Grendel as a Universal Infantry Cartridge

[JASmith]

Gosh, it's good to see this forum again!

Might as well start with an old Grendel topic -- how well it might serve as a universal cartridge for one or more nation's services.

I'd like to call your attention to these articles:

1. The "6.5 mm and the Politics of Procurement" at http://forums.delphiforums.com/autogun/m...msg=4491.1
   
2. "Grendelmania" -- series of notes at http://shootersnotes.com/grendelmania/
   
3. The "Battle Rifle Series" at http://shootersnotes.com/battle-rifle-cartridge/
   

The "6.5 mm and the Politics of Procurement" explores a replacement of both the 5.56 and 7.62 NATO rounds on a likely new platform sometime in the next 5-10 years. The discussion narrows down to a cartridge that looks like a stretched 6.8 SPC. (Be forewarned -- there were 215 posts as of the writing of this note, but the rate is slowing - likely from exhaustion!)

The Grendelmania series uses the military potential as background to focus on Grendel as a medium to large game hunting cartridge.

The "Battle-Rifle" series explores alternatives with a promising candidate that may be viewed as part of the Grendel family.

The principal difference between the Military Guns and Ammunition debate and the ShooterNotes Battle-Rifle discussion is in the assumed long range lethality requirement. One specifies that the resulting cartridge be at least as lethal as the 7.62 mm M80 round at 1100 meters. The other requires that the lethality at 600 meters be at least equivalent to the muzzle performance of 5.56 M855. Similarly, one is aggressive with assumed ballistic coefficients and the other is conservative.

I am of the opinion that the Grendel community can illuminate this debate. Let's look at these questions:

1. Is there really a need for a new military cartridge? Opinions vary widely -- and an informed discussion of what is 'good enough' may be highly useful.
   
2. Assuming the need exists, what platforms (AR15, AK, AR10, etc.) should the new cartridge be compatible with? The choices make a major difference in cartridge design flexibility, weight, and performance potential
   
3. What should be the round be capable of and at what range? Remember, this is being viewed as a cartridge capable of fulfilling the medium machine gun role!
   
4. What are the viable technical alternatives -- caseless ammunition, etc.?
   
5. etc.
   

The list can be a lot longer, and part of our discussion may illuminate the things that really count!

[RedFalconBill]

HITS is nothing more than:

(Bullet Sectional Density x Bullet Weight (in grains) x Impact Velocity)/100

How does this measure lethality?

[JASmith]

Actually, the HITS score is more precisely described as a measure of lethality potential for bullets of similar construction but different sizes. The product of velocity and sectional density gives a measure of penetration depth. The product of this and the bullet weight is a measure of or material available for fragments.

The metric allows comparisons between calibers and appears to give results reported be be consistent with a fair bit of experience.

Keep in mind that a poor impact location trumps the most lethal bullet and that the events are random, so precise measurements are problematic.

[RedFalconBill]

Actually, no it is not a precise measure of lethality. The key word in your third sentence is "appears". Bullet construction is equally important, if not more so. It is much like the OGW equation in Lyman's Reloading Manual in that it claims to be something it is not.

Read the BTB work done years ago by request of the USMC, which resulted in the Mk317 (7.62x51) and Mk318 (5.56x45).

If Big Army real wanted to increase the lethality of its current crop of carbines and rifles, they would adopt a better bullet than the M-855/SS-109, but all Big Army wants is the phased plasma rifle in the 40 watt range.

Just how would you get more 'power' (using the HITS formula) than the 7.62x51 at 100 Meters and keep the carbine under 3kg (empty, with no accouterments) and have enough firepower within the 10kg load limit that Big Army wants and not overpower the Soldiers?

[JASmith]

Ref Post #4: "Actually, no it is not a precise measure of lethality." -- That is precisely correct in the sense that impact location makes a huge difference in how the target responds. Further, the metric assumes bullets of similar construction.

