Testing, testing...

[Tony Williams]

Hmm. That's just the reverse of what I got from your "bite the bullet" article and presentations.

True, but the situation continues to evolve. The widespread distribution of 7.62mm rifles and MGs down to section level (helped by the fact that the British have just joined the US in selecting the 7.62mm Minimi) has to a large degree addressed the range and (to some extent) the effectiveness issues of 5.56mm, but has created a new problem - ammo weight!

That's what I used to think, too. However, with the switch from SAAMI to the Spec II chamber, 6.8 SPC is looking much better than it did. Muzzle velocity with bullets of the same weight and type, 6.8 SPC outdoes 6.5 Grendel by 200-300 fps. Since a new carbine/rifle/LMG need not have the M16 mag well dimensions, neither does cartridge OAL have to be 2.25 inches of the 5.56 round. Let cartridge length be 2.40 inches, and 6.8 SPC can use very streamlined bullets. Combined with the higher velocity, and now 6.8 SPC might not only equal 6.5 Grendel at long range, it might even beat it.

I wouldn't argue with that: my suggested ideal cartridge in calibres between 6.5mm and 7mm is based on the 6.8 Rem case, but slightly longer, and with space for a much longer bullet. In terms of conventional ammunition technology, I think this could represent the ideal dimensions and proportions.

If we were sticking to lead+steel cored bullets I would choose 6.5mm as the ideal calibre, but with copper+steel (or even just steel) bullets as seems mandatory nowadays, getting sufficient weight within a reasonable length becomes a problem for long, VLD bullets. So I am agnostic over the exact calibre, it all depends on how the sums work out; the answer could be 6.8mm or even 7mm.

I'm skeptical of that. The only real data we have to go on is for the 120gr Norma FMJ, which has a 0.428 BC. That's far below the 0.54 BC of the 123gr Scenar. I just don't see the BC of a 120gr FMJ getting above 0.44-0.45, and 110gr is said to be the "sweet spot" for this cartridge -- what's the likely BC for an FMJ of that weight? With a BC in the 0.42-0.45 range, to match 7.62 M80 trajectory and drift, it'd be necessary to have MV in the neighborhood of 2700 fps, and that just ain't gonna happen.

Could be. We may be able to get away with being close enough to M80 performance for the difference not to be significant, rather than exactly matching it. However, if the long-range performance falls noticeably short then the new round won't be able to replace 7.62mm and the argument for it will thereby be substantially weakened IMO. That PKM is far too widely distributed in actually or potentially unfriendly hands for the troops to be expected to face it with weapons of inferior range.

[JASmith]

True, but the situation continues to evolve. The widespread distribution of 7.62mm rifles and MGs down to section level (helped by the fact that the British have just joined the US in selecting the 7.62mm Minimi) has to a large degree addressed the range and (to some extent) the effectiveness issues of 5.56mm, but has created a new problem - ammo weight!

The plastic case technology you called our attention will make a huge difference and, and one could forecast, reduce the pressure to replace the 7.62X51 machine gun in the heavy dismounted role.

...We may be able to get away with being close enough to M80 performance for the difference not to be significant, rather than exactly matching it. However, if the long-range performance falls noticeably short then the new round won't be able to replace 7.62mm and the argument for it will thereby be substantially weakened IMO...

We (especially me) keep forgetting that we live in a combined arms world. There was a recent (History, History International, or Discover Channel - I don't remember which) segment on the Barret rifle development, history and future plans. They appear to have implemented a variant of their M-107 that uses the 25 mm grenades developed, IIRC, for the now defunct OICM family of weapons.

True -- a 16-20 lb weapon and even heavier ammunition may be challenging to lug around, but the developments are there and will affect the 1 km game. These developments show possibilities. E. g., I remember seeing discussions on the web (~5 years ago) featuring an experimental UK guided 12 gauge round.

While a guided 12 gauge round, for the time being, would almost certainly be horrifically expensive, an unguided variant could be developed today and use existing under-barrel mounts for many of the weapons already in service. Further, the payload could be combined effects, shrapnel plus a shaped charge. The shaped charge would likely be able to pierce 20-30 mm of armor plate, making it capable of defeating the most effective forecast body armor. This, coupled with sights like the Barrett BORS, could give the squad-level sharpshooter some very interesting teeth.

