New Cartridge Developments and Implications for Dismounted Infantry Soldiers

[JASmith]

Be careful about how far you are willing to compromise the design to map-in to existing performance, policy, facilities, equipment and manufacturing equipment.

The clear conclusion when one errs in that direction is that the 5.56 and 7.62 NATO cartridges are just fine thank you!

We must first posit a genuine improvement, followed by rational tests if there is to be any hope of getting a change.

Please allow folks explore options that genuinely improve performance in the desired areas and to make reasonable trades in less important areas.

[stanc]

Be careful about how far you are willing to compromise the design to map-in to existing performance, policy, facilities, equipment and manufacturing equipment.

The clear conclusion when one errs in that direction is that the 5.56 and 7.62 NATO cartridges are just fine thank you!

Actually, 5.56 and 7.62 NATO are pretty darn good choices for a two-caliber system. Whether they can be improved upon enough to make a change worthwhile has yet to be demonstrated. So far, all we have are some theoretical ideas, with little or no test data to support them.

We must first posit a genuine improvement, followed by rational tests if there is to be any hope of getting a change.

I absolutely concur.

Please allow folks explore options that genuinely improve performance in the desired areas and to make reasonable trades in less important areas.

Hey, I'm all for exploring options. I just think that in addition to said folks exploring the good aspects of their ideas, it's also necessary to explore the bad and the ugly. Certainly if such proposals are presented to the military, you can bet that they will consider the drawbacks as well as the advantages.

[stanc]

Guess what -- a couple of the 6.8 guys are joining the party!

http://68forums.com/forums/showthread.php?22193-6.86x46-BRT

[BluntForceTrauma]

Guess what -- a couple of the 6.8 guys are joining the party!

Stan, it's "the ballistics, stupid!" I find it amusing that when the 6.8 guys have moments of honesty and clarity, such as Clint's proposal for a 6.8x46 and Cris "6.8 Designer" Murray's proposal for a 7x46, they advocate the very principles that define the 65G's genius: moderate velocity and high BC bullets. Imitation is the sincerest form of flattery and I'm glad to see these guys are coming around. Of course, they can't admit the 65G was right all along, so they up the case size and powder charge and teeter off the well-balanced "sweet spot" represented by the 65G and fall into a new generation of heavier-yet-again weapons and increased recoil.

Of course, in a perfect world it would be nice to launch ever heavier bullets with better BCs at ever faster velocities. Might as well propose the existing Lapua 6.5x47. But where does the weapon size and recoil spiral end?

Goldilocks summed it up: 6.5 Grendel is just right.

John

[LRRPF52]

Gents,

I think an important thing to remember is that the folks behind 6.8 SPC and 6.5 Grendel are on the same team in the big picture, while there are two different platforms on the market to offer a different set of ballistic capabilities from within the AR receiver/magazine platform.

When the 6.8 SPC was being developed, there was a constant reference to equipping M4's with something with more similarity to the 7.62x39 without losing 300-500m trajectory of the 5.56, and without the 7.62x39's magazine size/shape handicaps. I think the 6.8 SPC achieved exactly that.

The Grendel wasn't conceived under the idea of combining certain cartridge performances, but maximizing performance across the board from within the constraints of an AR15 platform. I think it has done exactly that, especially when you look at how close it is to .308 in terms of trajectory and wind deflection. I think if the guys from 5th SFG and AMU had been collaborating with Arne and Bill, maybe the 6.8 SPC might not have ever been conceived, and there wouldn't be these two dogs in the fight.

Once the totality of problem-solving, R&D, prototyping, testing, limited fielding in the civilian sector, and other efforts had been made, people were committed and dedicated to seeing their product through, which is a commendable example of ingenuity and follow-through in our private sector. It's very difficult for successful people to accept that there is a superior design that offers the capabilities of theirs and more, especially once their resources and time have been invested wholeheartedly into their creation.

With the other potentially-revolutionary concepts being tested right now, it will be very interesting to see what cartridges go the way of the gun, and what soldiers on into the 21st Century, especially if the LSAT gains traction.

[stanc]

Gents, I think an important thing to remember is that the folks behind 6.8 SPC and 6.5 Grendel are on the same team in the big picture...

Well said. You're quite right, of course.

...while there are two different platforms on the market to offer a different set of ballistic capabilities from within the AR receiver/magazine platform.

When the 6.8 SPC was being developed, there was a constant reference to equipping M4's with something with more similarity to the 7.62x39 without losing 300-500m trajectory of the 5.56, and without the 7.62x39's magazine size/shape handicaps. I think the 6.8 SPC achieved exactly that.

