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

[JASmith]

...There is a problem in defining a barrier based on a steel of any sort. Barriers are not monolithic (if that is the word to use). For example, we had to stop using RHA plate as a testing material when armor started to become laminates of different types and alloys of things... ...So, you have to decide what is more important -- penetration of hard things or terminal effects on humans.

Gene,

The following expansion is not intended to make the problem of defining terminal performance seem impossible. It is not. The real issue is how one transitions from the anecdotal to the measurable and testable requirements.

As you've indicated, we need to ask ourselves what the bullet needs to do. Yes, living flesh behind barriers (or with no barriers) is one class of terminal effects. What kind of response do we want if the target is a moving vehicle? Or a low-flying helicopter? Low flying aircraft?

These and more represent the kind of engagements we know that folks using small arms get into. How important is one or another. I can surmise the pucker factor gets significant when one is trying to stop a bomb-laden truck with an inadequate cartridge.

But, what does the bullet need to do to stop that truck?

• Kill the driver?
  
• Kill the engine or power train?
  
• Deflagrate or detonate the bomb?
  

Optimizing for any one of these mechanisms will seriously impact the resulting bullet, cartridge, and weapon system design. It will also influence training the soldiers need to attain the goal of stopping the truck. (Oh, I forgot to ask how quickly the truck needs to be stopped -- an immediate stop begets images of 105 howitzers and HELLFIRE missiles.)

Make sure the design target results in a weapon that will pass the Admiral's test. Yes there are examples of the failures. Usually attributable to an overenthusiastic PM pushing the design requirements down to the absolute minimum. "Absolute minimum" performance specifications makes the design vulnerable to multiple minor oversights. On the other hand, going to an overly robust design spec makes the ensuing device too heavy, costly, or unwieldy to be adopted.

In having designed or worked with more design targets in various applications in the intervening years, I have learned the importance of keeping the design target simple enough to allow repeatable fabrication and testing.

An example of unintentional violation of the simplicity rule occurs when one specifies "X mm penetration in ballistic gel after perforating a truck door frame." The hiccup occurs when you actually use the door frame in developmental testing, one can be led astray by the inevitable interaction with the things that are inside the door frame.

So the apparently obvious solution is to replace the door frame with sheets of door frame material with the appropriate air gap. This makes an incomplete statement, because one needs to also specify the frequency the bullet is likely to encounter something besides air in the space between the exterior and interior sheets. We likely need to make this statement rather than requiring that the bullet pass through the braces, fasteners, door latches, window cranks and gears, etc. The added requirement would likely make the bullet way too big for normal infantry applications.

Next, one needs to state the obliquity at which the bullet must be able to attain the specified penetration into the ballistic gel, or engine block, etc. behind the "door frame." Oops! the increased angle means that the interior stuff gets hit more often. How often?

Aw heck, the off-angle impact makes my bullet start to tumble and the increased travel time makes the bullet turn enough that it won't penetrate the second sheet.

And so on...

If you've gotten this far in the note, its time to take a step back and recognize that your request is absolutely on track. We need to specify more than one target and assign relative importance. My caution is that the transition from truck-stopping, armored bad guy incapacitation, etc. to testable targets is not a trivial step.

Cheers!
Joe

[stanc]

Any rifles and MGs designed for 7.62x51 should be adaptable to the new round.

Of course. However, it would be somewhat illogical to convert the FN FAL and FN MAG, for instance, to the intermediate cartridge, as the only weight savings would be in ammo, not the weapons.

I suggested the FN pair simply because they are the two most obvious ones, being recently designed, in military service, and lightweight for the calibre.

Understood.

[6mm SAW] was a good cartridge for its purpose, but I think that it is probably too small and lacking in power to be a credible replacement for the 7.62x51.

I'm sure you're right about that. But, although I initially started out years ago proposing a single caliber to replace both 5.56 and 7.62 NATO ( http://www.g2mil.com/6mm_optimum_cartridge.htm ), I've since concluded that a two-caliber system probably makes more sense, all things considered. Plus, I don''t see 7.62x51 going away anytime soon; it works well enough insofar as target effects, and there is such a multitude of weapons chambered for it that it doesn't seem cost-effective to try to replace.

Don't forget that I see a new conventional round as being a half-way stage to something like LSAT. I believe that it is necessary to prove the intermediate round concept with hardware people can take out and use, before committing to introduce a whole new technology in the calibre. That means a conventional development path using existing weapons.

