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

[stanc]

4. To replace the 7.62x51 a new cartridge needs to achieve the following:
- to equal the barrier penetration performance of the 7.62mm M80 in terms of overall penetration of a range of media...

How about using 6.5x55 as sort of a surrogate for your proposed round, and conduct barrier penetration tests with it versus 7.62 M80? That way you can get some hard data (at relatively low cost) to validate the theory that your intermediate round can actually equal 7.62 penetration.

Norma markets 6.5x55 ammo loaded with the 120gr FMJ, and IIRC other companies offer 139gr loadings. And on your side of the Atlantic, it might even be possible to get mil surplus AP?

[Tony Williams]

As you are probably aware, gun and ammunition purchasing is a non-trivial issue over here, with all sorts of hoops to jump through to obtain permissions. Basically, rifles can only be bought for hunting or target shooting, you have to apply for specific calibres of rifle and ammunition (and can't acquire anything else without going back to ask for permission again), and AP ammo is effectively banned.

I am in an unusual position in that have permission to own any type of ammo (except HE) in any calibre I want (I need that for my research work) but only in very small quantities for each type, and the price of that is that I don't possess any guns at all. Thanks to some military and other connections I do occasionally get to shoot all sorts of weapons, including those which are banned to civilians in the UK, but I'm not in a position to organise the kind of shooting tests you describe.

[LR1955]

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

Joe:

Negative. The secret is a 130 grain 7.62 whose bullet is about 1.3 inches long.

Saves a bunch of money in terms of re-tooling, less recoil than the issued M-80, longer danger space, 1/3 higher velocity, 1/3 better penetration and 1/3 greater lethality.

I can do the same with a 80 grain 5.56. Retain the parent case for both which saves billions in re-tooling and RDTE.

LR1955

[stanc]

A 130gr 7.62mm spear @ 3800 fps!!! :eek:

What secret sauce are you using, Gene? :confused:

[stanc]

I am in an unusual position in that have permission to own any type of ammo (except HE) in any calibre I want (I need that for my research work) but only in very small quantities for each type, and the price of that is that I don't possess any guns at all. Thanks to some military and other connections I do occasionally get to shoot all sorts of weapons, including those which are banned to civilians in the UK, but I'm not in a position to organise the kind of shooting tests you describe.

Unfortunately, few of us are. All of the photos of you shooting a variety of weapons led me to think that you might be in a position to do such testing. Well, it seemed like a good idea... :o

[stanc]

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...

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.

[JASmith]

How about using 6.5x55 as sort of a surrogate for your proposed round, and conduct barrier penetration tests with it versus 7.62 M80? That way you can get some hard data ...

Stan,

Good idea to get hard exterior and terminal ballistic data relevant to the size of cartridge being considered. We can do that by using handloads with, say, a .260 Remington, or 6.5X55, or any 6.5 mm rifle that can be loaded to the requisite velocities.

In the meantime, back to the requirements list. Are there any additional comments on the threshold and objective statements for item #1? I plan to tweak again in the next day or so.

Cheers!
Joe

[LR1955]

A 130gr 7.62mm spear @ 3800 fps!!! :eek:

What secret sauce are you using, Gene? :confused:

Stan:

Sorry -- look at 1.3 or so inches long.

You see, it is apparent that in this academic discussion, cost is much less important than performance and there are no requirements so anything goes.

No requirements have been stated, no costs. Therefore I am positive a .30 caliber diameter bullet can do everything any other bullet can.

Unless one uses a Grendelf. That bullet will do the trick for sure. Awesome performance.

LR1955

[stanc]

...back to the requirements list. Are there any additional comments on the threshold and objective statements for item #1? I plan to tweak again in the next day or so.

So, item 1 should have:
•Threshold: At least equal the vertex and wind drift seen by the 7.62X51 NATO M80 at 1000 metres when using a 20-inch barrel.
•Objective: Reduce the vertex height by at least 10% and the wind drift by at least 20% compared to the M80.