Bottom line -- I see these other developments as factors we can't or should not ignore.

When we factor that sort of thing into the assessment and are willing to accept one ammunition type (e. g. 85-90 gr 6.5) for box magazines and another (e. g. 115 to 130 gr 6.5 mm) for belted, while still maintaining the potential for interchangeability in emergencies, then a "one caliber" dismounted infantry solution appears feasible.

[Tony Williams]

The plastic case technology you called our attention will make a huge difference and, and one could forecast, reduce the pressure to replace the 7.62X51 machine gun in the heavy dismounted role.

That depends on how the plastic-cased technology is introduced. One thing is for sure - both the guns and ammo will require entirely different manufacturing techniques than are used at present, so there's no particular advantage in retaining an existing calibre: they could and should start with a clean sheet.

The second point is that there isn't and never will be any relaxation of the pressure to reduce the weight of portable equipment and consumables (like ammo) so if the Army can get long-range performance comparable with the 7.62mm but with lighter ammo, they're likely to go for as much saving as possible. Which takes us back to a 6.5 to 7mm round.

We (especially me) keep forgetting that we live in a combined arms world. There was a recent (History, History International, or Discover Channel - I don't remember which) segment on the Barret rifle development, history and future plans. They appear to have implemented a variant of their M-107 that uses the 25 mm grenades developed, IIRC, for the now defunct OICM family of weapons.

True -- a 16-20 lb weapon and even heavier ammunition may be challenging to lug around, but the developments are there and will affect the 1 km game. These developments show possibilities. E. g., I remember seeing discussions on the web (~5 years ago) featuring an experimental UK guided 12 gauge round.

I don't doubt that we will see developments in weapon systems (my favourite idea is here: http://www.quarry.nildram.co.uk/MetalStorm.htm ) but there will always need to be rifles for precision targeting with minimal risk of collateral damage, which takes us back to the performance we want from these and therefore to the ammo...

When we factor that sort of thing into the assessment and are willing to accept one ammunition type (e. g. 85-90 gr 6.5) for box magazines and another (e. g. 115 to 130 gr 6.5 mm) for belted, while still maintaining the potential for interchangeability in emergencies, then a "one caliber" dismounted infantry solution appears feasible.

That could work in theory, but it seems to have a dubious history in practice. Both Spain and Japan introduced low-recoil versions of the 7.62mm NATO for rifle use, but these didn't seem to last. The Chinese also introduced light (assault rifle, LMG) and heavy (sniper rifle, GPMG) versions of their 5.8x42, but have begun to move towards a compromise "universal" loading instead. Maybe the complication is felt not to be worth it.

[JASmith]

Tony,

You've done very well at positing the next family of weapons and ammunition, but an immediate step to that family may be larger than can be swallowed just now. Try to think incrementally from where we are today and where we need to go.

That depends on how the plastic-cased technology is introduced. One thing is for sure - both the guns and ammo will require entirely different manufacturing techniques than are used at present, so there's no particular advantage in retaining an existing calibre: they could and should start with a clean sheet.

Our enthusiasm needs to be tempered by the knowledge that fear of the unknown will always make change an incremental process -- unless our noses really get rubbed in it. At that point it may be too late...

The second point is that there isn't and never will be any relaxation of the pressure to reduce the weight of portable equipment and consumables (like ammo) so if the Army can get long-range performance comparable with the 7.62mm but with lighter ammo, they're likely to go for as much saving as possible. Which takes us back to a 6.5 to 7mm round.

Which is why a plastic-cased 5.56 with attachable 12 ga grenade launcher (already with plastic cases) may end up being a preferred solution. This could happen in spite of the superiority of the 6-6.5 mm class of bullets and cartridges as a result of "incremental" and "minimum weight" arguments combined.

That (multiple ammunition types) could work in theory, but it seems to have a dubious history in practice. Both Spain and Japan introduced low-recoil versions of the 7.62mm NATO for rifle use, but these didn't seem to last. The Chinese also introduced light (assault rifle, LMG) and heavy (sniper rifle, GPMG) versions of their 5.8x42, but have begun to move towards a compromise "universal" loading instead. Maybe the complication is felt not to be worth it.

