Requirements for Replacement of Currently Issued 5.56 M-855 and 7.62 M-80.

[JASmith]

Stan,

I understand your point --- and feel that much of the existing ballistics test data -- interior, exterior, and terminal -- already supports our investigation. the admiral's test won't do much absent a relevance statement. The thing we're working in this thread does that.

It also does that in a way that allows trades in capability and costs, making it very powerful during the advocacy phase. The document we are working will establish relevance in the bean-counting world and, more importantly, let us would-be developers understand what is doable given the multitude of constraints.

Heck , who knows but what we find that the existing pair of cartridges is the best that can be done given all of the constraints?!? The chances are, however, that our effort will establish a viable technical path to a capability more in tune with the needs of our soldiers. I am also sure that we'll find a surprise in what pops out as a "best fit" for the needs...

[stanc]

Stan, I understand your point --- and feel that much of the existing ballistics test data -- interior, exterior, and terminal -- already supports our investigation. the admiral's test won't do much absent a relevance statement. The thing we're working in this thread does that.

It also does that in a way that allows trades in capability and costs, making it very powerful during the advocacy phase. The document we are working will establish relevance in the bean-counting world and, more importantly, let us would-be developers understand what is doable given the multitude of constraints.

Yeah, I'm sure you're right, Joe. It's just that I've been discussing and writing about this for more than a decade, and I have reached the point where I think it is past time for talking, and now it's time to start shooting.

http://www.youtube.com/watch?v=VUslGSoEH8I

But hey, don't mind me. I'm just venting my frustration...

[JASmith]

...I've been discussing and writing about this for more than a decade, and I have reached the point where I think it is past time for talking, and now it's time to start shooting...

That's always been one of my favorite scenes.

I've tilted at windmills a time or two myself. Did you know that it takes 20-30 years on average to get a weapon system into initial operational readiness.

I've felt that frustration more than once...

[Tony Williams]

Tony:

If ammo weight is a requirement, you must state your requirements in priority.
If recoil forces are a requirement, state the requirement in terms of energy and then prioritize that requirement too.
You guys can't invent rules every time you are faced with reality. Where does ammo weight stand in terms of recoil? How about ammo weight in terms of overall cost? How about ammo weight in terms of penetration and lethality? First -- state your requirements. Second -- prioritize them.

As far as I'm concerned, the requirements list I stated in post #6 on this thread all have to be met for any new round to be successful. The requirements are stated in terms of comparisons with existing 7.62mm M80 and 5.56mm M855 in similar guns, as follows:

"compared with the M80, to reduce the weight to 80% (assuming similar materials) and to reduce the recoil energy in a similar rifle to 60%

compared with M855 ammunition, to limit the weight to 160% (assuming similar materials) and to limit the recoil energy in a similar rifle to 200%"

I will simply put ammunition weight lower on my priority as guys are used to carrying 7.62 and don't seem to be complaining about its value.

The British Army would disagree with you - they regard reducing the massive burden worn or borne by foot soldiers as a high priority.

You see, no one here can tell me -- the developer -- what you expect out of the ammunition. You guys state 'same vertex as M-80, same Ke at 1K meters' without even being able to state why 1K is required. You guys talk about 1K being some magical distance for M-80 ball. This is another example of someone blindly claiming a requirement because it sounds reasonable when in fact it is unnecessary. What small arms optic allows anyone to see and ID an enemy that far? Not the Elcan -- you may see mirage and blurs that far but you won't be able to tell if what you are seeing can be determined to be an enemy or not. An example of blindly following Cold War Europe requirements made up in the 50's and were based on myths gathered from from WWI and WWII.

Actually, not. The driver for the range requirement has been set by the recent experience of both the US and UK armies in Afghanistan, where at least half of all small arms engagements are reported to take place in the 300-900 metre range bracket - far more than would have been assumed from WW2 experience or Cold War expectations.

As Joe pointed out, the range requirement is currently mainly concerned with MGs first, DMRs second. However, the steady development of improved sights is making long-range shooting much easier for ordinary infantrymen. The 6x Elcan sight used by UK troops with the L129A1 is highly regarded, and much better things are on the way.

