New Army "Caliber Configuration Study"

[stanc]

It seems to me that if the Infantry has a 6.5mm LMG with a high BC projectile there will be no need to drag along the .338 MMG or any other MMG for that matter.

Quite possibly true. It sorta depends on the exact capabilities of the 6.5mm LMG, and mission requirements.

While the 50 cal can be deployed by dismounted squads, it's in no way practical, so why should we expect a .338 MMG to be implemented in this manner.

Because a .338 MMG would presumably be much, much lighter than a .50 HMG.

http://www.youtube.com/watch?v=JNB7khjOSXc

[stanc]

Depends on how you define GPC. At the moment the US Army has four rifle/MG cartridges used in the anti-personnel role: 5.56 x 45, 7.62 x 51, .300 Win Mag, .50 BMG. Only the first two are used in the standard rifles/MGs routinely carried by dismounted infantry; a single GPC could replace both of them in the organic squad weapons.

Not in my wildest dreams have I imagined the GPC also replacing the .300 Win Mag and the .50 BMG, even though such capabilities may occasionally be attached to squads for specific purposes.

Well, .50 Browning is in a completely different class than the other rounds, so I sure wouldn't consider it when defining a "General Purpose Cartridge" for use in man-carried weapons.

As I see it, a true "general purpose" round would be used as 7.62 NATO was originally intended to be: For the infantry rifle, automatic rifle, sniper rifle, and GPMG.

However, snipers have since gone beyond 7.62 NATO, to special purpose cartridges like .300 Win Mag and .338 Lapua. In addition, the automatic rifle has -- in most cases -- been replaced by the LMG, while the GPMG has become the MMG.

Now, the LDAM program seeks to replace 7.62 NATO for MMG use with a round that would necessarily be much bigger, heavier, and more powerful than the proposed GPC. That means infantry platoons would, as I said, still have two different calibers, just bigger and heavier than what they now use.

Since what you call a GPC would, at most, only replace a mix of calibers in the rifle squad, not at platoon and higher, a more accurate name would be Squad Common Cartridge (SCC).

Hey, I just realized that's also my initials!

Of all of the small arms western forces have faced recently, the PKM seems to have been the most problematic. The nearest western equivalent is the MK48. I can't see the US being happy to replace the MK48 with a weapon which could be outperformed by the PKM. Which implies that the GPC needs to be able to at least match the long-range hit probability of the big 7.62mm cartridges.

I don't know whether or not that is a goal of the CLAWS program, but for the sake of discussion I'll assume it is.

In that case, is it not possible to achieve that level of long-range hit probability with a Squad Common Cartridge which is smaller and lighter than the notional GPC?

[JASmith]

Much of the earlier debate in this general area centered on having the bullet have a specified kinetic energy at distance.

Have I missed something in the apparent shift to hit probability as being of very high performance? (I happen to agree with this.)

What are we asking the bullet to do when it gets there for CLAWS and LDAM?

[stanc]

The earlier focus on retained energy at long range was understandable when discussing a GPC that would replace both 5.56 and 7.62 NATO in infantry units. It seemed likely that for the military to buy into this concept, the notional GPC would have to provide external ballistics and terminal effects at least comparable to those of 7.62 NATO.

However, the introduction of the CLAWS and LDAM programs makes it clear that the US Army intends to keep a two-caliber system: "Caliber A" weapons replacing the 5.56mm carbine, rifle, and SAW, plus the 7.62mm DMR and LMG; "Caliber B" MMG replacing the 7.62mm MMG.

With an LDAM MMG (for example, something like the GD .338 LWMMG) providing much greater terminal effects than the 7.62 M240 MMG, it doesn't now seem to be essential to match 7.62 terminal effects with CLAWS weapons, but achieving comparable trajectory and drift would still be desirable.

Unfortunately, the only information that I've seen on CLAWS and LDAM is the very minimal data in post #2 of this thread, so I can't answer your last question.

[stanc]

Fight PKM with PKM?

Below: Polish UKM-2013, 7.62 NATO, 18.5 lbs.

[Tony Williams]

Well, .50 Browning is in a completely different class than the other rounds, so I sure wouldn't consider it when defining a "General Purpose Cartridge" for use in man-carried weapons.......

Now, the LDAM program seeks to replace 7.62 NATO for MMG use with a round that would necessarily be much bigger, heavier, and more powerful than the proposed GPC. That means infantry platoons would, as I said, still have two different calibers, just bigger and heavier than what they now use.....

Since what you call a GPC would, at most, only replace a mix of calibers in the rifle squad, not at platoon and higher, a more accurate name would be Squad Common Cartridge (SCC).

LDAM is apparently also supposed to replace the .50 BMG in infantry units, not just the 7.62mm, so I think it is relevant to include it. As I read it, it will not routinely be carried by dismounted infantry, but will be held back in the support role at platoon or company level, along with various other capabilities (which might include mortars, MANPADS, ATGW).

I suspect that your phrase "only replace a mix of calibers in the rifle squad" will probably include something like 90% of the rifles/MGs issued to infantry, so the "only" seems unjustified.

