6.5 Grendel Armor Piercing ammunition data/info...

[stanc]

Again, why bother trying to reinvent what has been shown to work? Just scale up the 5.45 bullet to 6.5mm and be done...

A correction seems in order. I just finished rereading the 5.45x39 section in Emergency War Surgery, which says that the M74 bullet has onset of yaw at 7cm (~3"). That's rather longer than I thought it was when looking at the wound profile drawing.

Perhaps very early, ideal (1") yaw just cannot be achieved with a long, streamlined projectile?

[BluntForceTrauma]

Stan, keep in mind that the "very early, ideal (1") yaw" is the pet theory of a certain individual, or of a certain school of thought.

Early yaw was favored by those thinking we'd be using fragmenting bullets on thin-bodied adversaries in civilian clothing. All well and good. . . .

But it's a trade-off. What happens when an early-yaw bullet must pass through 1" of gear or clothing? I could foresee a situation whereby penetration is negatively affected by too early yaw and/or fragmentation.

Those basing projectile performance conclusions on one gel-test photo, rather than a statistically valid sample of many, many shots, are serious amateurs whose conclusions are probably as sloppy as their methodology.

John

[stanc]

John, we amateurs generally only have access to one gel test photo or wound profile drawing. We have no choice but to base our conclusions on that single piece of evidence.

As for what happens when an early-yaw bullet must pass through 1" of gear or clothing, I can only point to the results of the 6.8mm 115gr HPBT bullet in bare gelatin vs after penetrating a loaded AK mag, shown on page 16 (bottom) and page 17 (top) in: http://www.dtic.mil/ndia/2008Intl/Roberts.pdf

Early yaw may have been favored by proponents of fragmenting bullets, but it also appears to be the only means to maximize terminal effectiveness in non-fragmenting projectiles used by UK and European armies. Posted by Tony Williams in another thread:

The wounding mechanism will therefore mainly be via rapid and reliable yaw and upset on impact: the bullet should start to yaw within about two inches of entering a body...

http://www.65grendel.com/forum/showt...ull=1#post2397

Based on the available evidence of wound profiles -- which AFAIK are representative of statistically valid numbers of gel tests done by Martin Fackler -- it looks to me that onset of yaw in bare gelatin can be no better than ~3 inches, given the best possible FMJ bullet design. Neither the 1-inch "ideal" yaw, nor the ~2 inches desired by Tony, seem achieveable.

BTW, nice job on the new forum header. Are you going to resurrect the old Grendel skull logo?

[BluntForceTrauma]

Stan, my "amateurs" comment was directed at the study, I think it was, that Tony referenced wherein somebody attempted to denigrate the 6.5mm based on the 120 Norma FMJ from Bill's one shot of it.

I definitely want yaw in any potential 65G general-purpose military loadings, but I think the ideal depth of onset deserves more thought.

Skull is pending resurrection. . . .

John

[Tony Williams]

The "yaw after 2 inches" criterion I set was to maximise the soft-target effectiveness. It's a question of degree rather than a yes/no issue; 4 inches is better than 5, 3 inches better than 4 and so on. It might be expressed as "early and reliable onset of yaw" in general terms, with threshold and objective figures to aim for: e.g. threshold is that 80% of bullets must commence yaw within 3 inches of penetration, objective is that 90% should do so within 2 inches" or some such wording.

In principle I like the idea of a very aerodynamic jacket with a hardened steel core (with a blunt penetrating point) set back inside the jacket, with either an air space or lightweight plastic tip filler. This should yaw readily on penetration of a soft target and also penetrate hard targets. The main problem would be getting enough weight into the bullet to achieve the ballistic coefficient needed for long-range performance (or, to put it another way, to reach the required weight the bullet would be so long that stabilisation would become an issue). Tungsten is technically the ideal core material which would make all this possible, of course, but for the cost!