It is already possible to buy sights incorporating laser rangefinders and ballistic computers which will indicate the precise aiming mark required for the distance lased, taking into account weapon cant plus uphill and downhill shooting. These are mainly focused on grenade launchers at the moment, but clearly have rifle/MG applications. These will make a flat trajectory less significant than before.

The DARPA One-Shot programme aims to improve sights even further by incorporating a means of measuring wind drift and building that into the fire control solution. These are intended for snipers initially, and will of course be very bulky, heavy and expensive. But it's a very safe bet that once they are introduced into service, they will become steadily smaller, lighter and cheaper, and will find their way down; first to MGs, then to infantry rifles (just as scope sights have). With sights like these, any infantryman should be able to deliver effective fire to very long range in suitable conditions - provided that the ammo is capable of it.

Today you must positively ID the target as a threat before you shoot and you better not kill an innocent. You guys can't comprehend this or you would be stating accuracy requirements in terms of reducing risk as well as increasing lethality.

You don't seem to grasp what I comprehend, Gene. If you read my presentation on this subject here: http://www.quarry.nildram.co.uk/The%20Ne...ration.htm you will find that the first two sentences are:

"The conflict in Afghanistan, with its emphasis on targeting specific enemy individuals while avoiding collateral damage, demands the use of weapons of high precision and limited destructive effect. As a result, infantry small arms have a much more prominent role than that expected in conventional high-intensity warfare and this is highlighting the performance of their ammunition to a greater extent than ever before."

[LRRPF52]

Tony,

For the sake of this discussion, let's say we're only talking about dismounted, Light Infantry operations in terrain similar or equal to the Afghan AOR. The smallest element that a "looking-for-trouble" unit will usually operate in will be a platoon or a Squad + at the minimum. A "Squad +" usually means with a 2-3 man gun team tasked to them and an RTO with a PRC-119 ASIP SINGARS radio. A Squad + in a good unit that knows how to fight its hooahs will send them out with at least one or two DM's if DM's aren't organic to the MTOE, a combat medic, and maybe even a Forward Observer with another -119. Platoons don't usually like letting go of a Squad Leader w/ those PLT and Company-level assets, but let's say that the guys are given a loose leash and they're out conducting a Squad-sized ambush. We've pretty much set them up for a worst-case scenario as far as doctrine goes, because you would preferably like to fight with 3-to-1 odds in your favor. The 9-man squad has now been augmented with 3 guys from the weapon's squad w/240, an FO, an RTO, 2 DM's, and I'll bet the Lieutenant insisted on coming along too. The Squad is now two squads.

So they make chance contact from some well-tuned Muj who have lit them up with the most common thing they like to do in that terrain: the coordinated far ambush with PKM's and RPG's, and maybe an SVD...say from about 300-700m. The Super Squad initiates their Immediate Action Drills and seeks cover behind some boulders or the terrain available. The FO and RTO will immediately be on the -119's calling in the contact and the Fires Officer at Battalion should allocate them the most available and appropriate indirect or Close Air Support assets.

While that game is playing out, the 240 team has gotten into position along with the DM's, SAW gunners, and riflemen, who should be talking with each other at this point. If they are pinned so bad they can't get into position, they simply wait for the CAS, Artillery, or Mortars, while preparing for a possible assault on their position. If they do gain good positions, the guns will start talking, and Team Leaders will control the rate of fire of their SAWs. If any even close to effective small arms fire is raining on the Muj, they will either: 1) ignore it since they fear no death, or...2) run away to fight another day. Maybe they break contact or hold their position and burn through 7.62x54 and RPG rockets until they're tired, then move out.

If a worst-case occurs with the politically-sensitive battlespace managers sitting back in their air-conditioned hangars at Kandahar or Kabul, and all CAS or indirect assets are denied for fear of impacting the desolate ecosystem from whence the Muj have initiated, and a Muj maneuver element is brought into play to assault the Joes in their hasty position, they will have to prep for a close attack. The Patrol leader will keep a certain group oriented towards the Muj Support-by-Fire position, and another group oriented towards the attackers. The 203's will be brought into play at about 400m, and the SAWs will already be plunging controlled busts into the Muj out to 800m in a cone of fire/beaten zone, unless they go down from malfunctions (pretty common with that system).