Very true. Even the underpowered loads from Remington deliver flatter trajectory than that of 7.62x39, and SPC II ammo provides a significant overmatch.

The Grendel wasn't conceived under the idea of combining certain cartridge performances, but maximizing performance across the board from within the constraints of an AR15 platform. I think it has done exactly that, especially when you look at how close it is to .308 in terms of trajectory and wind deflection.

Concur.

I think if the guys from 5th SFG and AMU had been collaborating with Arne and Bill, maybe the 6.8 SPC might not have ever been conceived...

And maybe the 6.5 Grendel would also have been aborted. The cartridge resulting from such a collaboration might well have been a cross between 6.8 SPC and 6.5 Grendel.

I've sometimes wondered what would result if the SPC's smaller case diameter and higher chamber pressure were to be combined with the Grendel's high-BC bullet @ moderate velocity concept.

[Tony Williams]

I think that both the 6.8mm SPC and 6.5mm Grendel were very good attempts to squeeze the maximum out of the constraints of the AR-15 package; they just have slightly different pros and cons.

The problem as I see it is the AR-15: the action is too short to accommodate the optimum compromise military round.

[BluntForceTrauma]

The way I look at it is that the 6.5 Grendel represents the upper range of the amount of recoil I'd allow for a general-purpose infantry rifle for average recruits. More powder, heavier bullets gets one something, of course, but that increase in capability must be tempered by usability. For example, we all agree full-auto 7.62 NATO is largely unusable for most troops. So, we must go smaller, and how much smaller is a matter of conjecture. I suppose the recoil of a heavier cartridge could be mitigated by newer recoil-management technologies, such as "constant recoil" (which I strenuously advocate).

I really think that for the something like 90% of engagements under 300 meters (averaging all the conflicts of the past 100 years) the 6.5 Grendel is perfectly reasonable, and how felicitous that its long-range trajectory, for the other 10%, is very comfortably within the parameters set by existing cartridges that have served us so well for many years.

The constraints of the existing AR magazine were serendipitous. It forced the development of a cartridge that maximized performance in a quite compact cartridge. By happy accident of those constraints, it's my opinion that an optimum cartridge was developed, even had we the benefit of a blank slate and unlimited resources. The trick never was getting superior performance from a larger case size, it was getting superior performance from a smaller case size.

I want a 6.5 Grendel with a 110gr T3 steel-tipped projectile (analogous to M855A1) for all man-portable infantry weapons. Much to LRRPF52's chagrin, this combines an LMG and an MMG into one weapon. (Try, perhaps, a scaled down MG42, akin to the Spanish CETME Ameli. The design is supposedly fundamentally sound and very reliable, although the mass-produced versions were fraught with jamming). For vehicle-borne weapons, when an M2 .50 cal. is too much, we need a .338 Lapua Magnum-class GPMG.

For the large majority of situations, I don't see what humping a 7.62 GPMG is gonna do that a 65G MG can't do. Neither is gonna be optimal for chewing through adobe walls. And without shot placement, neither, in my opinion, is gonna be deadlier than the other in soft tissue. In terms of pure capability, the 7.62N is probably "better," but in the bigger picture and in light of the slight overlap in capability the 65G provides, the weight and bulk of this capability is unnecessary for a man-portable weapon.

Of course, I largely defer to LRRPF52's military experience and his obviously thorough musings on the subject to shoot down my ravings, the wet dreams of a complete amateur civvie military buff. My opinions make rock-solid sense to me at this point, but I try to hold them humbly, and offer them to, perhaps, a new audience as food for thought.

John

[stanc]

The way I look at it is that the 6.5 Grendel represents the upper range of the amount of recoil I'd allow for a general-purpose infantry rifle for average recruits.

There's something to be said for that idea. Less felt recoil generally translates to better marksmanship.

More powder, heavier bullets gets one something, of course, but that increase in capability must be tempered by usability. For example, we all agree full-auto 7.62 NATO is largely unusable for most troops.

Granted, but these days the SOP even for 5.56mm is to use aimed, semi-auto fire almost exclusively. AFAIK, full-auto is rarely employed with 5.56 carbines and rifles, so controllability in automatic fire isn't something to be very concerned about.

I want a 6.5 Grendel with a 110gr T3 steel-tipped projectile (analogous to M855A1) for all man-portable infantry weapons. Much to LRRPF52's chagrin, this combines an LMG and an MMG into one weapon.

The only problem I see with that idea is you're assuming that belt feed of 6.5 Grendel is doable, something that has not yet been demonstrated.

[stanc]

P.S. Regarding your hoped-for 110gr T3, we should be able to get an idea of performance relative to 7.62 NATO by comparison testing M80 Ball and the Wolf 110gr FMJ...if/when it ever gets here, that is.