As far as the "100 meters" -- my apologies, the reference is for 1100 meters (the post has been corrected). At this range, the M80 has slowed to about 1000 ft/sec. A 123 gr 6.5 projectile matches the HITS score at about 1055 ft/sec. Getting this velocity at 1100 meters with a BC of about .520 requires a muzzle velocity of approx 2550 ft/sec. This is a fairly tolerable load.

[RedFalconBill]

Considering that at ranges beyond 300m and especially past 400m the infantry squad is better off using the M-240, the added power many of the rounds touted as replacements will be wasted.

The two rounds that would be the easiest to upgrade from the 5.56x45 would be the 6x45 and the wildcat .25 Bailey. While both would be a quick upgrade, the upgrade they provide is not worth the cost.

FWIW, I think that the parameters laid down for the 6.8 SPC are about right.

1) At 100m, the SPC round, when fired out of a 16" barrel carbine, had to have at least 200fps more velocity than the 7.62x39, when fired out of an AK/AKM/AK-103.

2) When fired out of a Mk12 style carbine, the SPC round had to have more KE from 0m to 500m than the Mk262 round, when fired out of a Mk12.

Not very aerodynamic though.

[JASmith]

Can you tell me more about the .25 Bailey?

Also, the quest is for a cartridge that would fulfill the GPMG role, so it would be in either the M-240 or whatever weapon replaces the M-240.

So, the resulting cartridge would replace both the 5.56 and the 7.62 NATO rounds in just about everything but the aviation applications. I will note, however, that the folks pushing this haven't discussed the vehicular, aviation, or Gatling gun roles the 7.62 NATO is also used for. I think the discussion will ultimately have to enter this area as well, and might drive a conclusion that what we currently have is about as good as it gets.

If the debate did not include the GPMG mission but covered only the assault rifle through battle rifle, including designated marksman role, then I think a strong argument exists for a 90 gr .224" bullet in a cartridge based on the .22 PPC. Problem is that the GPMG is normally part of the platoon, and the goal is to keep the platoon lethality at least as high as it is now while either reducing weight carried or increasing number of rounds within the current weight carried. That seems to be driving the discussion to calibers larger than .224" or 5.56mm.

So, it comes down to how we define equivalence...

[LR1955]

Joe:

Here is a problem with the conditions. You are using data based off of a 123 Lapua Scenar match grade bullet in comparison with M-80. Two different animals with huge differences in quality and particularly cost. This is the major flaw in the Grendel argument. I think Lapua quotes a G-1 BC (yes, I know it isn't the right BC to use but it suffices) of somewhere around .54 I think. And that is real questionable. Certainly, such a bullet shot at 2650 will match M-80. Reduce it to a rational ball round and then things change real fast.

I believe a ball round of 6.5 G that can give any sort of reasonable velocity given current powder technology will probably be in the 110 grain range and its BC will be the same as M-80 most likely. It may be higher but I bet it won't be high enough to show statistical significance. And I doubt you will get that 110 grain bullet to leave a barrel as fast as a round of M-80 given the same barrel length. Even if it does, the HITS formula changes due to the lighter bullet.

So, the debate in terms of effective range needs to reflect the reality of a Grendel "ball" cartridge fired at what ever velocity one can get from the specific barrel length with the constant being about 30 grains of powder.

So far, I tend to agree with RFB and my view has always been that the Army can design a bullet for the 5.56 that is more lethal on humans if the Army wants to. And it is doing so and the bullet will probably give a higher degree of lethality than the issued 855. I bet the old 193 has a higher lethality potential than the 855.

A question though. Why the 1100 meter lethality range? I mean, what is the rationale for that distance?

LR55

[RedFalconBill]

Can you tell me more about the .25 Bailey?

The .25 Bailey is the .223 Remington with the shoulder pushed back 5mm, necked up to accept 0.257" bullets and the case 1.575" long.

This is done for a few reasons.