The DM's engage targets of opportunity and priority, and probably won't start being effective until the Muj assaulters get within 600m, but will have a significantly-increased hit probability at 550m and closer, regardless of whether or not they are using L129A1's, M110's, 5.56 SPR's, or M4's with good optics and 77gr Mk262. There will be very little time to estimate range, but if the guys were doing their jobs and conducting frequent map checks on their en-route rally points and security halts, they should have a good feel to how far the key terrain features are off of their route to within about 75-100m of error.

If the series of worst-case scenarios described stacks up against this small unit, and they are facing an assault, ammunition will count a lot, as in plenty of it. Good leadership and situational awareness combined with a war-fighting spirit, followed by practical marksmanship and small unit tactics will prevail in this encounter. The mix of 5.56 and 7.62 NATO actually are quite well-suited for it. The one caliber/weapon system that would give a major edge to this equation would be the .50 BMG/M107 combo. That could and has convinced the booger-eaters that breaking contact is a better course of action for them.

If I knew in advance that this scenario were to happen to me, I might lean towards having another gun team and at least 4 hooahs with 7.62 auto-loaders like the M110, or 2 M110's and 2 5.56 SPR's, but I would not want to cut my 5.56 guys down drastically since they can carry 2-3 times what the butt fingers will have in an AK chest harness, and my guys will usually be able to carry a 100rd box of 7.62 linked for the gun teams or a 200rd drum for the SAWs when we cross-load during mission prep. Those are two common additional loads to be dumped on riflemen, in addition to other special items of squad equipment.

Now, let's throw the magic switch and say that these guys can have any caliber we want. How about a hypothetical .280 Enfield in match-grade Bullpups with modern metallurgy pushing 7mm Multi-Purpose, barrier-blind, eco-friendly, 2" neck penetration and 90 degree yaw on heated ballistic gelatin with bone simulation, engine-block crumbling projectiles with .6 G1 BC's at 2800 fps, which is way faster than the original cartridge. That cartridge would be awesome for the gun teams, especially for the SAWs and 240's, which could be one platform now, as well as for the larger DM rifles. It would give the reasonably-trained rifleman probably a 50m to maybe 75m increase in hit probability compared to 7.62, and add at least 100m of hit prob to the well-trained DM or sniper.

The rest of my hooahs should most probably NOT have that caliber in their carbines, as it would add significant weight to their loads, and thereby reduce their carrying capacity for basic load and squad equipment. Even a lighter 120gr projectile weighs about twice as much as M855, not counting brass.

The next issue would be logistics, even if we waved a magic wand and converted every minigun, crew-served weapon, and tank coax in the entire NATO inventory, because the longer projectiles with awesome BC's would have a longer bearing surface in the rifling, which would most likely lead to shorter barrel life, unless we nitro-carb'd, but that isn't full-auto rated since it is a 70 rockwell hardness. Which takes us back to square one. Given modern metallic ammunition and the limitations of the technology, we are pushing the threshold of what is practical when all things are considered. The investments we would have to make for a marginally-better caliber don't pay off when compared to what Joe can do with it, and how unnoticeable the advantages would be in actual combat, except for the as-of-yet hypothetical lighter/smaller multirole machinegun.

This is not meant as a discouragement, because there eventually will be a replacement for these calibers, and all the number-crunching will feed into the next proposed solutions, RDT&E, and what is actually fielded to our grandkids. I would like to see my Machine-Gunners get a lighter profile gun and ammo system, with less weight, and equal or better ballistics to the 7.62 NATO with 60% of the recoil or less, with the same or better barrel life for the pipes. The M4/5.56 is an excellent system and only really needs the original fire-control mechanism (AUTO-not for auto, but for the consistent trigger pull), a long free-float tube, and Mk262 for the DM's that use an AR family precision rifle with some basic tune-ups. Giving much more caliber-wise to my riflemen/assaulters will be counter-productive, in my opinion, especially when they need to make their money for the close-in fight. They definitely will not be making predictable 700-900m hits with anything other than a laser gun or the Barrett (with some training that we just can't give to every Joe), that I can promise you, regardless of the enemy situation.

