires card.

The ~~OCSW~~ ACSW (M307 in 25mm, or M312 in 12.7mm) was designed with a lower rate of fire (250-ish), either as 12.7mm or 25mm, than other HMGs (400+ like in the venerable M2).

And yes, at that lower rate, the gunner can count r

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Horsesoldier 11/10/2007 11:16:39 AM

So this new caliber thus will be something falling between the .338 (increasingly popular Lapua) and the .416 (newer Barrett expirement).

Will we just settle on the .338?

I am not sure you'd see much weight savings at the upper end of your possible calibers. Ammo for the .50 cal ranges from the low 600s to just over 700 grains (for the projectile by itself), excepting the SLAP stuff. The Raufoss/Mk 211stuff is about middle of the pack at 670 grains. The Barrett .416 round is 400 grains -- but that's a lathe turned match solid brass round. If loaded with a lead or lead/tungsten, copper jacketed FMJ kind of round it's probably somewhere in the 550 grain range. You'd get something similar with the 408 Chey-Tac, which is shooting 3-400 grain projectiles, but again they're lathe turned copper/nickel alloy, not military FMJ ammo.

So you're looking at a bit of savings on ammunition weight (I'm only considering bullet mass on the assumption we're talking about some new caseless or CTA cartridge in any case). You may get a bit of a savings on receiver mass and such, as the 416 and 408 rounds are not as powerful as the .50 cal, but you're still talking about something that is going on a vehicle or only man portable as a group load, and less kinetic energy is less kinetic energy when push comes to shove. Less power means less barrier penetration, less impressive terminal ballistics, and, essentially a less effective heavy machinegun.

I'd offer there's a reason that all the replacements for .50 cal tried in the last few decades for heavy machineguns have all looked at going higher caliber and more muzzle energy. The interest in things like 408 Chey-Tac are for man portable sniping weapons and so have a very different set of requirements and needs they are addressing.

At the other end of the spectrum with .338, I'm still wondering what it brings to the table if you have a standard rifle round that is almost MMG performance and your platoon level support weapon is firing 25mm smart shells. Like I said in the other thread, one of the better arguments I can see for a round heavier than 5.56mm is the possibility of an entire caliber of ammunition from a unit's logistical requirements. Going heavier than 5.56mm in a rifle is going to have drawbacks as well as any benefits -- smaller basic load of ammo, slower handling due to higher recoil and such. Issues of terminal ballistics are a whole other discussion, but I'd note that the minuses of a heavier round may not be huge with a round in the 6.5 Grendel/6.8 Rem SPC range, but they're still there. But, being able to have a platoon's rifles/carbines, SAWs and LMGs all firing one caliber of ammunition is a big plus that justifies some reasonable (and modest) minuses on the rifle. Adding back in a whole other flavor of ammo with a new, somewhat heavier MMG cartridge begs the question of why accept any minuses on a rifle to make the SAW more LMG/MMG like when there is then an MMG available anyway.

If we're looking at a new machinegun cartridge as well, then there just doesn't seem to be much logic in sacrificing performance on the rifle, or spending extra on ammunition to make it better for engagements beyond 300 meters, when we could be optimizing rifle ammunition for use in a combat rifle and letting the 8.6mm MG or whatever be optimized for the MG role.

Or will something a bit more "aggressive" be needed, in the form of a near-12.7mm-performance round but in a slightly smaller package?

Mk 211 .50 cal is the wave of the future, I'd say, with a tungsten penetrator and HE and

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Nichevo Just throwing this out there... 11/16/2007 3:57:16 AM

The question of long range lethality, accuracy, etc. is one question. I like a cartridge in the .250-.280 range (6.5-7mm or so) over the existing choices - probably a fine hunting cart like the .270 Win would do the job nicely if we wanted to go back to a .30-06 length round (7.62x63mm). If you want a shorter OAL with such ballistics you need a fatter case. Caseless would of course help all this along.

However - on a different angle:

For CQB, the round of choice is now the 5.56 fired from the M4. This presents certain problems which we all know well. Point being: if you don;t worry about very long range shooting, but want to maximize stopping power/lethality,

how about a bigger slower bullet?

Somebody mocked the 10mm as Euro-inspired, but actually how about a straight-walled case around 10x40mm with OAL around that of the 5.56x45mm NATO? Bullets can be as big as you like - figure a velocity of at least 2000 fps out of a 10" barrel - at the beginning of hydrostatic effects, but meanwhile having SMASH, as Herald would say, far greater than a .223. (What is SMASH again? ;>)

Figure now the hot 10mm Auto is a 10x23mm cart and gives you, what, 1000fps with a 200gr pill. 1200fps with a 180gr? Out of a 5" barrel. From a 10" to 14" barrel and a much bigger case you should be able to break 2000fps easy - you get almost that with some of the hotter .41, .44 Mags. 2400fps maybe?