There is obviously a trade-off between weight and shape, in that the more aerodynamic the shape, the lighter the bullet can afford to be for any given BC. Maybe we should take a look at the 5.56mm FABRL and the light-alloy and plastic cored CETME bullet designs, and start from there. After all, if the CETME bullets showed a good BC with a light-alloy core, then we should surely be able to do better with a steel core.

[warped]

Yeah Tungsten is very expensive, that is why the H3G buffers are so damned expensive.

Considering the amount of Tungsten that is used in a wide variety of industries and that there is a fair amount of waste involved it could result in a secondary industry which collects and makes use of the scrap.

Using a sintered core could be one use of this widely untapped resource, another would be to smelt it down and pour it into molds in a very rapid foundry type system. Using green sand you could really just keep making mold after mold with nearly no waste at all.

All you need in a positive form to impress into the tray of green sand, a tray for the lid and there you go!

They use the same process for many other things in automotive and shipbuilding industries.

We save our tungsten scrap for use in making weights for other items, you really hate to waste any of it.

[JASmith]

Yeah Tungsten is very expensive...

Could we consider a dense metal core a "growth factor" option? I don't know for sure yet whether the currently stated needs can't be met with a conventional steel alloy, perhaps with a fair bit of nickel, chrome, etc.

The idea is that we can significantly improve penetration qualities with a dense metal rod of equal weight and in the same shape -- the size just gets reduced. If the subtleties of defeating the ceramics demands a higher velocity, we can get the same sectional density as the steel rod for a substantial reduction in weight, which would afford the opportunity for an increase in muzzle velocity.

This growth capability could add a positive slide or two to the sales pitch.

[JASmith]

The "yaw after 2 inches" criterion I set was to maximise the soft-target effectiveness...It might be expressed as "early and reliable onset of yaw" in general terms, with threshold and objective figures to aim for: e.g. threshold is that 80% of bullets must commence yaw within 3 inches of penetration, objective is that 90% should do so within 2 inches"...

Thanks for the words -- I'll incorporate words to that effect into the soft-target lethality criterion.

In principle I like the idea of a very aerodynamic jacket with a hardened steel core (with a blunt penetrating point) set back inside the jacket, with either an air space or lightweight plastic tip filler. This should yaw readily on penetration of a soft target and also penetrate hard targets...

Can the bullet design be complex enough to allow a three-part construction? I'm thinking of the core you describe, a copper-based cup/driving band, and an aluminum or other light metal alloy wind-screen.

Some aluminum alloys exceed the strength of copper while having about 1/3 the density. This gives one a chance to design a windscreen that will remain intact and attached in soft targets. The low density metal coupled with any void would help shift the center of gravity further aft. Aluminum is opaque enough that it will be readily visible to conventional medical x-rays.

As an aside -- advances in availability of MRI, cat-scan, ultrasound and other medical imaging techniques may give a path allowing the use of plastic. I don't recall the exact language, but it seems to have gone along the lines of prohibiting things not readily detectable.

[stanc]

In principle I like the idea of a very aerodynamic jacket with a hardened steel core (with a blunt penetrating point) set back inside the jacket, with either an air space or lightweight plastic tip filler. This should yaw readily on penetration of a soft target and also penetrate hard targets. The main problem would be getting enough weight into the bullet to achieve the ballistic coefficient needed for long-range performance...

Hmm... it does appear that way. If I figured correctly, scaling up the 5.45mm bullet to 6.5mm would result in a projectile weight of only 90 grains!

Tungsten is technically the ideal core material which would make all this possible, of course, but for the cost!

Cost is not the only problem. Tungsten was eliminated by the US Army from use as the slug material early in the development of lead-free M855, due to environmental concerns (heavy metal pollution). One might think the same restriction would be in Europe, too?

There is obviously a trade-off between weight and shape, in that the more aerodynamic the shape, the lighter the bullet can afford to be for any given BC. Maybe we should take a look at the 5.56mm FABRL and the light-alloy and plastic cored CETME bullet designs, and start from there. After all, if the CETME bullets showed a good BC with a light-alloy core, then we should surely be able to do better with a steel core.