I have a hard enough time making those hits with a .260 Rem pushing match bullets with .5 or higher G1 BC's at over 2850 fps in bad conditions, and that's in my comfy clothing with no real stress, and I've spent the better part of my life shooting on a regular basis, to include long-range shooting with formal training and a lot of time behind spotting scopes in military settings as the norm. Maybe a DARPA unobscopium would be able to project a thermal interpretation of chaos theory and fluid dynamics with regards to doping the wind so I could really be an idiot, but the costs of such an optic/one-station ballistics unit would be wasted on 1st-term grunts who can barely qualify Sharpshooter on a qual range with targets that go out to only 300m. Unless the $50k DARPA optic comes with soldier stabilization and a Predictive Human Error Gun Enabling Turret-Infantry Troop model (PHERGET-IT), the taxpayers will really be wondering what is happening to their money.

So that being said, I still would like to see the caliber and projectile we're talking about, but understand that it should have a limited role to the machineguns, designated marksmen rifles, and intermediate sniper rifles. Carbines and basic riflemen need to have freedom of maneuver, and be able to carry a significant load for their individual weapon, as well as the for the pigs. I just want anyone who is genuinely concerned over this to realize that this is not a caliber issue so much, and any projectile limited by modern metallic cartridge technology that reasonably fits into a soldier's load will not have much positive affect, if any, for a basic rifleman duty position.

Sorry for the rant, just my perspective and fallible opinion.

LRRPF52

[Tony Williams]

Thanks for that, Gene. Judging by the unofficial* feedback from British forces which I have seen, the views you express here are held by about half of the troops who have expressed an opinion. The other half are unhappy with 5.56mm performance and effectiveness and would like something more powerful to replace it. Some would even go so far as to readopt 7.62mm instead of 5.56mm. One interesting comment from the Royal Marines is that they found that using 7.62mm rifles tended to encourage troops to pick and choose their shots rather than throwing loads of ammo at possible targets, and the reduced ammo loads therefore tended to last longer.

(*The official British position, like the US one, is that there is absolutely nothing wrong with either 5.56mm or 7.62mm as they are now and we will go on using both of them for evermore without ever seriously considering anything else.)

[Tony Williams]

Yup. BTW, I just finished reading your "Why Bullpups?" article.

http://www.quarry.nildram.co.uk/bullpups.htm

Since it wasn't mentioned therein, you might be interested to know that the SAR-21 bullpup -- despite right-side ejection -- can be fired from the left shoulder. Some years ago, I had the chance to shoot a SAR-21, and noticed the ejection pattern was such that the empty cases appeared as though they would not hit a "lefty" in the face. Just to be certain, I fired it from the left shoulder, and had no problems with the ejection.

That's interesting, Stan. I've never examined a SAR-21, but I've heard good things about it from users, the main criticism being that the issue optical sight is useless at night since the aiming point can't be seen.

How do they get over the left-handed problem - is the port a long way forwards, or does it just eject the cases in a forwards direction?

[JASmith]

REF LRRPF52 Post #65:

LRRPF52 -- Good background discussion. Can you suggest a couple of 1 or 2 sentence descriptors of the cartridge for the new squad weapon? We don't need specifics like caliber and bullet weight, but need a description what the cartridge should be able to do. Remember that matching a current capability for a threshold is OK. But, the objective should be attainable with current mature technology. Tony has indicated that the current exercise has an eye toward defining the next generation system using the resulting cartridge(s).

Tony -- Reference cartridge weight, I missed, or forgot, whether the weight reduction included the adoption of plastic cases.

Stan -- The system LRRPF52 describes is something that sounds a lot like the Squad Automatic Weapon system of the '70s where a third caliber was introduced. Thoughts?

Cheers!
Joe

[Tony Williams]

Tony -- Reference cartridge weight, I missed, or forgot, whether the weight reduction included the adoption of plastic cases.