If LSAT fails for any reason, then other ways of lightening the load can be tried with the new conventional round - stainless steel cases or part-polymer ones like this one: http://www.pcpammo.com/index.html

Yes, I had forgotten that. Given that goal, your approach is logical.

[stanc]

What you guys need to do is to define the barriers that you require penetration. One of them will be some level of body armor as that stuff is appearing more regularly.

Where? I haven't heard of any of our current enemies making significant use of body armor. AFAIK, the only people who use hard body armor are our allies and others whom we are very unlikely to fight. I see no good reason to be concerned about defeating Interceptor-type armor, and soft armor can be penetrated by ordinary ball ammo.

Another will be sheet metal and automotive glass separated by some specific amount of space such as found for car and truck doors. A third may be some type of construction material if any is common throughout the world. Not sure of any others but they must be common throughout the world.

So, you have to decide what is more important -- penetration of hard things or terminal effects on humans.

Both are important. At least the military tests for both. Here's some of the barrier testing: http://www.dtic.mil/ndia/2008Intl/Lucid.pdf

[JASmith]

Stan,

Gene has a point -- we do need to do at least a little "red team" work in developing the notional requirements list. The value is that, if adopted, the new cartridge will be around for at least a decade, more likely 20 to 30 years to provide space for the replacement technologies to materialize and mature. This gives plenty of time for our future adversaries to develop new tricks. At the same time, we need to avoid being obsessively over-exuberant in laying on challenging requirements -- that's the fastest way to kill the project!

My sincere hope is that Tony or one of his associates has insight into the UK MoD mindset of what a new cartridge should be required to do. I will also admit that much of the discussion in his forum deals with the same notion that the current weapons are just fine thank you. With a variant of come back and talk to us after a real requirement develops (sounds like don't call us -- we'll call you.).

[LR1955]

[quote=Tony Williams]A few weeks ago someone asked me to do this. So this was my first-draft shot at it:

OUTLINE SPECIFICATION FOR A LIGHTWEIGHT HIGH-PERFORMANCE SMALL-ARMS CARTRIDGE

OK -- here you go.

I eliminated the problem statement because it lacks references. I know it is a part of the research process to state the problem but in this situation, it would lead to more arguments, which are not the focus. The focus is to state specific requirements. Therefore, here is a listing of the requirements I get from Tony with my comments in italics (I hope).

1. To match the retained energy, vertex height and wind-drift performance of the 7.62mm M80 ball round at 1,000 metres.

This is a clearly stated requirement but I would ask what is so important about equaling the exterior ballistics of M-80? If one can only equal the performance, why a new cartridge?

2. To equal the barrier penetration performance of the 7.62mm M80 in terms of overall penetration of a range of media while maintaining its trajectory ("blind to barriers")

The barrier or barriers and media need to be specified along with ranges where the same must be penetrated along with residual effects or the entire project will lack focus.

3. To exhibit rapid and reliable yaw on impact with ballistic gel representing a body, ideally commencing within 50mm of penetration and completing bullet upset within 250mm.

This needs to be stated in terms of range and intermediate barriers.

4. 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%

If this is to be a requirement then a standard rifle must be identified from which someone can determine what 60% means. It is not hard – just state the rifle that will be used.

5. To deliver a substantial improvement at all ranges over the 5.56mm M855 in barrier penetration and trajectory maintenance through barriers.

‘Substantial’ must be clearly defined.

5. To deliver a substantial and reliable improvement in terminal effectiveness as measured in the size of the permanent channel created in ballistic gel tests within the 50-250 mm penetration zone, regardless of the bullet angle of yaw on impact.

Again the terms ‘substantial’ and ‘reliable’ must be clearly defined.

7. 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%

What standard rifle will be used and why?

8. The standard ball bullets used to achieve the performance requirements must comply with European legal interpretations of the Hague and Geneva Conventions governing military ammunition, i.e. they must be designed not to expand or fragment and any jacket must fully enclose the tip.

9. The standard ball bullets should be made of lead-free materials and be suitable for economical mass production.

OK but now, you have to state the cost of the bullet. Must not cost more than X amount of money.

10. The cartridge designs should be optimized for use in conventional military magazine-fed and belt-fed automatic weapons, so that existing gun designs can be adapted to use them.

Again, the key word is ‘adapted’. This needs to specifically defined in terms of parts.