1) To keep existing case taper
2) To allow for current M27 disintegrating links
3) To have the 0.257" bullet diameter at the same point as the 0.253" 5.56x45 case neck in order to use existing 20 and 30 round magazines w/o the stacking issues other rounds have

With a 16" barrel, the Bailey sends the 100gr Sierra GK bullet out at 2,520-2,560 fps. With the 100gr Sierra MK, about 30-50 fps slower.

Also, the quest is for a cartridge that would fulfill the GPMG role, so it would be in either the M-240 or whatever weapon replaces the M-240.

I would include a third GPMG in the infantry platoon and look to getting either the M-240L or MK-48 in their hands.

If the debate did not include the GPMG mission but covered only the assault rifle through battle rifle, including designated marksman role, then I think a strong argument exists for a 90 gr .224" bullet in a cartridge based on the .22 PPC.

A 90gr match bullet is very long, would require a fast twist and is, IMO, the wrong direction to go for a general purpose Infantry firearm.

[JASmith]

The .25 Bailey is the .223 Remington...

Thanks -- that's an interesting cartridge and might be fun to shoot!

I would include a third GPMG in the infantry platoon and look to getting either the M-240L or MK-48 in their hands.

One of the possible outcomes of the discussions is very much along the lines you suggest: Get the best practicable lethality and range from the 5.56 and increase the numbers of 7.62X51. Problem with the second part is the Tony Williams debate indicates that all those M80 rounds weigh a lot.

A 90gr match bullet is very long, would require a fast twist and is, IMO, the wrong direction to go for a general purpose Infantry firearm.

You may be right, but we need to establish rational alternatives to inform a debate. The analysis suggests that the heavy bullet might work, but not necessarily as a GPMG cartridge substitute.

[JASmith]

...You are using data based off of a 123 Lapua Scenar match grade bullet in comparison with M-80. Two different animals with huge differences in quality and particularly cost...Reduce it to a rational ball round and then things change real fast.

LR55,

We've had this discussion before -- and, except for the M855 experience, I do not have data to suggest a more optimistic ballistic coefficient than you suggest. So, incorporating the "more mundane" ballistic coefficients is why the "Battle Rifle Cartridge" study listed above suggests that the Grendel is a little shy of being good enough by the standards of that discussion. The "6.5 mm and the Politics of Procurement" discussion uses the Scenar and and is looking at a full-length cartridge, so the service that adopts it would need to do a more-or-less complete replacement of infantry firearms. These folks are somewhat more optimistic with their views on realizable ballistic coefficients and their consensus is that a BC of about .52 might be attainable in a production 8 gram (123 grain) bullet. BTW, it looks like one would need 40-44 grains water capacity to get the desired 800 meter/second muzzle velocity in a 20" barrel.

So far, I tend to agree with RFB and my view has always been that the Army can design a bullet for the 5.56 that is more lethal on humans if the Army wants to.

The M855-A1 claims to do that. I am curious about how well this round fulfills the promise and what its ballistic coefficient is.

A question though. Why the 1100 meter lethality range? I mean, what is the rationale for that distance?

Ah.. this is one of the challenges of referring to three different studies to inform a debate. They each have different objectives and constraints. The 1100 meter requirement is from the discussion in Tony William's "6.5 and the Politics of Procurement" discussion. Here the desire is to replace both cartridges with a single ammunition type for the roles up to and including the GPMG. Further, the thought is that the cartridge must be demonstrably equivalent to the M80 in terms of penetration and lethality at 1100 meters.