We already have multiple ammunition types big time in both 5.56 and 7.62. The only remaining step is to allow the bullet weight in belted ammunition to be different than for box magazines. Indeed, there is no reason for a 100 round box magazine to have the same bullet weight as the 30 round assault rifle magazine.

Cheers!
Joe

[stanc]

...the situation continues to evolve. The widespread distribution of 7.62mm rifles and MGs down to section level (helped by the fact that the British have just joined the US in selecting the 7.62mm Minimi) has to a large degree addressed the range and (to some extent) the effectiveness issues of 5.56mm, but has created a new problem - ammo weight!

I see. Back to the future. Seems we've (partially) returned to the 1950s in that regard. Kinda funny, actually.

I wouldn't argue with that: my suggested ideal cartridge in calibres between 6.5mm and 7mm is based on the 6.8 Rem case, but slightly longer, and with space for a much longer bullet. In terms of conventional ammunition technology, I think this could represent the ideal dimensions and proportions.

It might. One advantage to the 43mm SPC case is that it can be loaded to OAL of 2.25" for conversion of 5.56x45 weapons, or to OAL of 2.40-2.50" for use in a new platform.

If we were sticking to lead+steel cored bullets I would choose 6.5mm as the ideal calibre, but with copper+steel (or even just steel) bullets as seems mandatory nowadays, getting sufficient weight within a reasonable length becomes a problem for long, VLD bullets.

I agree. Almost everybody is still looking at lead-core bullets, when they should be doing "green" projectiles. I've been guilty of this myself, even after pointing out a year or two ago that bullets for alternative calibers should be (in the USA, anyway) of the M855A1/M80A1 type.

Bill Alexander was apparently paying attention, though, as he's trying to get a T3 bullet made for 6.5 Grendel. I can't help wondering how heavy a 6.5 T3 can be, without becoming too long. My calculations (which may be faulty) say that scaling down the 130gr M80A1 would be a mere 82gr in 6.5mm, and 149gr M80A1-A, only 94gr. That would certainly boost muzzle velocity, but downrange velocity would suffer significantly.

Then there is the question of terminal effects with the necessarily long, eco-friendly projectiles. Will they be capable of early yaw in flesh? Photos of M855A1 into bare gel, which would shed some light on that question, have yet to surface.

We may be able to get away with being close enough to M80 performance for the difference not to be significant, rather than exactly matching it. However, if the long-range performance falls noticeably short then the new round won't be able to replace 7.62mm and the argument for it will thereby be substantially weakened IMO.

Concur.

[stanc]

...a plastic-cased 5.56 with attachable 12 ga grenade launcher (already with plastic cases) may end up being a preferred solution. This could happen in spite of the superiority of the 6-6.5 mm class of bullets and cartridges as a result of "incremental" and "minimum weight" arguments combined.

Didn't Tony post a few weeks ago that the LSAT people had been directed to stop work on 5.56 CL/CT ammo?

As for the 12ga idea, have you ever tried to hit a man-size target at 200-400 yards with a conventional slug? It's difficult enough with a regular shotgun, but likely near impossible with that underbarrel thing they have now.

We already have multiple ammunition types big time in both 5.56 and 7.62. The only remaining step is to allow the bullet weight in belted ammunition to be different than for box magazines.

Joe, the military has always had multiple ammunition types, at least as far back as the .45-70 era. And they've always had a single load standardized for rifle and machine gun. Special purpose rounds have sometimes been employed (for instance, 5.56 Mk262 and Mk318) for rifles, and standard Ball ammo in machine guns, but that's an exception for mission specific requirements.

The Army's SOP was and is one bullet weight for both mag-fed and belt-fed weapons, so any proposal for two different weight Ball projectiles is pretty much a non-starter, doomed to fail.

[JASmith]

Didn't Tony post a few weeks ago that the LSAT people had been directed to stop work on 5.56 CL/CT ammo?

The plastic-cased 5.56 would not be an LSAT, but one compatible with existing weapons.

As for the 12ga idea, have you ever tried to hit a man-size target at 200-400 yards with a conventional slug? It's difficult enough with a regular shotgun, but likely near impossible with that underbarrel thing they have now.

Absolutely correct. Slugs from rifled shotgun barrels, however, can get closer to 1 moa.