11. The cartridge case design should be suitable for manufacture in a range of materials, including brass, steel and part-polymer.

[JASmith]

Gene,

Good summary. I think we can build on this!

As you've indicated, terms like "substantial" will need to be replaced with metrics. Yes, making the requirements relative to the 7.62X51 makes the process more straightforward.

Need a good definition of "barrier blind" because no bullet will go through a barrier without seeing at least a little upset or tipping. Some designs can minimize but they'll look more like wadcutters.

There are claims that the M855 penetrates at least some barriers better than does the 7.62 M80. This might suggest that 2 & 5 be combined to read "...equal or better both..."

The second item #5 looks like it wants to be in comparison with the M855.

Will ponder more, review others' comments and comment as needed.

[Tony Williams]

Thanks for your comments Gene - a few responses:

1. To match the retained energy, vertex height and wind-drift performance of the 7.62mm M80 ball round at 1,000 metres.

This is a clearly stated requirement but I would ask what is so important about equaling the exterior ballistics of M-80? If one can only equal the performance, why a new cartridge?

The new cartridge would make a significant saving in MG ammo and gun weight by being lighter and less powerful, reducing the burden on the soldier. But if the long-range ballistics cannot equal the M80, I don't believe that it would be accepted as a replacement for it.

2. To equal the barrier penetration performance of the 7.62mm M80 in terms of overall penetration of a range of media while maintaining its trajectory ("blind to barriers")

The barrier or barriers and media need to be specified along with ranges where the same must be penetrated along with residual effects or the entire project will lack focus.

Agreed. But the main point remains - that whatever barriers are chosen, the new round should penetrate them as well as M80, for the same reason as given above: if it is perceived to be inferior to the M80, then it probably won't be able to replace it.

3. To exhibit rapid and reliable yaw on impact with ballistic gel representing a body, ideally commencing within 50mm of penetration and completing bullet upset within 250mm.

This needs to be stated in terms of range and intermediate barriers.

Agreed. My spec was a first draft of an outline, a full military spec would need to be more detailed.

4. 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%

If this is to be a requirement then a standard rifle must be identified from which someone can determine what 60% means. It is not hard – just state the rifle that will be used.

OK, although the point remains - whatever rifle is chosen (let's take the SCAR H as that's already been mentioned, although a member of the AR-10 family would do as well - or an HK 417) should be the same in every respect except calibre, to allow direct comparisons to be made.

5. To deliver a substantial improvement at all ranges over the 5.56mm M855 in barrier penetration and trajectory maintenance through barriers.

‘Substantial’ must be clearly defined.

5. To deliver a substantial and reliable improvement in terminal effectiveness as measured in the size of the permanent channel created in ballistic gel tests within the 50-250 mm penetration zone, regardless of the bullet angle of yaw on impact.

Again the terms ‘substantial’ and ‘reliable’ must be clearly defined.

On reflection these requirements are probably not necessary, since in the great majority of cases (except for plate armour) anything that can match the M80's penetration and wound channel size should easily beat M855.

7. 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%

What standard rifle will be used and why?

See answer above...

9. The standard ball bullets should be made of lead-free materials and be suitable for economical mass production.

OK but now, you have to state the cost of the bullet. Must not cost more than X amount of money.

OK, although that's not something I have any expertise in calculating.

10. The cartridge designs should be optimized for use in conventional military magazine-fed and belt-fed automatic weapons, so that existing gun designs can be adapted to use them.

Again, the key word is ‘adapted’. This needs to specifically defined in terms of parts.

The key word for me is existing gun designs...in other words, not that existing guns would necessarily be adapted on a large scale (although they presumably could happen if it made financial sense), but than an existing design (e.g. AR-10) could be manufactured with suitable changes to use the ammo.

[LR1955]

Tony / Joe:

It appears that no one is willing to be specific about requirements. Or capabilities for that matter.

If you guys do not specifically state the intermediate barriers, penetration and residual to include lethality, it is not possible to design a bullet or cartridge. Simply impossible.

So, once again please state the requirements for this round of ammunition in terms that can be measured.

I will be happy to give a set of requirements. They aren't hard to come up with given all the criticism of the current ammunition and weapons. I don't want to because it is your show and no matter what I come up with, you guys will head down your own path.

Got to do something important right now so hopefully you or Joe will come up with something solid that someone can go by.