The weight reduction from 7.62mm in my original spec assumes brass cartridge cases. Obviously, switching to plastic LSAT would save a lot more weight whichever calibre is chosen - although this saves most in percentage terms with 5.56mm as this has relatively light bullets. 5.56mm M855 bullets weigh only 33% of the total brass-cased cartridge weight, 6.5mm probably 45% and 7.62mm around 40%.

[stanc]

That's interesting, Stan. I've never examined a SAR-21, but I've heard good things about it from users, the main criticism being that the issue optical sight is useless at night since the aiming point can't be seen.

How do they get over the left-handed problem - is the port a long way forwards, or does it just eject the cases in a forwards direction?

Unfortunately, Tony, those are specifics that didn't register on me. The only detail I recall with some clarity is that it had a prominent case deflector molded as part of the stock, and (rightly or wrongly) I attributed that with causing the lefty-friendly ejection pattern.

[stanc]

Stan -- The system LRRPF52 describes is something that sounds a lot like the Squad Automatic Weapon system of the '70s where a third caliber was introduced. Thoughts?

Joe, much as the 6mm SAW round appeals to me, I don't see that it's a similar situation. The 6x45 was only intended for use in a squad auto; 5.56 rifles and 7.62 GPMGs would have continued in use, making a 3-caliber system.

My understanding is that LRRP is partly on the same page as Tony, in that both would replace the 5.56mm SAW and 7.62mm GPMG with a single multi-purpose MG firing the new cartridge, and likewise with 5.56 and 7.62 DM rifles. But, where Tony would also replace standard infantry rifles and carbines to create a one-caliber system, LRRP would retain two calibers -- 5.56mm in addition to the proposed 6.5/6.8/7mm.

[JASmith]

Ref Post #69 --

Tony,

Thanks! I'll try to work that into the next weight requirement discussion.

Joe

[JASmith]

...My understanding is that LRRP is partly on the same page as Tony, in that both would replace the 5.56mm SAW and 7.62mm GPMG with a single multi-purpose MG firing the new cartridge, and likewise with 5.56 and 7.62 DM rifles. But, where Tony would also replace standard infantry rifles and carbines to create a one-caliber system, LRRP would retain two calibers -- 5.56mm in addition to the proposed 6.5/6.8/7mm.

Stan,

Thanks! I had missed the sublety. Am hoping the document will build will be flexible enough to allow competing these options as well as minor mods to existing ammunition types.

When we've done that, whichever one pops out as superior in all scenarios is the one we can advocate with confidence. Of course, we may not be that fortunate...

Joe

[stanc]

The rest of my hooahs should most probably NOT have that caliber in their carbines, as it would add significant weight to their loads, and thereby reduce their carrying capacity for basic load and squad equipment. Even a lighter 120gr projectile weighs about twice as much as M855, not counting brass.

True, but you can't just compare bullet weight. Tony's 6.5mm cartridge does not weigh twice as much as the complete M855 round. Here are some rough estimates I put together:

• 5.56 M855 – 7 x 30-rd mags = 210 rds @ 9.2 lbs
  6.5 GPC ––- 7 x 25-rd mags = 175 rds @ 10.5 lbs
  

The above assumes steel magazines, since I think that's what the British L85 rifle uses. It also figures on 6.5 magazines of the same length as 5.56 mags. Note that total weight for 6.5 is only 14% greater, a mere 1.3 pounds. Also, while number of 6.5mm rounds is 17% less, the number of "stowed kills" may actually be greater than for 5.56mm.

Unless the $50k DARPA optic comes with soldier stabilization and a Predictive Human Error Gun Enabling Turret-Infantry Troop model (PHERGET-IT)...

Too funny!

[warped]

Ideally I would opt for a one caliber system, although we would need to address the needs of the DM and Sniper Support roles.

I would opt for Grendel, then .260rem for longer range before jumping up to .338Lapua for sniping and .50BMG for the M2HB

I do not see a need for any other intermediary cartridges.

[Tony Williams]

Ref Post #69 --

Thanks! I'll try to work that into the next weight requirement discussion.