Several years ago I discussed the FABRL and CETME with Frank Hackley, who said:

"The long pointed streamlined bullets did have a number of short comings. First, terminal ballistics [i.e., helmet penetration] were never achieved, primarily because of the bullets light weight. Second, it was assumed that the bullet's armor-piercing ability would be limited because of the shape. And finally, the FABRL bullet made a very poor tracer.

I do not know very much about the CETME, but would not be surprised if some of the same problems prevailed with this round too.

However, there were designs made with the AR-2 shape which included bullets made from copper coated steel and given limited testing but I do not have the test results."

[JASmith]

To expand on the dense metal comment -- I am reasonably confident we can obtain Level III body armor defeat within the general class of cartridge we contemplate. We can also anticipate the need to defeat Level IV body armor. This is likely to mandate the use of dense metals or moving to significantly larger (even larger than the 7.62X51) cartridges.

That's the reason for thinking of dense metal as a "growth" option. I don't know, nor do we need to care today whether the future Level IV defeat round is called GP or AP.

[stanc]

"And finally, the FABRL bullet made a very poor tracer."

That reminds me of what I've seen in other forums: Everybody wants to talk about their concept of the "perfect" bullet for the standard load fired in rifle and carbine, but almost nobody wants to discuss if it's even feasible to make a matching tracer round. Ya gotta have tracer ammo for your sheen guns!

In addition to COL Hackley's comment (above) about a FABRL tracer, I have never seen anything to indicate that the CETME bullet ever had a matching tracer developed. That may be instructive to consider when thinking about using a similar exotic design for the ball projectile.

If the goal can't be achieved with conventional FMJ (or M855A1) configuration, with a steel or steel/copper core, maybe it just can't be done?

[stanc]

To expand on the dense metal comment -- We can also anticipate the need to defeat Level IV body armor. This is likely to mandate the use of dense metals or moving to significantly larger (even larger than the 7.62X51) cartridges.

That's the reason for thinking of dense metal as a "growth" option. I don't know, nor do we need to care today whether the future Level IV defeat round is called GP or AP.

Joe, perhaps I wasn't clear. What do you mean by "dense" metal? Tungsten? Depleted uranium? Lead? If so, none of these meet environmental standards for use on stateside shooting ranges.

A GP round must be (legally) usable for training, as well as war.

In contrast, an AP round can have a core of a dense metal like tungsten, because it will normally be used only in combat in the other guy's country , not in training on our ranges.

[JASmith]

...A GP round must be (legally) usable for training, as well as war.

In contrast, an AP round can have a core of a dense metal like tungsten, because it will normally be used only in combat in the other guy's country , not in training on our ranges.

At the risk of going further into a discussion that might sound like a debate over the number of angels that can alight on a pin-head at the same time, my comments are directed at deferring discussions about dense metal penetrators to a future, unspecified time. One of the techniques to do this is to note that one gets an advantage from using these materials but there are costs associated with using them.

We can take advantage of the dense metal by acknowledging that a rifle cartridge meeting the current notional restrictions on types of materials can grow by upgrading the bullet design if the situation demands.

Hence, we seem to be in agreement that we can postpone discussions about Uranium, Lead, Tungsten, Tantalum, etc. until after we've defined the cartridge and basic bullet. Only after that point and we see a strong indication of the need to routinely deal with Level IV or better armor, should we return to the discussion of dense metals in the bullet.

Even then, there may be some work-arounds. For example, the 20-25 mm grenade launchers may be prevalent by that time. A shaped charge of that diameter would likely make mince meat of the armor.

[Tony Williams]

I wasn't suggesting that we should use CETME-type bullets with a light alloy or plastic core (except perhaps as a tip filler), but simply that we consider adopting something like their external form (which as I understand it gave them excellent flight ballistics) and shove a steel core into it instead.

[warped]

IIRC the 20mm shaped charge and other projectiles were a DARPA proposal back in the 90's