--Joe

[LR1955]

These folks are somewhat more optimistic with their views on realizable ballistic coefficients and their consensus is that a BC of about .52 might be attainable in a production 8 gram (123 grain) bullet....Ah.. this is one of the challenges of referring to three different studies to inform a debate. They each have different objectives and constraints. The 1100 meter requirement is from the discussion in Tony William's "6.5 and the Politics of Procurement" discussion. Here the desire is to replace both cartridges with a single ammunition type for the roles up to and including the GPMG. Further, the thought is that the cartridge must be demonstrably equivalent to the M80 in terms of penetration and lethality at 1100 meters. --Joe

Joe:

I would like to see someone design a lead core and full metal jacket 6.5 bullet with a .5 BC and who can mass produce it while maintaining quality standards. Most likely some sort of hybrid between a secant and tangent ogive whose QC must be about ten times better than the current production line to maintain quality and actually show a significant improvement. I am sure it can be done but I bet that the costs would be astronomical to maintain quality standards.

I think you about max out the velocity capability of the cartridge given commercial powders with a 110 - 115 grain bullet. When you start going over 120 grains, you start to lose pretty good chunks of speed for every five grains of bullet weight. May not matter for competitive shooters but I tend towards favoring velocity over bullet weight for ball ammo use. That opens up another debate.

I understand the requirement is set at 1100 for GP machineguns. I am questioning the rationale for that distance. Guys can't see that far, can't estimate the range well enough to be effective, can't even see tracer well enough at those distances to determine if they are even close unless they use very big and very heavy thermals with spotters, any hit would be random chance and lethality would be more viewed an Act of God than even random chance.

So, perhaps in favor of the Grendel, I am questioning the distance because it is irrational in practical terms.

LR1955

[JASmith]

I would like to see someone design a lead core and full metal jacket 6.5 bullet with a .5 BC and who can mass produce it while maintaining quality standards.

That's why I'm very curious about how the M855 A-1 is performing. The web references indicate it has a steel insert for both a penetrator and a rather sharp nose. It's drag characteristics are claimed to be at least as good as the M855, which is a lot better than the shape factor suggested by the M80.

....favoring velocity over bullet weight for ball ammo use. That opens up another debate...

I can see good reasons why 2750 t0 2850 ft/sec at the muzzle are considered OK velocities for bullets with the M80 and M855 class of drag characteristics. Among other things the 300 meter drop increases rapidly at lower velocities and the payoff for increasing velocity gets progressively worse above this.

...I understand the requirement is set at 1100 for GP machineguns. I am questioning the rationale for that distance... ...Guys can't see that far, can't estimate the range well enough to be effective, can't even see tracer well enough at those distances to determine if they are even close...

I think you're right, we should have debates on both the preferred muzzle velocity for military-class bullets and on what constitutes effective shooting in an environment where the targets are generally concealed difficult to see.

While important to the current thread, discussing them in detail here may make tracking the key points challenging. The "6.5 and Politics of Procurement" is an example of a thread with a lot of good info, but the digressions made it so long that it is truly difficult to pull out the gems.

Cheers!
Joe

[warped]

M855A1 is a dog, it was poorly made and eats bbls.(powder,loose tips etc.)
It really does not help much.

There are other off the shelf bullets that would be far better.

[JASmith]

Warped,

Thanks! That's good information.

Do I gather that the accuracy isn't as good as the earlier M855?

One would think that the Army development folks would have done better after having tested "a million rounds" of the stuff!

Regarding "off the shelf" items: Seems like there are some conflicting requirements. Many of the European countries seem to be strict adherents to the agreement that one does not use deforming bullets but are OK with lead cores. The US, on the other hand, is OK with bullets that "just happen" to come apart in certain circumstances, but is damn near scared to death of lead -- a substance that humans have used and been exposed to for millenia!

[longdayjake]

I don't understand this fear of lead. It's not like there are enough bullets going into the water supply of the quantity needed to cause any kind of harm. The only lead poisoning that we should be afraid of is high-speed lead poisoning. The kind that leaves a massive hole as it exits.

[JASmith]

longdayjake,

At the risk of heading off on a tangent -- you are probably closer to the mark than not. Lead in paint, eaten by young children in has indeed been shown to cause health issues. This led to a fair bit of negative publicity and the anti-gun community saw an opportunity to make things more difficult for the shooting public...