I have no comments. Out of curiosity, I ran ballistics tables for both calibers, to 1000 yards (~900 meters), assuming 20" barrels, and using BC of the Barnes 6.5mm solid.

7.62 NATO vs 6.5 NATO

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

7.62mm 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 -1.5 43.3 82.5 114.9 139.5 154.4 157.9 147.4 120.0 72.1 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

6.5mm 110gr @ 2650fps BC=0.450
Velocity - fps 2650 2454 2268 2090 1921 1760 1609 1472 1347 1239 1150
Energy - ft-lb 1715 1471 1256 1067 _901 _757 _632 _529 _443 _375 _323
Path - inches -1.5 42.5 80.6 112.0 135.4 149.4 152.2 141.4 114.6 68.6 0.0
Drift - inches _0.0 _0.4 _1.5 __3.5 __6.5 _10.6 _15.9 _22.6 _30.8 40.5 51.9

I must say, the results surprised me.

So, it appears possible to match 7.62 NATO trajectory and wind drift. Next step: Terminal effects.

[JASmith]

Stan,

Reference #49 -- That is pretty cool. It looks like you ran the match for the 20 - inch barrel.

Referring to post #32 and the threshold and objective there:
[INDENT]Threshold:[INDENT]Equal or better the vertex and wind drift of the 7.62X51 M80 at 1000 metres when using a 20-inch barrel.[/INDENT][/INDENT]
[INDENT]Objective:[INDENT]Equal or better the vertex and wind drift of the 20-inch barrel 7.62X51 M80 at 1000 metres when using a 14-inch barrel.[/INDENT][/INDENT]
We can be reasonably sure that when both cartridges have a 14-inch barrel, the trajectories will match about as well -- they will, of course, have larger vertex and drift values. The rub comes when we set the somewhat greater challenge of getting 20-inch performance from a 14-inch tube. I. e., we would require that the 110 gr 6.5 have a 2650 ft/sec muzzle velocity from the shorter barrel.

The velocity estimator suggests that we lose about 150 ft/sec going down to 14 inches from 20. That's equivalent to requiring about 2800 ft/sec muzzle velocity for the 6.5 you posited.

That added velocity is not completely unreasonable if the parent cartridge gets 2650 from the longer barrel using standard propellants and we switch to the blended (e. g. Superformance) propellants -- provided they really work as advertised!!

Also, I like this variant of the objective requirement because it is more tangible than an arbitrary change in vertex and drift values. They, of course, will improve with a cartridge meeting the objective statement, but not necessarily by the numbers I pulled out of the air as place holders.

Cheers!
Joe

[Tony Williams]

You see, it is apparent that in this academic discussion, cost is much less important than performance and there are no requirements so anything goes.

No requirements have been stated, no costs. Therefore I am positive a .30 caliber diameter bullet can do everything any other bullet can.

But it won't significantly reduce the ammo weight or recoil, which are two key requirements.

[Tony Williams]

Referring to post #32 and the threshold and objective there:
[INDENT]Threshold:[INDENT]Equal or better the vertex and wind drift of the 7.62X51 M80 at 1000 metres when using a 20-inch barrel.[/INDENT][/INDENT]
[INDENT]Objective:[INDENT]Equal or better the vertex and wind drift of the 20-inch barrel 7.62X51 M80 at 1000 metres when using a 14-inch barrel.[/INDENT][/INDENT]

My concern with aiming to match 7.62mm/20 inch performance with a 14 inch barrel is that it it will put up the ammo weight and recoil significantly compared with a round which just matches 7.62mm M80 in the same-length barrel. That will hurt the other half of its role, which is to replace the 5.56mm - for which it needs to be as light, and light-recoiling, as it can be. This cartridge needs to be a juggling act to get the right balance of characteristics, and you can't over-specify in some areas without hurting others.

[JASmith]

RE: Post #52:

Tony,

Now you see the beauty of the threshold and objectives duet!