LR1955

[Tony Williams]

I will be happy to give a set of requirements. They aren't hard to come up with given all the criticism of the current ammunition and weapons. I don't want to because it is your show and no matter what I come up with, you guys will head down your own path.

I certainly do not regard this as "my show". I have been arguing for this over a long period, but so have many others. To get anywhere with this will require co-ordinated action by many different people with different contributions to make.

I see my contribution as providing an historical perspective, promoting the arguments for a general-purpose rifle/MG round (gathered from studying recent military sources in both the US and UK) and sketching out what it might be expected to do and what it could look like. I have no military experience neither am I a ballistician or cartridge designer. I believe that it is those with recent military experience at the sharp end who should be consulted over the requirements, with cartridge designers providing a reality check to ensure that the requirements are deliverable, and then specifying the design of the bullet and cartridge best able to deliver the requirements.

If the outcome is a better small arms system for our soldiers, then I will be well pleased to have made a contribution, and I don't care who gets the credit.

So by all means please do give your take on the requirements - any informed input is valuable.

[JASmith]

Tony / Joe:

It appears that no one is willing to be specific about requirements...

One of the reasons for the reticence is some of us are hesitant about displaying our naivete...

Flip responses aside, you really have made an excellent start. One of my mentors from years ago suggested a spiral approach to getting at a conclusion when the topic is particularly complicated.

Your expansion of Tony's list is something we can work with to spiral in to the specifics. Shotgunning the list is likely to lead to a lot of wandering. I propose that we start with the first item, check for redundancy with other items, and then beat on it until the specificity, testability, and reasonableness tests are satisfied. After that, we tackle #2, and so on. Other items can be added as we work down the list.

So, let's start with #1:

Originally Posted by LR1955
1. To match the retained energy, vertex height and wind-drift performance of the 7.62mm M80 ball round at 1,000 metres.

This is a clearly stated requirement but I would ask what is so important about equaling the exterior ballistics of M-80? If one can only equal the performance, why a new cartridge?

I resonate with Gene's critique on this point, but understand the hesitation to ask for more. The balance of minimum acceptable versus desired performance normally handled in requirements documents by specifying a threshold and an objective performance level. Failure to attain the threshold level means that the candidate is automatically rejected. The objective level is what the requirements team would really like to see within reasonable technical limits.

So, item 1 should have:

• Threshold: At least equal the vertex and wind drift seen by the 7.62X51 NATO M80 at 1000 metres.
  
• Objective: Reduce the vertex height by at least 10% and the wind drift by at least 20% compared to the M80.
  

The 10% and 20% values are place-holders for now. Part of our discussion should explore what is possible within the projected case volume and bullet design limits.

Second, I'm sure that we are tacitly assuming the same barrel lengths in our discussion. We need to specify that so that someone doesn't try to compare the performance of the 7.62 in a 20" barrel with that of the new cartridge in a 14.5" barrel. (Now if we want that we need to so state, but bear in mind the velocity difference puts a significant handicap on any new design.)

I've run out of time for this morning, but we will need to check for redundancy against the 5.56...

[stanc]

The balance of minimum acceptable versus desired performance normally handled in requirements documents by specifying a threshold and an objective performance level. Failure to attain the threshold level means that the candidate is automatically rejected. The objective level is what the requirements team would really like to see within reasonable technical limits.

I'm glad you brought that up, Joe. I was going to do it, but darned if I could remember the "threshold" term.

Second, I'm sure that we are tacitly assuming the same barrel lengths in our discussion. We need to specify that so that someone doesn't try to compare the performance of the 7.62 in a 20" barrel with that of the new cartridge in a 14.5" barrel.

Who would do such a thing? Actually, I think it's inevitable, because 20" is the standard barrel length for the UK's L85 rifle, but 14.5" is standard for the US Army's M4 carbine.

IIRC, I got into a discussion on the old forum about this. Comparing the same barrel lengths places an artificial limitation on the matter, whereas in the real world, different barrel lengths are used.

For instance, why would one compare 7.62x39 and 5.56x45 in same length barrels, when on the battlefield they use different lengths?

The US Army seems set on the idea that weapon overall length not exceed that of the M4, so much so that the XM8 was fitted with a 12.5" tube! :p

Except in the case of the Mk48 machine gun, is there any reason to think the new cartridge would be used in the same (20-24") barrel lengths as standard-issue 7.62mm weapons? Perhaps the Brits would develop another 20" barrel bullpup in the new caliber, but is there any reason to think that the US Army would abandon the carbine and its circa 14" barrel?