Further, we're talking about a bursting round with an effects radius of at least 2-3 meters -- the effective target then becomes a tad larger than the standard silhouette.

The Army's SOP was and is one bullet weight for both mag-fed and belt-fed weapons, so any proposal for two different weight Ball projectiles is pretty much a non-starter, doomed to fail.

We currently have two different weights in 5.56 used in both rifles and machine guns. The 7.62 AP type is a heavier bullet than the M80 round.

The single bullet weight is generally driven by a desire to map trajectories into each other. That would not apply when differentiating by weapon type.

Regardless of what one calls it, bursting rounds reaching out to a km are almost certainly near-term implementable. That will change the requirement and drive the infantry round to a smaller caliber than 7mm and possibly mandate retention of the 5.56.

We need to see what cartridge would fare well in that environment. The same holds true for Tony's vision of replacing both with a single cartridge -- which seems to suggest a 6.5 - 7 mm cartridge somewhat longer than the 5.56.

Bottom line -- The more forcefully we argue for a particular solution at this point, the more we appear to have intuited the best choice and are building our analyses and testing to "prove" the correctness of our intuition. We are all more or less guilty of that tendency, so have to be especially careful to start with broad assumptions and see where the sticks fall.

[stanc]

The plastic-cased 5.56 would not be an LSAT, but one compatible with existing weapons.

Been tried, many times. Hasn't worked.

We currently have two different weights in 5.56 used in both rifles and machine guns.

But not two different weight Ball rounds. Even the USMC, which is currently using two different type bullets for rifle and LMG (in Afghanistan), still uses the same (62gr) weight bullet in both weapons.

The 7.62 AP type is a heavier bullet than the M80 round.

Actually, the current 7.62 AP has a lighter bullet than the M80. And AP is not the standard load. It's a special purpose round, with limited use.

The single bullet weight is generally driven by a desire to map trajectories into each other.

I don't know what you mean by that. AFAIK, using a single bullet weight (and type) is primarily an application of the KISS principle.

The more forcefully we argue for a particular solution at this point, the more we appear to have intuited the best choice and are building our analyses and testing to "prove" the correctness of our intuition.

"What do you mean, 'we', white man," Tonto said to the Lone Ranger, as hostile Indians were closing in.

[stanc]

Slugs from rifled shotgun barrels, however, can get closer to 1 moa.

Further, we're talking about a bursting round with an effects radius of at least 2-3 meters -- the effective target then becomes a tad larger than the standard silhouette.

And yet the 20mm warhead for the XM29 OICW has considerably more explosive compound and fragmentation ability than the tiny 12ga HE projectile, but was deemed inadequate in casualty radius and superseded by a 25mm round.

[JASmith]

Stan, Tony, et. al.,

We need to understand the arguments and technologies, e. g., plastic-cased 5.56 and bursting 12 gauge shells not from the likelihood they will be introduced, but from the point of view of arguments to against implementing something new.

Someone clinging to the notion that the 5.56 and the 7.62 are perfectly fine and "the best we can do" will gleefully grab these and even very speculative emerging technologies to "prove" that we need do nothing.

This makes the chore of advocating a new cartridge, or anything else new, enormously more difficult. So, whether one or more of us is convinced something will or won't happen, we need to carry options to deal with those alternatives.

For example, Tony argues that the imminent to near-term implementation of plastic-cased ammunition in 5.56 and 7.62 can be a trigger point opening the door for a unified cartridge. Not all of us draw the same conclusion. Nonetheless we spend a lot of time debating the configuration and merits of that cartridge.

Similar attention needs to be given to equally plausible alternative paths. To repeat my previous post, we need to consider the alternatives and dispense with them, even our favorite ones, on arguments more convincing that "that has been tried before." Technology changes with time, and that change opens the path to implementing long-standing ideas previously discarded because the then-new technology, threat, or fiscal environment couldn't support implementation.

[stanc]

...whether one or more of us is convinced something will or won't happen, we need to carry options to deal with those alternatives.

Joe, it seems to me that you're overthinking this matter and making it immensely more complicated than it needs to be.

The goal is a simple one: Develop a cartridge that's significantly better than 5.56x45, without incurring excessive penalties in weight and magazine capacity.