The threshold is what must be accomplished,

The objective can be viewed as a "nice to have" provided the other requirements are met.

Both can be exceeded in a competition for more points as long as all the thresholds are satisfied.

The juggling starts as soon as we have a complete list. Doesn't mean that there won't be a lot of discussion in the interim.

Do you want to tackle item 2 (barrier penetration) next, or would you rather get threshold and objective statements for recoil and ammunition weight next?

Cheers!
Joe

[Tony Williams]

Do you want to tackle item 2 (barrier penetration) next, or would you rather get threshold and objective statements for recoil and ammunition weight next?

I'm happy to leave that to you, Joe!

[LR1955]

But it won't significantly reduce the ammo weight or recoil, which are two key requirements.

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.

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. And I will pump money into recoil reduction until that problem is solved.

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.

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.

Here is a requirement for you guys. Give me a 15 inch ordinate at 500 meters. Issued optics allow a guy to positively ID someone that far (most of the time) but not farther. A 15 inch ordinate means that in most wind conditions a two minute hold ought to offer a better than even chance of a hit without having to spend days trying to teach someone to dope winds which most won't do when under threat.

Give me accuracy potential from rifle / sighting system / and ammo of about 3 inches mean radius at 500 meters. That is a little over two minutes and ought to be possible in terms of production without costing trillions of dollars.

Let a Joe be able to shoot a bullet through the side door of a car with the window rolled down and penetrate at least fifteen inches of ballistic jel representing the width of an adult male. And this happens at 200 meters required, 500 desired. Same for shots through the windshield -- 200 required, 500 desired.

So, there are some realistic requirements for you that are based on what our guys want today.

Now, state your requirements and put them in priority or a developer can not develop what you want.

LR1955

[JASmith]

...If ammo weight is a requirement, you must state your requirements in priority.

Concur -- we should plan on setting points or weighting factors for each requirement. As indicated earlier, we need to be absolutely sure that a threshold can be met, else, we guarantee failure.

If recoil forces are a requirement, state the requirement in terms of energy and then prioritize that requirement too.

Tony, there was a huge amount of discussion on this in MG&A. Is there a way you could summarize and propose a maximum acceptable recoil energy (the threshold), and a "nice to have" level (the objective)? I believe we would either need to specify the rifle mass or allow the rifle mass to be part of the trade space.

...state 'same vertex as M-80, same Ke at 1K meters' without even being able to state why 1K is required...

At the risk of putting words in Tony's mouth (keyboard??), the MG&A forum indicates that the 1000 meter range is for GPMG applications. The 7.62 M80 is the existing standard, so equaling or improving its performance is viewed as necessary.

On the political side, I tend to concur that meeting or bettering 7.6X51 performance is necessary.

Your comments are exactly right from the technical side. But we need to find testable [I]and[I] achievable standards,

What small arms optic allows anyone to see and ID an enemy that far?

Concur -- many of the requirements for the standard rifle/carbine are not yet well defined. This is one of the reasons I expect the list of requirements to grow. Projected ROE and sighting systems for the average soldier will impact them, and, may possibly need to be explicitly called out.

Here is a requirement for you guys. Give me a 15 inch ordinate at 500 meters. Issued optics allow a guy to positively ID someone that far (most of the time) but not farther. A 15 inch ordinate means that in most wind conditions a two minute hold ought to offer a better than even chance of a hit without having to spend days trying to teach someone to dope winds which most won't do when under threat.

I assume the 15 inch ordinate (vertex?) is based on a center hold on a 30-inch torso. We need to be careful to not ask for the impossible. Not even the CorBon load for the 123 gr Scenar in a 24-inch barrel chambered for the .260 Remington will get that (the range is 416 meters per JBM calc).

If one assumes a center hold on the torso but allows hits lower, then the .260 Rem gets a "max point blank range" of 490 meters.