[Tony Williams]

Much of the earlier debate in this general area centered on having the bullet have a specified kinetic energy at distance.

Have I missed something in the apparent shift to hit probability as being of very high performance? (I happen to agree with this.)

What are we asking the bullet to do when it gets there for CLAWS and LDAM?

Good questions.

There has been a lot of debate in various forums (especially mine) concerning the performance requirements of a GPC. This has been complicated in recent years by the insistence of the US Army on lead-free ammunition. This is a particular problem for a GPC in which the bullets must already be long for their calibre in order to provide good performance at long range. Lead-free implies even longer bullets (which brings stability problems) or lighter ones (which reduces the ballistic coefficient).

My take on the GPC as it currently stands is that, if it is to replace the 7.62mm in light weapons, it is an absolute requirement that it at least matches the hit probability of the M80 out to long range (however that is defined, but I generally take this to be 1000m): which means in its trajectory, flight time and wind-bucking capabilities. I also still believe that the muzzle energy must be held down to c.2,500 J/1,850 ft/lbs in the interests of ammo weight and recoil.

The traditional approach to the GPC relies on a relatively heavy bullet (e.g. 6.5mm/120+ grains) with a significantly better BC than the M80, so that although it starts with less velocity it gradually catches up with the M80; first in terms of velocity, and subsequently in energy. This is clearly the optimum solution for the best long-range performance.

The probable need to use lighter lead-free bullets indicates that a slight shift in the specification may be appropriate. At the extreme, this could mean a bullet which has the same BC as the M80 and is fired at the same MV: this will, by definition, match the velocity and hit probability of the M80, but it will never match the energy. The bullet will probably weigh no more than 7g/108 grains (assuming 6.5mm calibre - there are of course other options), which will bring some benefit in ammo weight and recoil. This may be satisfactory if LDAM results in a lightweight .338 MMG which could be assigned to infantry patrols for long-range engagements.

My feeling, from following the various technical debates about bullet design, is that it is possible to achieve something of a compromise here: a light, lead-free bullet which has a better BC than the M80 and therefore still closes the energy gap as the range increases.

It is of course possible to match the hit probability of the M80 with other calibres than 6.5mm: but smaller calibres will inevitably widen the energy gap with M80, making it less likely that the Army would accept them as a 7.62mm substitute. After all, while the primary reason for the retention of 7.62mm is its longer effective range than 5.56mm, the fact that it hits considerably harder at all ranges is also valued.

So, to sum up: matching the long-range hit probability of M80 is essential; matching or at least approaching its long-range impact energy is desirable (but not essential, especially if a .338 MMG is adopted). The optimum specification will of course depend very much on what can be achieved with the bullet design; the higher the BC, the easier the task becomes and the more options are available.

[JASmith]

Tony,

Thanks!

This helps put things in perspective.

Cheers!

[stanc]

As I read it, [LDAM] will not routinely be carried by dismounted infantry, but will be held back in the support role at platoon or company level...

On what do you base that? The info from Guardsman26 says nothing to that effect.

BTW, how often do rifle squads operate independently from the platoon?

I suspect that your phrase "only replace a mix of calibers in the rifle squad" will probably include something like 90% of the rifles/MGs issued to infantry, so the "only" seems unjustified.

Well, your "GPC" would provide a common cartridge only for the rifle squad, not the platoon, company, or battalion, right?

Seems to me that makes it a Squad Common Cartridge, not a General Purpose Cartridge.

[JDub]

How about a round that is something with slightly more case capacity than our beloved grendel in 6.5 (of course) for full power applications and sabot round for cqb?

The DMR and LMG applications will benefit from reduced weight and recoil vs. 7.62x51. The sabot round could also have a high bc and enough velocity to reach out to 600+ yards without much more recoil/impulse than 5.56(something along the lines of the mk262) so door kickers aren't hosed if they happen to need to engage targets at 300+ yds.

So full power rounds would be 120-140gr @ 2600-2700fps and cqb maybe 70-80gr@2700-2900fps and the barrels are 1:8. Just ballpark.

Is small-arms sabot technology mature enough for military applications? Do you think this concept has any merits?

Additionally, the sabots can be made of frangible bamboo so there is the possibility of giving the enemy some nasty splinters.

[Tony Williams]

On what do you base that? The info from Guardsman26 says nothing to that effect.

LDAM is supposed to replace .50 BMG in the anti-personnel role, which means it will be using ammo significantly bigger and heavier than 7.62mm. Also remember that before Afghanistan, 7.62mm MGs were not carried by infantry squads (in fact, the British Army is reportedly considering pulling them back into a support role, leaving the section with nothing but 5.56mm).

BA excepted, an increasing number of armies seem to be looking for lightweight 7.62mm MGs at section level, while keeping the heavy 7.62mms back in the support role. I envisage CLAWS - and the GPC - replacing all of the 5.56mm weapons and also the lightweight 7.62mm MGs and DMRs. LDAM would replace the heavy 7.62mm and the .50 cals in the support role.

Well, your "GPC" would provide a common cartridge only for the rifle squad, not the platoon, company, or battalion, right?