[JASmith]

Stan,

Your point is well taken.

The proliferation of shorter barrels suggests that we can reasonably expect that the standard barrel length for the new cartridge to be less than 0.5 metres.

The performance reputation of the 7.62X51 is in a .5+ metre (20-24 in.) barrel. Many, if not most, of the complaints about the 5.56 are partly a result of its use in the 14.5 in (0.37 metre) barrel.

So, if we hypothetically decided that we must use a .308 in bullet, the cartridge would have to be larger than the 7.62X51mm NATO in order to just match the trajectory with, e. g., the M80 bullet.

So, an alternative threshold might be "Equal or better the vertex and wind drift of the 7.62X51 M80 at 1000 metres when using a 20-inch barrel." The complementary threshold statement might then be "Equal or better the vertex and wind drift of the 7.62X51 M80 at 1000 metres when using a 14-inch barrel."

For Tony: Does this alternative fit your vision better?

Cheers!
Joe

[bwaites]

Wow! While you guys look for the magical bullet and cartridge combination that will match .308 ballistics from a 14 inch barrel the hordes have stormed the gates and overtaken you! LOL!!

Good luck with this search, because its simply impossible. You cannot launch a projectile from a shorter tube and match velocity and external ballistics unless you increase powder capacity. Increasing powder capacity increases weight, but more importantly, increases recoil, putting you back at square one!

I'm all for improving what is available to our Joes, but this is an impossible task without changing the paradigm and using some other type of cartridge. It simply won't and can't happen using traditional brass and bullets.

What you are proposing is a shift as radical as the shift from black powder to smokeless.

[stanc]

Wow! While you guys look for the magical bullet and cartridge combination that will match .308 ballistics from a 14 inch barrel the hordes have stormed the gates and overtaken you! LOL!!

Aha! So that's who was tromping up and down my back!

Ya know, that's not only quite rude, but it makes precise aiming rather difficult...

[Tony Williams]

The US Army seems set on the idea that weapon overall length not exceed that of the M4, so much so that the XM8 was fitted with a 12.5" tube! :p

Makes you wonder why they are so dead set against bullpups, considering that you get an 8 inch advantage in barrel length for the same length gun...

I am happy for a barrel length of 20 inches to be specified when making comparisons with the 7.62mm, since in reality guns being used at anything approaching 1,000 metres would probably have such a barrel. (Although having said that, the British troops seem delighted with the 7.62mm L129A1, which has a 16 inch barrel. But then, their only alternative is an SA80...)

It seems reasonable to specify a 14.5 inch barrel when making comparisons with 5.56mm. That actually makes the use of both sets of comparisons quite sensible.

[JASmith]

Wow! While you guys look...

The secret sauce is a smaller caliber than 7.62...

[JASmith]

...I am happy for a barrel length of 20 inches to be specified when making comparisons with the 7.62mm, since in reality guns being used at anything approaching 1,000 metres would probably have such a barrel...It seems reasonable to specify a 14.5 inch barrel when making comparisons with 5.56mm. That actually makes the use of both sets of comparisons quite sensible.

We might be approaching the trajectory question a bit awkwardly.

A way of looking at this might be to ask that the rifle/carbine has a point blank range (based on the average size of the torso) that is equal to or better than the 5.56 and that the GPMG application has the direct 7.62 comparison.

[Tony Williams]

We might be approaching the trajectory question a bit awkwardly.

A way of looking at this might be to ask that the rifle/carbine has a point blank range (based on the average size of the torso) that is equal to or better than the 5.56 and that the GPMG application has the direct 7.62 comparison.

Yes, but I was also thinking that the new round would replace 7.62mm in the semi-auto DMRs like the M110 and M14EBR.

Clearly, it would make sense with one general-purpose round to have the DMR simply being a longer/heavier barrel version of the standard rifle/carbine.

[JASmith]

Yes, but I was also thinking that the new round would replace 7.62mm in the semi-auto DMRs like the M110 and M14EBR.

Clearly, it would make sense with one general-purpose round to have the DMR simply being a longer/heavier barrel version of the standard rifle/carbine.

Yup!!!

[Tony Williams]

A follow-up thought - given the likely weight of the DMR and the reduced recoil of our general-purpose cartridge, it could also be given selective fire to act as an automatic rifle.