I favor caseless (who doesn't?) because in such a size the brass would be a considerable part of the weight. Even so, this would exceed lethality even of the 7.62 at close ranges.

Think roughly of the AK round necked up to .40 caliber. Or a 10mm Magnum. Controllable under full auto at a low cyclic.

If you wanted a subsonic loading for SOF, you could cram in one hell of a big bullet; you could almost shave down a .50 cal to .40; go putting what, 500gr pills at 1000fps into sleepy sentries and they'll stay asleep. Would probably extend range too.

But chiefly for ranges under 100m, I should think, though perhaps that is pessimistic. In any case it should do the job on Johnny Jihad with a veinful of epinephrine or PCP, coming to get his 70 raisins.

Let's just leave out the whole logistics thing if you don't mind, or at least don't dismiss on those grounds.

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Horsesoldier 11/16/2007 9:20:50 AM

how about a bigger slower bullet?

Somebody mocked the 10mm as Euro-inspired, but actually how about a straight-walled case around 10x40mm with OAL around that of the 5.56x45mm NATO? Bullets can be as big as you like - figure a velocity of at least 2000 fps out of a 10" barrel - at the beginning of hydrostatic effects, but meanwhile having SMASH, as Herald would say, far greater than a .223. (What is SMASH again? ;>)

Figure now the hot 10mm Auto is a 10x23mm cart and gives you, what, 1000fps with a 200gr pill. 1200fps with a 180gr? Out of a 5" barrel. From a 10" to 14" barrel and a much bigger case you should be able to break 2000fps easy - you get almost that with some of the hotter .41, .44 Mags. 2400fps maybe?

I see some issues with the idea. The first is that if you're talking about slinging a pistol sort of bullet downrange (even with a real hot load), you're getting pistol sort of ballistics on the receiving end, which are limited by the nature of the bullet. Slow to tumble, and such a short aspect ratio that when they do tumble it doesn't mean much. Thick, squat bullets preclude much chance of fragmentation in an FMJ format. The bigger hole is better, but I suspect you'd see much better terminal ballistics out of the same bullet weight in a smaller diameter (30 cal 200 grain as a point of comparison, for instance), while pushing a FMJ pistol bullet at those speeds just, ultimately, gives you a pistol bullet wound -- and complaints about FMJ pistol round lethality are as widespread, or more so, than complaints about 5.56mm (though I will note that most of the people complaining about pistol lethality have never used one in combat and have unrealistic expectations about pistol performance if they have).

Second, recoil is supposed to be based on momentum (mass * velocity) rather than kinetic energy. A 200 grain projectil at 2400 fps looks like it would actually have as much, possibly more, recoil than M80 ball 7.62mm ammo (146 grains at 2750 fps 78 feet from the muzzle). I think this load would be slower handling due to recoil than 7.62x51, much less 5.56mm or the proposed intermediate rounds.

Third, shooting a pistol bullet gives you pretty limited longer range ballistics when the CQB fight suddenly requires you to engage at 100-300 meters (like, say, moving through a building and seeing a bad guy down the street through a window).

I think overall it would kind of be a hybrid mix of the SMG and assault/battle rifle, with liabilities from the two. If it could be loaded with JHP ammo I think you'd have some solid lethality (particularly if the bullet design were optimized for the high velocities you're talking about), but in FMJ you're talking about one in-and-out wound channel twice the size of a 5.56mm bullet that does nothing -- no fragmenting, no tumbling. When the 5.56mm round does fragment (as it tends to do at CQB ranges) any sort of terminal ballistic advantage would be murkier.

Let's just leave out the whole logistics thing if you don't mind, or at least don't dismiss on those grounds.

I think it has problems besides the logistic angle, but it's worth noting that a 200 grain bullet weighs more than an entire loaded cartridge of 5.56mm M855 ammunition. Add in case, powder charge, and such, and you're looking at something I'd guess is heavier than 45 ACP weight (330 grains loaded), given a longer cartridge that's going to have pretty thick construction to deal with chamber pressure. That's going to be mean significantly less ammo carried as a basic load.

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Bigbro 11/16/2007 12:10:03 PM

The question of long range lethality, accuracy, etc. is one question. I like a cartridge in the .250-.280 range (6.5-7mm or so) over the existing choices - probably a fine hunting cart like the .270 Win would do the job nicely if we wanted to go back to a .30-06 length round (7.62x63mm). If you want a shorter OAL with such ballistics you need a fatter case. Caseless would of course help all this along.

The .284 winchester will work in AR10 and FAL actions. With a 300yd zero it will be about 280" low at 1000yds, M118 is about 360" low at the same range if I remember correctly. There is no savings in ammo weight.

For CQB, the round of choice is now the 5.56 fired from the M4. This presents certain problems which we all know well. Point being: if you don;t worry about very long range shooting, but want to maximize stopping power/lethality,

how about a bigger slower bullet?