Just to follow up on this: in average round figures and using brass-cased ammo, 5.56mm M855 weighs 12 grams, of which 4 grams is the bullet. 7.62mm M80 weighs 24 grams, of which 9.5 grams is the bullet. An intermediate round like the Grendel weighs around 18 grams, of which 8 grams is the bullet.

The plastic-cased LSAT 5.56mm round with a 4 gram bullet weighs 8.3g (in the MG application there is a further weight saving as the plastic links weigh only 0.5 gm each instead of 2.0 gm, so the total weight of 5.56mm ammo plus one belt link is 14 gm in brass cases, 8.8 gm in LSAT). So the weight of the case and propellant drops from 8 gm in brass cased to 4.3 gm in LSAT, a reduction to only 54%.

Applying this to the 7.62mm M80 gives you a reduction in the weight of the case and propellant from 14.5 g to 7.8 gm, for a total LSAT cartridge weight of 17.3 gm.

Applying this to the Grendel provides a reduction in case+propellant from 10 gm to 5.4 gm, for a total weight of 13.4 gm.

So on the basis of the assumption that the percentage weight saving for the case+propellant elements would be the same in each instance (which may be incorrect - there may be other factors I am unaware of) the weight of LSAT equivalents of the three rounds would be: 5.56mm = 8.3 gm, 6.5mm 13.4 gm and 7.62mm 17.3 gm. Or ratios of 1:1, 1.6:1 and 2.1:1.

To put it another way, for the same weight as 100 rounds of 7.62mm LSAT you would get approximately 130 rounds of 6.5+mm and 210 rounds of 5.56mm. These are not very different from the ratios between the current brass-cased versions of the ammo.

[JASmith]

Ideally I would opt for a one caliber system...

Folks are arguing both sides of this one and many of these people are very knowledgeable about the issues. To my knowledge, no one to date has forwarded a compelling argument for either a one caliber system, the current practice, or a variant.

One of my hopes is we can help resolve the question semi-analytically. The draft requirements statement we are working to build is one step.

I believe there have been studies that address the costs of increasing the variety of items in a logistics chain. That would be one aspect of the trade between a single-cartridge/single load system.

Another is training and ammo exchange within small units.

How can we quantify? Are there any public domain trade studies that address?

[LRRPF52]

Gents,

I'm in favor of a 3-caliber (really 5+) system for shoulder-fired weapons for dismounted infantry soldiers:

Caliber 1: Riflemen should have an improved M4 carbine (including the British-just look at what SAS and SBS carry and you won't see L85A2's) with a cartridge that does not weigh more than 5.56 NATO, does not sacrifice 5.56 NATO mag height for capacity, and can push a 55gr projectile at 3,050 fps, or a 62gr at 2,950 fps like the M4. If this could be accomplished with the 6x35mm KAC PDW cartridge from a 14.5" pipe, that would increase the load-carrying capability of my riflemen. Remember, riflemen will also be tasked to carry at least a 100rd belt of 7.62 NATO or 200rd drum of SAW or equivalent weight of linked ammo for the machineguns in their squad or platoon. When it comes time to kick in doors or fight in enclosed spaces, including streets & alleys, you don't want to be slugging it out with anything that resembles the muzzle blast of an AK or 7.62 battle rifles, and you don't want anything longer than a 16" pipe.

Caliber 2: The Multi-Role Light Machinegun Cartridge, which would be common with the Semi-Auto Sniper System (SASS) cartridge. As long as it weighs less than 7.62 NATO and not too much more than linked 5.56, & delivers 100m more 1st-round hit probability, we would have something. I think a 6.5 to 7mm diameter range would be the ticket here. Maybe something like a 6.5x47 Lapua or 7x47 Lapua, but a 6.5x47 would be a throat burner without some serious developments in propellant and or barrel metallurgy. This would replace linked 5.56 NATO, linked 7.62 NATO, and also be available in a match round for the SASS to replace M118 and M852.