The 'old' M855 with a muzzle velocity of 2790 ft/sec (14.4 in bbl) gets a max range of 383 meter for a 15" max ordinate and 446 meters for bullet flight 15" above and 15" below the sight line.

So, one would need to think about how to attain a useful range of 500 meters through a combination of raw exterior ballistics and sighting systems.

How much should we bring optics and sighting systems into the requirements? How far can we go by simply discussing the ROE, optics, etc. as background in the overall document and as a more detailed discussion for the relevant requirement?

Give me accuracy potential from rifle / sighting system / and ammo of about 3 inches mean radius at 500 meters. That is a little over two minutes and ought to be possible in terms of production without costing trillions of dollars.

For most of us, this would be a no-brainer. Can you expand to show the significance 3" mean radius when the torso is about 18" across?

Let a Joe be able to shoot a bullet through the side door of a car with the window rolled down and penetrate at least fifteen inches of ballistic jel representing the width of an adult male. And this happens at 200 meters required, 500 desired. Same for shots through the windshield -- 200 required, 500 desired.

Good start -- details need to be worked.

If I recall correctly, items #2 & #5 addressed this last point.

I'll expand my thoughts a little in my next post - this one is a tad long...

[JASmith]

This next step addresses terminal performance (items #2 & #5 in Tony & Gene's list) --

The question of terminal performance is the emotional driver that leads us to where we are now. On the technical side, Tony points out that recoil is critical, Gene improving hit probability, and so on.

Gene suggests that:

LR1955]
Let a Joe be able to shoot a bullet through the side door of a car with the window rolled down and penetrate at least fifteen inches of ballistic jel representing the width of an adult male. And this happens at 200 meters required, 500 desired. Same for shots through the windshield -- 200 required, 500 desired.

We need to expand this and to ask if other barrier perforation thresholds are needed. Cinder blocks, unfilled, or filled, come to mind...

Starting with the door-frame, here's an extract from an earlier post that illustrates some of the complications:

(From Post #21) ...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......

My caution is that the transition from truck-stopping, armored bad guy incapacitation, etc. to testable targets is not a trivial step.

The door frame and windshield scenario is a common one. Let's check on existing requirements practice in this area.

Does anyone have insight into what RARDE, Picattiny, etc. are using?

[stanc]

Does anyone have insight into what RARDE, Picattiny, etc. are using?

This is the most that I've seen:
http://www.dtic.mil/ndia/2006smallarms/gandy.pdf

P.S. Some info on steel-core "green" bullet terminal effects:
http://www.dtic.mil/ndia/2006smallarms/mauritzson.pdf

[JASmith]

Stan,

Thanks! This confirms that the standards exist. The NATO truck target is close to Gene's car door in concept. Gene's is likely more challenging.

Also important, these tests are looking at the difference in performance of particular bullet designs. They also point out the complexity of assessment even within a single cartridge. I submit that the bullet design challenge is complex enough that one could consider this a separate, but related, sport.

Tony has already indicated the mechanism for lethality. I wonder if we could identify or generate a parallel document addressing requirements for bullet performance? The link back to the cartridge would then be specified energy and momentum per square millimeter coupled with a minimum bullet length.

This way we might be able to avoid over-complicating the whole effort.

Cheers!
Joe

[stanc]

Tony has already indicated the mechanism for lethality. I wonder if we could identify or generate a parallel document addressing requirements for bullet performance? The link back to the cartridge would then be specified energy and momentum per square millimeter coupled with a minimum bullet length.

This way we might be able to avoid over-complicating the whole effort.

Ha! I think it's already way over-complicated.

IMO, the best way to present this idea to the decision makers is via the "picture is worth 1000 words" method. Instead of writing a multitude of documents (not that it hasn't been fun ), show the results of terminal effects for the different calibers. And demonstrate the difference in such factors as controllability, hit probability, etc.

Of course, this would require actually getting the requisite weapons, modifying and shooting them in "hands on" test and evaluation... :o