Somebody mocked the 10mm as Euro-inspired, but actually how about a straight-walled case around 10x40mm with OAL around that of the 5.56x45mm NATO? Bullets can be as big as you like - figure a velocity of at least 2000 fps out of a 10" barrel - at the beginning of hydrostatic effects, but meanwhile having SMASH, as Herald would say, far greater than a .223. (What is SMASH again? ;>)

John Taylor used this to describe the difference in observed performance on African game animals in one of his books. MV X WT with a diameter factor. This was worked out for rounds that had velocities of about 2000 fps. What has to be taken into account is the amount of penetration needed on a target.

Figure now the hot 10mm Auto is a 10x23mm cart and gives you, what, 1000fps with a 200gr pill. 1200fps with a 180gr? Out of a 5" barrel. From a 10" to 14" barrel and a much bigger case you should be able to break 2000fps easy - you get almost that with some of the hotter .41, .44 Mags. 2400fps maybe?

Already done in a couple of forms, .458 SOCOM and the Russian 9.3 x 39 mm.

As for real world performance, a 44. mag rifle loaded hot bucks pretty good. I load mine with 270 gr bullets at about 1600 fps. This will shoot end for end through a large deer at 150 yds. The results are no better than a .257 Roberts with 117 gr. bullets in terms of a quick end to matters, it just over penetrates like crazy.
Bb

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Yimmy 11/16/2007 12:28:40 PM

I used to love this kind of debate, but to be honest now I think what currently exists does the job fine.

Large diameter bullets are a thing of the past in small arms. Wound ballistics is all about how long the round is, and how quickly you can get it to yaw and fragment. Short and fat bullets will not penetrate body armour by sheer energy on target alone. As the Box 'O Truth says, "pistols are pistols and rifles are rifles". 5.56mm is fine for rifles, and 7.62mm is fine for GPMG's. Most attrition on the battlefield is caused by support weapons and HE anyway.

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doggtag the whole problem going with caseless... 11/16/2007 1:15:03 PM

...is that we have to consider the environments and conditions which we're designing the round for:

-it has to survive temperature extremes from arctic to desert, easily peaking at -30º F (or more) to upwards of 140º F (stuff can get pretty hot sitting inside boxes and crates under a hot desert sun).

So this caseless design is going to have to cover amost a 200º temperature differential,

and without becoming brittle, or prone to cracking, or prone to degrading (corroding or rusting if highly metallic, or decaying if highly organic).

-it has to be able to endure not only freezing (and still function at that temperature), but also withstand environments of both fresh water (rain, swamps, waterways, etc)

and salt water (SEAL teams, Marines, USCG, USN applications).

-it has to be at least as shock resistant as cased ammo: sure, I can understand they'd be unsafe to use if chipped, cracked, dented, distorted, etc, just like regular cased ammunition.

But is it durable enough to survive the repeated abuse everyday grunts will subject it to, rattling around in magazines and ammo pouches, bumping magazines against objects and subjecting the rounds to repeated impacts?

And what if a stray round is rolling around in your pocket or ammo pouch?

Will it be safe to fire if it gets scraped or a minor chip?

We'll have to consider what constitutes a safe round to fire, and just how much loss of material we'll allow within a safety margin that will still have the round exit the barrel and not lodge only part way up.

(if a piece of propellant flakes off, as long as the igniter is still intact, how much combustible case being lost or damaged will we allow for before the round is considered unsafe?)

-what about cook-offs in a hot weapon?

Will we be able to fabricate a sufficient solid propellant material (or combustible case) that will withstand high heat without prematurely igniting, but is guaranteed to fire when the igniter functions as it should?

Seems we're getting better at making insensitive munitions (warheads) that don't detonate when exposed to fire,

but a round encased in intentionally-combustible propellant material will be a tough goal,

especially considering when we add in all the above features (water proof both to fresh and salt water, freeze proof and doesn't become too brittle for arctic environments, nor becomes too soft and pliable in hot and arid or hot and humid areas).

If it comes down to the point that we can only develop a caseless round (it will either be a solid propellant housed inside a hollow-tailed bullet, or a combustible case wrapped around it, telescopic most likely) that is only suitable for temperate zone combat, but we need different (cased) ammo for hot desert fighting or cold arctic warfare, how are we even saving any money then, having to procure ammo based on the temperature zone we're fighting in?

-Will the combustible material fully be consumed when ignited,

meaning, will it completely burn, or will it leave a high residue behind, even unburned grains?

(that could drastically compromise follow-on shots.)

These obstacles aren't tricky to overcome by themselves,

but in combination, that's the greatest hurdle,

which is why I expect that cased ammo will be around for a long time, at least as far as small arms are concerned.

(Yes, I'm aware that some tanks have tried using semi-combustible rounds, but again there are reliability issues, what with various temperature extremes, different moisture levels, and overall brittleness figured in.)

For the durability and reliability that cased ammo brings to the table, I believe it's going to be around for a long time.

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