It would provide a common cartridge for all soldiers with rifles (except snipers), and for all soldiers carrying portable MGs, leaving only the heavier support weapons in a significantly larger calibre.

Seems to me that makes it a Squad Common Cartridge, not a General Purpose Cartridge.

Seems to me it doesn't...

[Tony Williams]

How about a round that is something with slightly more case capacity than our beloved grendel in 6.5 (of course) for full power applications and sabot round for cqb?

Sabot rounds may be needed in due course, to deal with enemy troops wearing modern body armour. They would not be the obvious choice for short-rage work otherwise, since they are unlikely to deliver the same terminal effectiveness as full-calibre bullets. And at short range, you need your enemy out of the fight as quickly as possible.

[stanc]

LDAM is supposed to replace .50 BMG in the anti-personnel role...

That is not what Guardsman26 said: "[LDAM is] envisioned to replace the Medium Machine Gun and possibly the HMG (.50 BMG)."

Also remember that before Afghanistan, 7.62mm MGs were not carried by infantry squads...

So what. Pre-Afghanistan is no longer relevant.

I envisage CLAWS - and the GPC - replacing all of the 5.56mm weapons and also the lightweight 7.62mm MGs and DMRs. LDAM would replace the heavy 7.62mm and the .50 cals in the support role.

Yes, that's mostly the same as what Guardsman26 reported the US Army envisions for CLAWS and LDAM (except for the uncertainty of LDAM replacing the .50 HMG).

It would provide a common cartridge for all soldiers with rifles (except snipers), and for all soldiers carrying portable MGs...

That's evading the point. The notional GPC does not provide a common cartridge for the weapons squad, infantry platoon, company, and battalion.

And since when isn't the .338 LWMMG a portable machine gun?

[LRRPF52]

LDAM is supposed to replace .50 BMG in the anti-personnel role, which means it will be using ammo significantly bigger and heavier than 7.62mm. Also remember that before Afghanistan, 7.62mm MGs were not carried by infantry squads (in fact, the British Army is reportedly considering pulling them back into a support role, leaving the section with nothing but 5.56mm).

BA excepted, an increasing number of armies seem to be looking for lightweight 7.62mm MGs at section level, while keeping the heavy 7.62mms back in the support role. I envisage CLAWS - and the GPC - replacing all of the 5.56mm weapons and also the lightweight 7.62mm MGs and DMRs. LDAM would replace the heavy 7.62mm and the .50 cals in the support role.



It would provide a common cartridge for all soldiers with rifles (except snipers), and for all soldiers carrying portable MGs, leaving only the heavier support weapons in a significantly larger calibre.



Seems to me it doesn't...

In the US Army Infantry, 7.62 NATO Medium Machine Guns are at the Platoon Level in the Weapon's Squad, but your gun teams often are tasked to the Squads depending on the mission. You have 3 Rifle Squads (each with 2 SAW per), and a Weapon's Squad, with (2) 3-man Gun Teams.



We might initiate an offensive operation where the Gun Teams are in the support element on the support-by-fire position with good fields of fire and overwatch on an objective, while the assault element moves onto and seizes that objective during the initial stages of the attack. Once security has been established, the SBF will either collapse onto the objective, or maintain overwatch for the assault element to withdraw (raid).

There really is no way to make this GPC concept work, unless you can get match-or-exceed 7.62x54R performance from the same weight as the current 5.56 NATO space-weight profile, and that isn't going to happen. No NATO Army is looking for a one-size fits all solution here, because it simply isn't realistic. The Army Caliber Configuration study seems to be addressing the weight penalties of the larger calibers, and finding lighter weight solutions to them.

The next logical step is replacement calibers for .50 BMG, and possibly 7.62 NATO. 5.56 NATO is one of the strengths in the system, not a weakness.

[Ridgerider]

In the US Army Infantry, 7.62 NATO Medium Machine Guns are at the Platoon Level in the Weapon's Squad, but your gun teams often are tasked to the Squads depending on the mission. You have 3 Rifle Squads (each with 2 SAW per), and a Weapon's Squad, with (2) 3-man Gun Teams.



We might initiate an offensive operation where the Gun Teams are in the support element on the support-by-fire position with good fields of fire and overwatch on an objective, while the assault element moves onto and seizes that objective during the initial stages of the attack. Once security has been established, the SBF will either collapse onto the objective, or maintain overwatch for the assault element to withdraw (raid).

There really is no way to make this GPC concept work, unless you can get match-or-exceed 7.62x54R performance from the same weight as the current 5.56 NATO space-weight profile, and that isn't going to happen. No NATO Army is looking for a one-size fits all solution here, because it simply isn't realistic. The Army Caliber Configuration study seems to be addressing the weight penalties of the larger calibers, and finding lighter weight solutions to them.

The next logical step is replacement calibers for .50 BMG, and possibly 7.62 NATO. 5.56 NATO is one of the strengths in the system, not a weakness.

Dont you mean 7.62x 51 Nato as the 7.62x54 was a former Soviet now Russian Federation round