For those who think a smaller, lighter round than 7.62x51 is needed for GPMG use, the goal is a cartridge with performance "good enough" to replace 7.62x51.

...attention needs to be given to equally plausible alternative paths. To repeat my previous post, we need to consider the alternatives and dispense with them, even our favorite ones, on arguments more convincing that "that has been tried before." Technology changes with time, and that change opens the path to implementing long-standing ideas previously discarded because the then-new technology, threat, or fiscal environment couldn't support implementation.

Give attention to plausible and feasible alternatives, certainly. But, I see no logic in being concerned with ideas that have been shown to be implausible or otherwise not worth pursuing. The task is difficult enough without devoting time and $$$ on ideas that have been demonstrated to not be viable.

[stanc]

LR1955 and others have argued that probability of hit out to 400-600 meters is of critical importance and that any new system needs to shine in at least one area.

Given the fundamental need to get a hit, it seems odd that we've spent a lot of time discussing on-target effects, ammunition weight, and recoil but almost none on trajectory and wind-drift. These areas are ones where higher-velocity and moderately well-shaped bullets might result in a significant improvement.

If we were sticking to lead+steel cored bullets I would choose 6.5mm as the ideal calibre, but with copper+steel (or even just steel) bullets as seems mandatory nowadays, getting sufficient weight within a reasonable length becomes a problem for long, VLD bullets. So I am agnostic over the exact calibre, it all depends on how the sums work out; the answer could be 6.8mm or even 7mm.

We may be able to get away with being close enough to M80 performance for the difference not to be significant, rather than exactly matching it. However, if the long-range performance falls noticeably short then the new round won't be able to replace 7.62mm and the argument for it will thereby be substantially weakened IMO.

Curiosity got the better of me, so I ran some tables for comparison. Had to make some assumptions, estimations and extrapolations regarding muzzle velocities from 20-inch barrels, but I think the figures are fairly close. On the .277" and .264" bullets, I used the BCs for Barnes' solids as the best available surrogates for eco-friendly, military ball projectiles.

Range - yards _0_ _100 _200 _300 _400 _500 _600 _700 _800 _900 1000

.308" 147gr @ 2700fps BC=0.418
Velocity - fps 2700 2488 2285 2094 1912 1740 1579 1435 1306 1198 1111
Energy - ft-lb 2379 2019 1705 1430 1193 _988 _814 _672 _556 _468 _403
Path - inches 0.0 44.6 83.7 116.0 140.4 155.2 158.5 147.8 120.3 72.2 0.0
Drift - inches 0.0 _0.4 _1.6 __3.7 __6.9 _11.3 _17.0 _24.2 _33.1 43.6 55.9

.277" 120gr @ 2600fps BC=0.438
Velocity - fps 2600 2402 2213 2033 1862 1700 1550 1415 1294 1192 1110
Energy - ft-lb 1801 1537 1304 1101 _924 _770 _640 _533 _446 _379 _328
Path - inches 0.0 46.7 87.4 121.0 146.1 161.1 164.2 152.7 123.8 74.1 0.0
Drift - inches 0.0 _0.4 _1.6 __3.7 __6.9 _11.2 _16.9 _24.1 _32.8 43.1 55.0

.264" 110gr @ 2600fps BC=0.452
Velocity - fps 2600 2408 2224 2049 1883 1725 1577 1443 1322 1219 1134
Energy - ft-lb 1651 1416 1208 1025 _866 _726 _607 _509 _427 _363 _314
Path - inches 0.0 45.5 85.1 117.6 141.8 156.2 158.8 147.5 119.4 71.4 0.0
Drift - inches 0.0 _0.4 _1.5 __3.6 __6.7 _10.8 _16.3 _23.1 _31.4 41.4 52.8

Verry intrresting, no?

Arggh! The new forum format is too narrow for 1000-yard data. I guess future tables will have to be limited to 800 yards...

[JASmith]

...Give attention to plausible and feasible alternatives, certainly. But, I see no logic in being concerned with ideas that have been shown to be implausible or otherwise not worth pursuing. The task is difficult enough without devoting time and $$$ on ideas that have been demonstrated to not be viable.