Caliber 3: Long-Range Interdiction cartridge in .338 LM. This would be for snipers and DM's in the anti-material role, and would negate the limited use of .300WM in some units, while offering much of what the Barrett does to conventional units. The Brits and about every other NATO country are on-board with .338 LM anyway. There are currently-available API and HE projectiles for .338 LM as well, and the rifle chassis for .338 LM is not much more than an M24 in weight, while doubling the effective range of that weapon. With some of the developments going on with .338 LM right now, it is basically transitioning from a 1600m to 2000m effective range weapon, when using the solids out of 30" barrels. An auto-loader .338 LM would make a 29lb M107 less and less desirable as well.

In summary, only one new caliber could be introduced while phasing out 7.62 NATO, and that would be the new MRLMG/SASS cartridge. It would mean that an Infantry rifle squad would now have 2 LMG's capable of area target suppression at 1000m and beyond (7.62 is book-defined out to 1800m for area suppression), with a man-size hit probability per 1st controlled burst closer to 700m. It would also have the capacity to field 2-4 SASS rifles in the same caliber with match ammo that is lighter than 7.62, and has an increased 1st-round hit probability past 600m, that also is easier to fight with in closer ranges due to less muzzle blast and recoil.

That would leave a 9-man Squad with the Sqd LDR carrying either an M4A2 or a SASS, 2 LMG gunners, 2 M4A2 w/40mm Grenade Launchers or the new XM29, 1-2 DM's with the SASS, and 2-3 Riflemen with M4A2's. It is essential that the LMG actually be lightweight, as in 10 lbs or less, with constant recoil operating principle. As we have been encountering with the M14's and M110's, there will be more rifles assigned per squad than soldiers, leaving the unit with the flexibility to configure its soldiers for the Area Of Responsibility/Mission/etc. Another advantage to this is that current SASS rifles could be re-barreled easily when they hit their barrel wear, and the Brits don't even need to send off their L129A1's since it is an LMT Monolithic Upper Receiver with the ability of the user to change barrels with a torque wrench.

Brits/UK
With the L129A1 system, when operating in an urban environment, a 16" lightweight barrel could be installed by Joe during mission prep, and he would still be good-to-go for kicking in doors with a lighter load using a thin jacket. A 100gr 6.5 projectile out of a x47 case capacity would scream, even out of the 16" pipe, and could devastate at close range. That would also be a great 300-400 bullet in the city.

Remember, there will almost always be more than 3 types of ammunition used, even if you go to a one-caliber system, since linked ammo and magazine ammo will be issued and used in their own exclusive systems anyway, and you still have several types of Grenade Launcher rounds. The introduction of the XM29 will add a new caliber to the system, and most likely ensure the retention of 5.56 NATO or something smaller if they stick with the PDW/Burst Munition Launcher combo. The 6x35 PDW would actually work better in that system since it was purpose-built for a short-barreled AR carbine, which is exactly what the OICW has. If we could get the 6x35 to shoot it's 65gr projectiles at 2900fps out of a 14.5" or 16" barrel, that would be nice, and could initiate the replacement for 5.56 NATO. It would also open the door for a 6mm SPR in the AR platform, but mag length issues would need to be balanced between the assault rifle load and the DM load. From an end-user perspective, this is what seems to make the most sense to me, and the field is actually ripening for these moves if the XM29 gets adopted.

LRRPF52

[stanc]

Wasn't the XM29 cancelled several years ago? :confused:

[RedFalconBill]

If we could get the 6x35 to shoot it's 65gr projectiles at 2900fps out of a 14.5" or 16" barrel, that would be nice, and could initiate the replacement for 5.56 NATO.

There is no way for the 6x35 (aka 6mm Whisper and 6mm-221 Fireball) can get those types of velocities. You would need the 6x45 and an 18", or longer, barrel. Since the 65gr 0.243" bullet has the same SD as a 55gr 0.224" bullet, just how much better will a 65gr 0.243" bullet @ 2,900 fps be than a 55gr 0.224" bullet @3,200fps?

I also have not chrono'ed many M-855 rounds, that when fired out of an M-4, go much faster than 2,900 fps, let alone 2,950 fps. The bulk of the ammo has averaged 2,890 fps +/- 30 fps.