So, yes, they are afraid of high-speed lead poisoning...

Back to the center of the thread: Regardless of the accuracy of condemnation, the reality we face is that US military small arms bullet design is rapidly moving away from lead. My view is that we need to accommodate that reality.

By keeping the discussion separate from how a bullet generates lethality (i. e., expansion, break-up, or tumbling) we can better concentrate on how to get the bullet to the target with enough mass, energy and momentum to have the potential to cause the requisite damage or injury. This accommodates the notion that at least one of the major users of small arms is moving towards bullets with a specific gravity of 7.8 to 8.0 and another takes pains to keep bullets from expanding or breaking up.

[warped]

Warped,

Thanks! That's good information.

Do I gather that the accuracy isn't as good as the earlier M855?

One would think that the Army development folks would have done better after having tested "a million rounds" of the stuff!

Regarding "off the shelf" items: Seems like there are some conflicting requirements. Many of the European countries seem to be strict adherents to the agreement that one does not use deforming bullets but are OK with lead cores. The US, on the other hand, is OK with bullets that "just happen" to come apart in certain circumstances, but is damn near scared to death of lead -- a substance that humans have used and been exposed to for millenia!

As always the best solution will always have a negative in there somewhere.

If it is for barrier penetration, it may not incapacitate, if it is for terminal effect, it may not penetrate blind barriers.

The other problem is will it even be accurate enough to be used past 400m, let alone 600m?

[RedFalconBill]

Joe,

The M855A1 bullet is designed to be a LF version of the original bullet. It is not designed to be an enhanced bullet, other than being lead free. Because of this, it will suffer from all of the issues that the M855 bullet does, plus the added cost stemming from increased production costs.

Also, they have had to get pressure waivers because it is a single source special power and a single source primer. Great, added cost with no increased effectiveness. It is not as accurate as std. M855, but still within spec...barely.

Big Army is still thinking that we are going to be fighting in the Fulda Gap and having to shoot hordes of Ivan Ivanovic's who wear soft body armor and have to shoot at steel helmets at 1/2 mile.

Using Ballistic Gel at 50m, M-855 ammo, when fired from M-4's, has a neck length of 6"+. Not very impressive, which only gives people more ammunition to dislike the 5.56 round, when it is the bullet more than anything else.

I too do not think that you can maintain QC on what is essentially match bullets by the tens of millions, at least not at a price that the DoD is willing to pay.

20" Barrels are going to go the way of $0.10 Beer and $0.25 Gas. 12.5" to 16" barrels are going to be the norm. Here, you would see a 100-110 grain bullet with an initial MV of 2,450 to 2,600 fps.

Personally, I think that the 5.56 is TOO much of a compromise, but we have been using it for over 45 years and the people I shot with it, stayed shot.

The somewhat extended ranges that we are seeing in Afghanistan only highlight what has been known since the First World War. At ranges 400m +, individual soldiers shooting at point targets is useless, essentially. This is the purview of the Designated Marksman or Machine Gunner. Soldiers do not estimate range very well, nor do they take wind into account, so without training it would not matter if they had a round that was more effective, because they would still miss.

[JASmith]

20" Barrels are going to go the way of $0.10 Beer and $0.25 Gas. 12.5" to 16" barrels are going to be the norm. Here, you would see a 100-110 grain bullet with an initial MV of 2,450 to 2,600 fps.

Are you suggesting that 2450-2600 ft/sec is a desirable MV, or are you indicating that that's all we might get from a particular cartridge?

Personally, I think that the 5.56 is TOO much of a compromise, but we have been using it for over 45 years and the people I shot with it, stayed shot.

What do you have in mind for cartridge more suited to our needs?

...Soldiers do not estimate range very well, nor do they take wind into account, so without training it would not matter if they had a round that was more effective, because they would still miss.

Does this mean that the solution is better and more training and stay with the same cartridge?

Cheers!