I've been there with other but still relevant military systems. The point is that the alternative cartridge will not be in competition with either 5.56 or the 7.62 or both. It will compete with other candidates whose adherents also believe their concepts are superior.

That's the major reason why I suggest a look at these alternatives. Our concept will need to both be significantly better in at least one aspect than the existing ammunition types and somehow be more attractive than these alternatives.

Some of the new-old ideas will prove to be viable and will affect the application space.

To repeat one more time -- the detractors will grab any specious argument.

[JASmith]

Thanks for doing the legwork on the table!

I know you didn't, but it sure looks like the muzzle velocities and bullet weights were chosen to make trajectories for the three calibers look the same...

We don't seem to be getting traction on the long range game with these choices. That's the reason I have advocated looking at lighter, smaller bullets for the assault rifle and thinking about a half-kilometer instead of a full kilometer.

[stanc]

The point is that the alternative cartridge will not be in competition with either 5.56 or the 7.62 or both. It will compete with other candidates whose adherents also believe their concepts are superior.

Well, sure...it would compete with other intermediate cartridges, such as Cris Murray's 7mm UIAC. But I don't understand how plastic-cased 5.56 or 12ga mini-grenades have any relevance. :confused:

[stanc]

Thanks for doing the legwork on the table!

I know you didn't, but it sure looks like the muzzle velocities and bullet weights were chosen to make trajectories for the three calibers look the same...

It does sorta look that way, but no, I didn't. Weight of 7.62 M80 is what it is. I used 110gr for 6.5 and 120gr for .277, because they are the only solid spitzers that Barnes offers.

Oh, crap. I just realized that I used MV for a 110gr .277 load, with a 120gr bullet. :o

Will rerun the .277 table, using an estimated MV of 2600 fps.

We don't seem to be getting traction on the long range game with these choices. That's the reason I have advocated looking at lighter, smaller bullets for the assault rifle and thinking about a half-kilometer instead of a full kilometer.

Considering the seemingly low probability of replacing 7.62x51, together with (as Gene has pointed out) the combined effects of short barrels, low-magnification optics, and the less-than-match grade accuracy of service ball ammo, I'm inclined to agree.

[stanc]

Oh, crap. I just realized that I used MV for a 110gr .277 load, with a 120gr bullet. :o

Will rerun the .277 table, using an estimated MV of 2600 fps.

Okay, that's done. Made for very little change, except in retained energy. Still is negligible difference between them in trajectory and wind drift.

[Tony Williams]

Tony,

You've done very well at positing the next family of weapons and ammunition, but an immediate step to that family may be larger than can be swallowed just now. Try to think incrementally from where we are today and where we need to go.

I am, which is why I keep plugging the idea of firming up on the required calibre and ballistics using conventional technology first (preferably fielding some weapons in the new calibre for thorough testing), then transferring the lessons learned to the next phase of LSAT development.

What I am worried about is that if LSAT is adopted in 5.56mm, we'll be stuck with that calibre for ever.

If LSAT fails, then we can look at introducing the new calibre in conventional form but probably using lighter case materials (part-polymer, stainless steel and light-alloy are all being worked on at the present time).

[Tony Williams]

Then there is the question of terminal effects with the necessarily long, eco-friendly projectiles. Will they be capable of early yaw in flesh? Photos of M855A1 into bare gel, which would shed some light on that question, have yet to surface.

There's a theory doing the rounds of ammo development people in the UK that a long, pointed bullet will yaw more rapidly and reliably on impact than a short stubby one, because the if the bullet strikes with even a very small degree of yaw already (as most do), all of that mass much further back will make it a lot more unstable. I don't know if they've done any practical testing to demonstrate, that, though, and I'm rather dubious - I think that the construction and internal weight distribution has a greater effect than the shape. Just look at the difference between the yaw performance of the steel-cored 7.62x39 bullet compared with the Yugo lead-cored.

[Tony Williams]

Curiosity got the better of me, so I ran some tables for comparison. Had to make some assumptions, estimations and extrapolations regarding muzzle velocities from 20-inch barrels, but I think the figures are fairly close. On the .277" and .264" bullets, I used the BCs for Barnes' solids as the best available surrogates for eco-friendly, military ball projectiles....

Thanks for doing that, very interesting. That seems to give us more leeway to play with different bullet weights than I had thought.