[Tony Williams]

Granted, but these days the SOP even for 5.56mm is to use aimed, semi-auto fire almost exclusively. AFAIK, full-auto is rarely employed with 5.56 carbines and rifles, so controllability in automatic fire isn't something to be very concerned about.

And yet - the first two US Army improvements due to be made to the M4 are a full-auto switch and a heavier barrel to withstand higher-intensity automatic fire. Something doesn't add up...

[Tony Williams]

P.S. Regarding your hoped-for 110gr T3, we should be able to get an idea of performance relative to 7.62 NATO by comparison testing M80 Ball and the Wolf 110gr FMJ...if/when it ever gets here, that is.

The problem is not how lead-cored FMJs compare, its how copper+steel bullets compare (since that's clearly what the US Army wants). Obviously, these will be significantly longer than lead bullets of the same weight, and tracer versions will be longer still. This potentially causes problems in achieving high BCs in smaller calibres and cases (especially with the cannelures needed for MG use), because their excessive length uses up case capacity and might even be difficult to stabilise.

The main priority as far as I'm concerned is in matching the long-range performance of the 7.62mm M80 while delivering a substantial reduction in weight, since that is going to be the major selling point to the army. Having invested so much in the M855A1, and having touted its capabilities so much, the army is unlikely to take much notice of claims that a calibre bigger than 5.56mm would add terminal effectiveness - they don't think it's necessary. The only shortfall in 5.56mm performance they are likely to acknowledge is at long range (500-1000m).

[RangerRick]

And yet - the first two US Army improvements due to be made to the M4 are a full-auto switch and a heavier barrel to withstand higher-intensity automatic fire. Something doesn't add up...

Even without using auto guys have been having M-4s overheat in high intensity fire fights in Afghanistan. The Taiban have been trying to isolate and overrun small outposts and the guys end up firing continuously for an hour or more resulting in overheating and failure. Some of it is just inadequate lubrication, but heat plays a factor.

It's always been a problem with any sort of weapon. I was taught to urinate on the machine gun barrel if necessary to keep it going.

[RangerRick]

I really think that for the something like 90% of engagements under 300 meters (averaging all the conflicts of the past 100 years) the 6.5 Grendel is perfectly reasonable, and how felicitous that its long-range trajectory, for the other 10%, is very comfortably within the parameters set by existing cartridges that have served us so well for many years.


I want a 6.5 Grendel with a 110gr T3 steel-tipped projectile (analogous to M855A1) for all man-portable infantry weapons. Much to LRRPF52's chagrin, this combines an LMG and an MMG into one weapon.

For the large majority of situations, I don't see what humping a 7.62 GPMG is gonna do that a 65G MG can't do. Neither is gonna be optimal for chewing through adobe walls. And without shot placement, neither, in my opinion, is gonna be deadlier than the other in soft tissue. In terms of pure capability, the 7.62N is probably "better," but in the bigger picture and in light of the slight overlap in capability the 65G provides, the weight and bulk of this capability is unnecessary for a man-portable weapon.

John

Having someone drop a case of 7.62 ammo to you out of a chopper when you are carrying a 5.56, and vice versa really sucks. So having 1 caliber for belt fed guns and rifles would really be great. Your troops could carry extra belts for the machine guns and break them down and load them in magazines in a pinch. The SAW's can even use magazines in a pinch, even though they have not been very reliable fired that way. But that is better than an M-249 club to beat them over the head with.

With a 6.5 platoon machine gun (Think SAW with a heavier, longer quick change barrel, and a pintle mount for the tripod) you could increase the muzzle velocity of the same round and get a flatter trajectory for grazing fire while still drastically reducing the machine gun system's total weight allowing more ammo to be carried. You could use the existing tripod and T&E mechanism, although a lighter one would be possible.

I know it really sucks for a grunt to have to carry machine gun ammo he can't use. Getting it passed, or carried to the machine gun in the middle of a fight is tough. If the gunners knew they could grab a belt off of nearly any grunt when they got low, it would be a lot more flexible.

As a leader you don't have to remember if Private Schmedlap is carrying a belt for the 249 or the 240. If he has a belt, that's all that matters.

Then if Private Schmedlap's chopper gets shot down and he's defending the crash site, he can break down the belts and load his magazines, and he knows what he is carrying will fire in whatever he can drag out of the wreckage that still works.

There's huge value in that.

RR

[stanc]

The problem is not how lead-cored FMJs compare, its how copper+steel bullets compare...

Of course. I suggested comparing FMJ only to see relative performance, since copper+steel bullets for both 6.5 and 7.62 likely won't be available to test for quite some time.